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Review

Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables

by
Spyridon A. Petropoulos
1,*,
Shirley L. Sampaio
2,
Francesco Di Gioia
3,
Nikos Tzortzakis
4,
Youssef Rouphael
5,
Marios C. Kyriacou
6 and
Isabel Ferreira
2,*
1
Crop Production and Rural Environment, Department of Agriculture, University of Thessaly, 38446 Nea Ionia, Greece
2
Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253 Bragança, Portugal
3
Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA
4
Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, 3603 Limassol, Cyprus
5
Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy
6
Department of Vegetable Crops, Agricultural Research Institute, 1516 Nicosia, Cyprus
*
Authors to whom correspondence should be addressed.
Antioxidants 2019, 8(12), 617; https://0-doi-org.brum.beds.ac.uk/10.3390/antiox8120617
Submission received: 16 November 2019 / Revised: 30 November 2019 / Accepted: 3 December 2019 / Published: 4 December 2019
(This article belongs to the Special Issue Antioxidant Properties of Natural Products: A Themed Issue in Honor of Professor Isabel C.F.R. Ferreira)
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Versions Notes

Abstract

:
During the last few decades, the food and beverage industry faced increasing demand for the design of new functional food products free of synthetic compounds and artificial additives. Anthocyanins are widely used as natural colorants in various food products to replenish blue color losses during processing and to add blue color to colorless products, while other compounds such as carotenoids and betalains are considered as good sources of other shades. Root vegetables are well known for their broad palette of colors, and some species, such as black carrot and beet root, are already widely used as sources of natural colorants in the food and drug industry. Ongoing research aims at identifying alternative vegetable sources with diverse functional and structural features imparting beneficial effects onto human health. The current review provides a systematic description of colored root vegetables based on their belowground edible parts, and it highlights species and/or cultivars that present atypical colors, especially those containing pigment compounds responsible for hues of blue color. Finally, the main health effects and antioxidant properties associated with the presence of coloring compounds are presented, as well as the effects that processing treatments may have on chemical composition and coloring compounds in particular.

1. Introduction

Root vegetables display various colors which usually depend on the presence of three major classes of compounds, namely, flavonoids, betalains, and carotenoids, which they may define their visual appearance and consumer perception [1,2]. Anthocyanins are flavonoids responsible for the different shades of plant epidermal tissues such as purple, blue, red, and pink colors, aiming at attracting pollinators and contributing to the overall plant antioxidant mechanisms under abiotic and biotic stress conditions [3]. They also participate in several physiological processes of the plant, including photosynthesis and plant interactions with the environment [4]. They are produced via the phenylpropanoid pathway and the conversion of leucoanthocyanidins into colored anthocyanidin and glycoside derivatives via anthocyanidin synthase and other enzymes [1,5]. The great number of anthocyanins isolated in nature so far and their high structural variation across plant species raised research interest in these compounds during the last few years in search of novel natural colorants [6,7]. The structural variation of anthocyanins is related to the substitution of hydroxyl and methoxyl groups in the B ring, glycosidic substitution at positions 3 and 5 of the A and C rings, and the possible acylation of glycosidic substitutes with aliphatic and cinnamic acids (Figure 1 and Figure 2) [6]. These structural differences may infer significant variations in the biological activities and antioxidant properties of vegetable products. For example, Oki et al. [8] suggested that antioxidant activities of purple sweet-potato extracts from peonidin-rich cultivars were attributed to anthocyanins, whereas, in those extracts from cyanidin-rich cultivars, the antioxidant capacity was due to the phenolic compounds. Other compounds that transfuse blue color in nature are quinones, quinodes, and various alkaloids which are usually present in fungi, bacteria, and in the animal kingdom [9]. Quinones and quinodes include carbonyl groups within aromatic rings, and they also show a great variation from a structural point of view [9], while alkaloids contain nitrogen atoms and are divided into several distinct classes, including pyridine alkaloids, phenazine alkaloids, and linear tetrapyrrole and indole alkaloids, with different coloring attributes [9].
On the other hand, carotenoids are mainly responsible for yellow and orange color with several distinct compounds being detected so far in various vegetables [6,10,11,12], while betalains such as betacyanins and betaxanthins are also important for the violet and yellow pigmentations, respectively [13]. The main detected carotenoids are β-carotene and lycopene, which are unsaturated hydrocarbons, and they differ in terms of the β-rings, where β-carotene molecules have both ends (Figure 3), and they usually present synergistic effects [14]. Both are fat-soluble, and the number of conjugate double bonds in their structure is closely related to their superoxide inhibitory effect [15,16]. Betacyanins and betaxanthins differ in the moiety derived from betalamic acid, as towel as the fact that betaxanthins are produced from the condensation of betalamic acid with amino acids and they never show glycosidation, whereas betacyanins are the result of condensation of betalamic acid with imino compounds (Figure 4) [17,18]. Further differences are observed within each main class of betalains, namely, betacyanins and betaxanthins, with several structures identified resulting in different individual compounds with different absorption and stability capacity [19]. In particular, the various betacyanins are differentiated through the glycosyl groups attached to the o-position of the cyclo-dopa moiety [20], while betaxanthins are differentiated through the conjugated moiety of betalamic acid (amino acids or amines) [20]. The main pigments isolated in the various root vegetables are presented in Table 1.
The first coloring agents used in food products to improve their visual appearance were produced from natural sources; however, the high cost for the production of these coloring agents, the variation in color shades due to the inert variability in natural matrix compositions, and the increasing needs of the market resulted in the use of synthetic compounds originally derived from coal tar and then produced from petroleum and crude oil (e.g., FD&C blue No. 1 and blue No. 2) [9,59]. The consumer concerns about additives and synthetic compounds, amplified by the reports regarding the health risks and the environmental impact associated with these compounds [60,61,62], necessitated the shift to the root food industry dyes; recently, the food and beverage industry is seeking natural coloring agents that could substitute synthetic dyes and coloring additives [63,64]. The colorant content of root vegetable products is associated with various health benefits including the prevention of modern chronic diseases [65,66,67]. However, they are often highly concentrated in the epidermal layers and skin tissues which are commonly discarded during domestic processing or in industrial applications [68,69,70]. For this reason, the research interest in obtaining natural pigments and bioactive compounds from agro-food waste is gaining ground within the context of circular economy and the sustainable use of natural resources [70,71,72,73,74]. There are also several cases where colorants can be found in high concentrations in the flesh due to the presence of pigments in parenchymal cells, increasing the antioxidant capacity and functional value of these products (e.g., potatoes, beets, carrots, and other root vegetables having colored flesh) [3]. Pigment compounds contribute to the overall antioxidant capacity in a dose-dependent and compound-specific manner [75,76,77], although the bioavailability and the absorption mechanisms within human body still need to be addressed [78]. Notwithstanding the genetic background of each species and/or cultivar, color attributes may be modulated by environmental factors such as the light and temperature conditions, through biotic and abiotic elicitors that may affect chemical composition, hormonal signaling, and enzymatic activities. Although not directly exposed to solar radiation, the pigmentation of root vegetables developing belowground may be indirectly modulated by the level and quality of radiation to which the aboveground plant is exposed [79]. In addition to pre-harvest factors, post-harvest conditions and processing methods may have an impact on bioavailability and biostability of natural matrices and coloring compounds [13,80,81]. Anthocyanins in particular are considered a good option as natural coloring agents due to their low toxicity and the wide range of health effects they present [82]. However, the stability and bioavailability of anthocyanins are affected by several factors (chemical structure and concentration, pH of food matrix, temperature, light, presence of co-pigments, enzymes, and metallic ions, among others), which determine the processing method specificity, and which need to be considered before using these compounds as natural coloring agents in the food industry [83,84]. Moreover, the association of structural differences with biostability and bioavailability is further reflected in the biological activities of these compounds, since, for example, acylated forms are less prone to degradation due to pH variations [14,85]. Therefore, although, for some species, there are already defined protocols for the extraction and processing requirements for obtaining natural colorants (e.g., black carrot, beet root colorants) [71,86,87,88], there is still a gap in the literature for other colored vegetables which could prove valuable candidates for yielding coloring agents.
The present review aims to present the main colored root vegetable crops, focusing on cultivars with colors atypical for the species. Special attention is given to blue- and purple-colored vegetables since natural colorants of these shades are less common in nature and are highly sought by the food industry, since blue shades are more difficult to replicate in food and beverages due to the susceptibility of coloring compounds to external factors (e.g., pH of the food matrix, extraction conditions). Furthermore, the main compounds responsible for uncommon colors are presented, as well as their antioxidant capacity and health-promoting effects. Finally, the effects of processing treatments on color stability are addressed. The presented information in this review was obtained from worldwide accepted databases such as Scopus, ScienceDirect, PubMed, Google Scholar, and ResearchGate, using the respective names of the studied species (both common and Latin names) and the additional terms of the main colorants and “health effects” as keywords.

2. Main Colored Root Vegetables

2.1. Potato

Potato (Solanum tuberosum L., Solanaceae) is the third most important food crop in the world, after wheat and rice [89]. In addition to its nutritional and calorific value, potato varieties also offer bioactive compounds with beneficial effects for human health, such as phenolic compounds and carotenoids, among others [12,23]. Several reports highlighted the beneficial effects of antioxidant-rich potatoes against various diseases, such as cardiovascular diseases [90] and various types of cancer [91,92]. Although yellow- and white-fleshed tubers are the most commonly used ones throughout the world, potato has the highest genetic diversity among cultivated species, with approximately 5000 known varieties with broad variability in terms of flesh and skin color [93]. Red- and blue-fleshed potatoes are particularly rich in phenolic compounds, presenting about three times higher amounts of total polyphenolic content than traditional yellow-fleshed tubers, as well as two to three times higher antioxidant activity [12,23,24,94].
Acylated forms of anthocyanins were reported to be the main compounds responsible for the red and purple flesh color of potatoes [94]. In particular, the deep-purple color of potato flesh and skin is associated with the presence of petunidin derivatives, although studies on metabolite profiling revealed a genotype- and tissue-specific pattern regarding the anthocyanin composition [22]. Petunidin was the major anthocyanidin compound found both in the flesh and the peel of purple potato varieties studied by Yine et al. [21]. In this study, petunidin accounted for 63–66% of the total anthocyanidin content of purple peel and flesh. The same findings were observed by Kita et al. [23] when studying purple- and red-fleshed potato cultivars, where petunidin-3-p-coumaroylrutinoside-5-glucoside was the major anthocyanin compound found in the purple-fleshed varieties Salad Blue (29.31 ± 0.73 mg∙100 g−1 dry weight (dw)), Valfi (43.11 ± 0.37 mg∙100 g−1 dw), and Blue Congo (36.32 ± 0.33 mg∙100 g−1 dw). Similarly, Nemś et al. [24] identified petunidin-2-p-coumarylrutinoside-5-glucoside as the major anthocyanin present in the cultivars Salad Blue (28.34 ± 9.30 mg∙100 g−1 dw), Valfi (57.77 ± 28.75 mg∙100 g−1 dw), and Blue Congo (75.97 ± 12.38 mg∙100 g−1 dw). On the other hand, in red-fleshed potatoes, pelargonidin acyl-glycoside derivatives appear as the main anthocyanin compounds. Kita et al. [23] found pelargonidin-3-p-coumaroylrutinoside-5-glucoside as the major anthocyanin present in red-fleshed varieties, such as Rosalinde (15.14 ± 0.12 mg∙100 g−1 dw), Herbie 26 (44.46 ± 0.23 mg∙100 g−1 dw), and Highland Burgundy Red (126.38 ± 0.71 mg∙100 g−1 dw). Yin et al. [21] carried out an acid hydrolysis of the anthocyanins, studying the composition of the aglycones (anthocyanidins), reporting pelargonidin as the main anthocyanidin present in the red-fleshed cultivar Red Cloud No. 1, with a concentration of 11.73 ± 0.16 mg∙100 g−1 fresh weight (fw), which corresponded to 82% of the total anthocyanidin content. Other anthocyanin compounds were reported in the literature for red- and purple-fleshed potatoes, including delphinidin, cyanidin, peonidin, and malvidin acyl-glycoside derivatives [21,23]. Moreover, the simulation of domestic cooking processing and gastrointestinal digestion of Solanum tuberosum L. cv Vitelotte noire extracts revealed significant antimicrobial and anti-proliferative activities against Bacillus cereus and Escherichia coli in the first case (domestic cooking processes) and colon (Caco-2 and SW48) and breast cancer (MCF7, MDA-MB-231) cell lines in the latter case (gastrointestinal digestion) [95].
Carotenoids are fat-soluble pigments that can exert antioxidant properties, and they are also present in colored-flesh potatoes. According to Kotíková et al. [25] who compared the carotenoid content of yellow-fleshed, white-fleshed, purple-fleshed, and red-fleshed potato cultivars, significant differences were observed. Interestingly, yellow potatoes showed a much higher average total carotenoid content (26.22 μg∙g−1 dw) in comparison to the red and purple-fleshed cultivars (5.69 μg∙g−1 dw), indicating that carotenoid pigments are not highly concentrated in the flesh of purple- and red-fleshed potatoes [25].
Yin et al. [21] investigated 10 colored potato cultivars from China and compared the composition and antioxidant activities of their flesh and peel. The authors found that potato peels were on average 15.34 times richer in anthocyanins than the flesh; the antioxidant activity of the peels extracts was also 5.75 times higher on average than that of the flesh extracts [21]. In the same study, the flesh extracts of cv. Purple Cloud No.1 showed the strongest antioxidant activity among all the tested varieties, along with the highest total content of anthocyanidins (43.38 mg∙100 g−1 fw), a correlation which indicates anthocyanins as a major contributor to the antioxidant activity of colored potatoes [21].
Recently, there was increasing interest by consumers and food producers in colored potato varieties, due to their attractive organoleptic features (color and taste) and health-promoting chemical composition [12]. The increasing interest of the market for colored potato is stimulating private and public breeding programs to release new specialty potato cultivars such as the red-skin and red-flesh TerraRossa and AmaRosa or the purple-skin yellow-flesh cultivar Huckleberry Gold and Peter Wilcox, marketed as “Purple Sun” or “Blue Gold”, which are also characterized by a higher content of anthocyanins, anthocyanidins, and other phenolic compounds [96]. The consumption of anthocyanin-rich food products such as purple-flesh potatoes is associated with the modification of the expression of various genes involved in the metabolism of lipids, inflammation, and energy homeostasis in liver and/or fat tissues [97,98]. Moreover, extracts from purple potato tubers may improve the differentiation of gut epithelia and its barrier function against gut epithelial inflammation through the activation of AMP-activated protein kinase (AMPK) and the increase of CDX2 gene [99]. Color-fleshed potatoes are an excellent source of bioactive compounds that are effective against human colon cancer cell lines (HCT-116 and HT-29); however, prolonged storage may affect their antiproliferative and pro-apoptotic activities [100]. Red- and purple-fleshed potato extracts were also effective against tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity through the recovery of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzyme activities [101]. Therefore, a market niche for colored potato-based food products was created, such as potato chips and crisps. However, the frying process to produce colored potato crisps can cause a 38–70% degradation of anthocyanin compounds, with pelargonidin and malvidin acyl-glycoside derivatives being more stable during the frying process in comparison to petunidin acyl-glycoside derivatives [23]. Nevertheless, despite the reduced contents of anthocyanins in processed compared to raw potatoes, colored potato crisps can present bright attractive colors, in addition to 2–3 times higher antioxidant activities and 40% higher contents of polyphenols than standard snacks made of commonly used yellow potatoes and corn [23,24]. Moreover, in a recent study, Nemś and Pęksa [94] incorporated dried red- and purple-fleshed potatoes into fried snacks and doughs, reporting a beneficial effect on the inhibition of oxidative changes in lipids compared to control material (yellow snacks), particularly when incorporating material from purple-fleshed potato varieties of Blue Congo and Valfi. These effects were attributed to the higher content of colored snacks in polyphenols and anthocyanins than control, with petunidin 2-p-coumaroyl-rutinoside-5-glucoside being the major anthocyanin present in both cultivars [94]. Other domestic cooking processes such as boiling, baking, steaming, and microwaving may also affect the anthocyanin content and antioxidant capacity of colored potatoes, with processing (steaming and microwaving) showing the best results in retaining anthocyanin content and antioxidant activity [102,103,104,105,106]. Thermal processing affects not only anthocyanins but also carotenoids which are heat-sensitive and may be degraded, isomerized, or oxidized after domestic cooking processes [25]. According to Qiu et al. [107], anthocyanin content decreased with prolonged drying time and high drying temperatures due to higher degradation rates and shorter half-life values compared to shorter drying procedures with lower temperatures. Therefore, the antioxidant properties of colored potatoes can be beneficial not only to human health but also to the shelf life of processed food products. Another important aspect of processed food products based on processed colored potatoes is that the various types of processing (French fries, chips, and puree) reduce the content of antinutritional factors such as the glykoalkaloids α-chaconine and α-solanine, thus increasing the overall nutritional quality of the semi-processed and final products [108].

2.2. Sweet Potato

Sweet potato (Ipomoea batatas (L.) Lam., Convolvulaceae) is a perennial species native to Latin America which is highly appreciated for its fleshly tuberous roots that are widely used in the food and non-food industry depending on starch content and properties [109,110]. In Japan, purple sweet-potato anthocyanins are used as ingredients in several food products and beverages [111,112]. The flesh of the roots is usually white, yellow, or orange, although several cultivars with purple-colored flesh and a high content of anthocyanins also exist [113,114]. It is the fourth most produced vegetable in the world after potato, cassava, and tomato with a total production of 113 million tons in 2017, most of which (63.8%) were produced in China [115]. The nutritional value of the edible roots consists in the richness of carbohydrates, dietary fibers, vitamins, and minerals, while several polyphenolic compounds, peptides, and carotenoids are also present in considerable amounts in the flesh [116] and peels [74] of the tubers. The high calorific value of sweet potato roots makes the species one of the most important food crops in terms of calorific contributors to the human diet [117]. Starch is the main calorific component of sweet-potato tubers with significant variation in its structural and functional properties which depend mostly on the genotype and are not correlated with flesh color [118], although, using a proteomic approach, a recent study revealed that starch degradation may contribute to anthocyanin biosynthesis and accumulation in purple sweet-potato roots [119]. Chlorogenic acid, protocatechuic acid, salicylic acid, and caffeoylquinic acid derivatives are the main phenolic acids detected in purple sweet-potato roots and are responsible for their antioxidant capacity [48,120,121], while orange-fleshed sweet-potato cultivars are rich in provitamin A and also show significant antioxidant activity [113,122,123]. Moreover, in the study of Lebot et al. [124], the antioxidant activity of sweet-potato cultivars with purple, orange, and white flesh was correlated mostly with the presence of caffeoylquinic acid derivatives and less with total anthocyanin content, whereas, according to Oki et al. [8], the contribution of phenolic compounds in radical-scavenging activity is also dependent on the genotype. In contrast, according to the study of Kubow et al. [125], anthocyanins are responsible for the antioxidant capacity of sweet-potato tubers. In the same study, it was reported that the anthocyanin species were detected in the small intestinal and the ascending colonic vessel, depending on the sweet-potato genotype, and the antioxidant activity was increased accordingly [125]. According to the report of Meng et al. [126] who studied the digestion kinetics of sweet-potato polyphenols, the maximum release was recorded 2 h after intestinal digestion and was induced by gastric acid and pepsin [126]. Moreover, acylated anthocyanins from sweet potato are considered as complex and less susceptible to intestinal degradation [127,128], while Sun et al. [129] suggested a prebiotic-like activity of anthocyanins through the modulation of microbiota in the intestine. These results highlight the importance of unraveling the bioavailability and bioaccessibility patterns influencing the antioxidant potential of purple-fleshed sweet potatoes [125].
Acylated anthocyanins are responsible for the intense color of purple-fleshed sweet potatoes [66,130], which renders them good candidates sources for natural colorants with practical application in the food industry [131]. Moreover, peels are also a good source of natural pigments since they contain significant amounts of anthocyanins, and the exploitation of this by-product for obtaining coloring agents would increase the added value of the sweet-potato crop [74]. The total anthocyanin content and compositional profile may differ among the various genotypes, with a total of 39 different anthocyanins isolated so far [132,133]. The main anthocyanins isolated from purple sweet-potato extracts were identified as cyanidin, peonidin, and pelargonidin derivatives [26,27,28,29,30,110,134,135], which were effective against alcohol-induced liver injury in rats when administrated at median doses (100 mg∙kg−1 body weight), whereas higher doses (300 mg∙kg−1 body weight) had a pro-oxidant effect and promoted liver injury [136]. Moreover, cyanidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside which was isolated from purple-fleshed sweet potatoes was shown to be effective both in vitro and in vivo in inhibiting hepatic glucose secretion and reducing blood glucose [137,138,139], while peonidin suppressed the excessive expression of the HER2 protein showing anticancer activities [140]. According to Luo et al. [141], cyanidin 3-caffeoyl-feruloyl sophoroside-5-glucoside and peonidin 3-dicaffeoyl sophoroside-5-glucoside were the most effective anthocyanins isolated from the purple sweet-potato cultivar Eshu No. 8. In another study, the oral administration of purple sweet-potato color attenuated cognitive deficits in domoic acid-treated mice through mitochondrial biogenesis signaling and the decrease of p47phox and gp91phox expression [142], while similar results were reported by Zhuang et al. [143], who suggested the regulation of AMPK/autophagy signaling as the mechanism of action. The same pigment was effective against neuroinflammation in mouse brain through the inhibition of mitogen-activated protein kinase (MAPK) and the activation of nuclear factor κB (NF-κB) [144], as well as against bladder cancer through the inhibition of the signaling of phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt or protein kinase B (PI3K/Akt) [145]. In particular, for mitochondrial biogenesis, it was reported that anthocyanins can bind and stimulate estrogen receptor-α and then increase the expression of nuclear respiratory factor-1 (NRF-1) [146]. Anthocyanin-rich extracts from purple sweet potato were moderately effective against human colon cancer cell lines (HCT-116 and HT-29) through the inhibition of tyrosine kinase activity, whereas they showed no effectiveness against the CCD-33Co cell line [67]. Moreover, Yoshimoto et al. reported that the antimutagenic activity of sweet-potato extracts was attributed mainly to cyanidin content (63% inhibition of mutagenicity of Trp-1 against Salmonella tymphimurium TA 98 at the dose of 1.5 mM) [147], while Zhao et al. suggested that anthocyanin-rich extracts from sweet potato are potent anti-aging (at the dose of 1000 mg/kg body weight), anti-hyperglycemic (at the dose of 1 g/kg body weight), and anti-tumor agents (68% tumor inhibition at the dose of 1000 mg/kg body weight) [148]. In another study, highly acylated anthocyanins showed effectiveness against hyperuricemia and kidney inflammation in allopurinol-induced hyperuricemic mice [149], while purple sweet-potato color reduced renal damage through the downregulation of vascular endothelial growth factor receptor (VEGFR2) expression [150]. The regular intake of anthocyanins is also highly associated with the prevention of various chronic liver diseases, and it can reduce lipid accumulation in liver tissues and alleviate oxidative stress and hepatic inflammation [25,102,151,152,153,154,155,156]. Other hepatoprotective effects of purple sweet potatoes include hepatic insulin resistance in high-fat diet-treated mice through the decrease of reactive oxygen species (ROS) production and the inhibition of endoplasmic reticulum (ER) liver stress (administration of purple sweet-potato color at the dose of 700 mg/kg/day) [157], through the decrease in the expression of ionized calcium-binding adapter molecule 1 (Iba1), tumor necrosis factor-α, interleukin-1β, suppressors of cytokine signaling3 (SOCS3), and galectin-3 (administration of purple sweet potato color at the dose of 500 mg/kg/day) [158], or through the inhibition of nucleotide-binding domain, leucine-rich repeat (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome activation (administration of purple sweet potato color at the dose of 700 mg/kg/day) [159]. Moreover, the combinative use of black soybean and purple sweet potato (mixtures of 2:2 for black soybean and purple sweet potato) resulted in improved insulin sensitivity in streptozotocin-induced diabetic rats through the improvement of insulin and insulin receptor substrate-1 (IRS-1) expression, the increase of superoxide dismutase (SOD) levels, and reduced pancreatic necrosis [160]. In a similar study, the mixture of Curcuma longa L. and sweet potato (at the dose of 2–5 mg/kg body weight) showed significant immunomodulating properties in murine leukemia retrovirus-infected mice [161]. The administration of purple sweet potato to obese mice fed with a high-fat diet exhibited anti-obesity effects and attenuated gain weight [162]. Other bioactive compounds of purple sweet potatoes include alkali-soluble polysaccharides which presented anti-inflammatory properties in lipopolysaccharide (LPS)-treated macrophages (RAW 264.7) through the inhibition of nitric oxide, interleukin (IL)-6, IL-1β, and tumor necrosis factor alpha (TNF-α) and the increase of IL-10 [163], as well as anti-inflammatory effects against intestinal inflammation on dextran sulfate sodium (DSS)-induced mice [164], hepatoprotective properties [165], and immunomodulatory effects [166,167,168]. Non-flavonoid compounds and kaempferol derivatives are also present in sweet-potato tuber tissues, and they contribute to the overall bioactive capacity of sweet potato [28].
Processing and storage conditions are important for the chemical composition and the visual quality of sweet-potato tubers, with heating treatments and higher pH having a detrimental effect on anthocyanins and starch content and on flesh color [139,169,170,171,172]. Pretreatments such as blanching, osmotic dehydration, ultrasound-assisted dehydration, and ultrasound-assisted osmotic dehydration before microwave drying also had an impact on total phenolic and anthocyanin content of orange- and purple-fleshed sweet-potato slices [173]. Domestic cooking processes may also affect total anthocyanin and total phenolic content, with steaming suggested as the mildest process to retain the highest amount of total anthocyanins compared to fresh samples, while, at the same time, an increase in total phenolic content was observed by Phan et al. [174]. In a similar study, steaming, roasting, and boiling were suggested as the best cooking methods for retaining total phenolic, anthocyanin, and carotenoid content, respectively, in white, yellow, orange, light-purple, and deep-purple sweet-potato tubers [10].

2.3. Carrot

Carrot (Daucus carota L. ssp. sativus Hoffm.) belongs to the Apiaceae family and is a highly appreciated vegetable consumed for its edible fleshy roots. There are two cultivar groups depending on root color, namely, the carotene or western carrot (Daucus carota ssp. sativus var. sativus) and the eastern or anthocyanin carrot (Daucus carota ssp. sativus var. atrorubens Alef.), which are widely cultivated throughout the world with an annual production of 42.8 million tons including turnips [115]. Although the orange-colored carrots are the most popular ones, a broad genetic basis exists with many other shades of root flesh (red, white, yellow, black, purple, or multi-color) which attract interest due to their nutritional value and associated health effects [175]. Recently, new genetically biofortified cultivars were developed which contain not only α- and β-carotene but also anthocyanins and lycopene [176]. In particular, for black or purple carrots, several research reports highlighted their beneficial health effects on human health, and they are widely used so far as natural sources of blue color and functional ingredients in the food industry [33,40].
Black carrots contain high amounts of mono-acylated anthocyanins which are less prone to thermal degradation, while they can retain their color at various pH values and storage conditions [31,32,34]. These functional and structural characteristics of colored carrot pigments make them good candidates for the extraction of natural colorant agents with practical applications in the food industry, especially in food products with low pH, in beverages and confectioneries [40,131,177]. However, despite their stability under various conditions, Espinosa-Acosta et al. [82] did not suggest their use in food models such as yoghurt and jelly, except for the case of ethanolic extracts of black carrots, which could be incorporated into jellies to increase the antioxidant activity of the final product. Moreover, Assous et al. [86] suggested the use of black-carrot pigments as coloring agents in hard candy and sweet jelly without significant differences in the sensorial profile compared to the control, while the same pigments protected sunflower oil from lipid peroxidation. The use of black-carrot extracts was also proposed for the preparation of jams and marmalades, where the main anthocyanins were slightly affected after gastric ingestion and storage at 4 °C [178], as well in co-pigmentation with other natural colorants (e.g., plum, jamun, strawberry, and pomegranate juices), to increase the color stability to heat treatments and pH variation [179]. On the other hand, red and yellow carrots are rich in carotenoids and lycopene and β-carotene in particular [37,38], which, according to Horvitz et al. [180], are both bioavailable and can provide a significant amount of these carotenoids to human diet.
The main anthocyanins detected are mostly cyanidin derivatives, and, according to Frond et al. [48], the most abundant anthocyanin identified in black-carrot extracts was cyanidin-3-(p-coumaroyl)-diglucoside-5-glucoside. In the study of Montilla et al. [33], the main detected anthocyanins in Daucus carota subsp. sativus var. atrorubens Alef. were identified as acylated cyanidin 3-xylosyl(glucosyl)galactosides with sinapic acid, ferulic acid, and coumaric acid, and significant differences were observed between genotypes (Antonina, Beta Sweet, Deep Purple, and Purple Haze) in terms of total and individual anthocyanin content. Similar results were reported in the earlier study of Kammerer et al. [181], with acylated and non-acylated cyanidin derivatives found in the highest amounts, while they also suggested significant differences between 15 different black-carrot cultivars, as well as between roots of the same cultivar. Moreover, in black-carrot juice, two more compounds were identified, namely, cyanidin-3-xylosyl-galactoside and cyanidin-3-xylosyl (feruloylglucosyl)galactoside [35], while Schwarz et al. [36] isolated four more pigments identified as vinylphenol and vinylguaiacol adducts of cyanidin derivatives which are formed during the storage of juice through the reaction of phenolic acids with anthocyanins. Regarding the health effects of anthocyanins, extracts from purple carrot were moderately effective against HCT-116 human colon cancer cell lines through the inhibition of tyrosine kinase activity, whereas they showed no effectiveness against HT-29 and CCD-33Co cell lines [67]. Yet, black-carrot crude extracts exhibited significant antioxidant, cytoprotective, and anti-angiogenic properties, indicating a synergistic effect of the various polyphenols (anthocyanins, phenolic acids, and flavonoids) contained in the root extracts [182]. Although non-digested purple carrot extract is more potent than the digested extract, Olejnik et al. [183] reported that gastrointestinal digested purple-carrot extract had intracellular ROS-inhibitory activity and protected colonic cells against oxidative stress by reducing oxidative DNA damage by 20.7%. According to Blando et al. [184], the anthocyanin-rich extracts from black carrots contained mostly anthocyanins acylated with cinnamic-acid derivatives, which exhibited anti-inflammatory activities through the reduction of the expression of endothelial inflammatory antigens. Apart from anthocyanins, black carrots are a good source of phenolic acids, namely, chlorogenic and caffeic acids, which contribute to the overall antioxidant capacity [48,185].
Processing may affect the chemical composition and antioxidant properties of black-carrot juice, and the use of pectinase during maceration increased the total anthocyanin content, the overall antioxidant capacity, and the juice yield of enzyme-treated compared to normally pressed juice [186,187]. The use of ultrasound and mild heating (50 °C) may increase the extraction yield of anthocyanins from black-carrot pomace, especially the content of cyanidin-3-xyloside-galactoside-glucoside-ferrulic acid and cyanidin-3-xyloside-galactoside, which were detected in the highest amounts [71]. Another processing treatment which could increase the bioavailability and stability of anthocyanins in black-carrot-based food products is the microencapsulation of anthocyanin-rich extracts [83]. Moreover, wounding stress may increase anthocyanin content, chlorogenic acid in particular, thus improving the nutritional and functional value of the obtained food products [188].

2.4. Beet Root

Beet or table beet (Beta vulgaris L.) belongs to the Amaranthaceae family and is commonly used for its edible fleshy red roots and tender leaves. Beet roots contain betalains, a class of compounds which is further divided into betacyanins and betaxanthins [39]. The composition of betalains and the ratio of betacyanins to betaxanthins depends on tyrosine production and its conversion to betalains, with significant differences observed between red and yellow beet roots [189]. The most commonly found betacyanins are betanins which are responsible for the red vivid color of beet roots, and they are water-soluble and sensitive to prolonged heating [40]. Betanins are commercially available as color additives (E162) in powder form or as juice concentrates following vacuum evaporation [39]; however, there is a great diversity in flesh color among the beet-root genotypes with variable intensities of red color or other shades ranging from white to orange. Apart from the genotype, color intensity is also affected by growing conditions and maturity stage, storage conditions, and processing treatments [88,190,191]. Beet roots with yellow color are most abundant in betaxanthins, while betacyanins are present in lesser amounts [41]. In the study of Wettasinghe et al. [192], beet-root genotypes with diverse flesh colors exhibited significant differences in antioxidant activity and in phase II enzyme induction capacity, which is associated with cancer chemoprotective effects [192]. Moreover, Lee et al. [42] reported that betanine and betaine extracted from red- and yellow-colored beet roots were effective against HepG2 cell proliferation in a dose-dependent manner. In the same study, the main identified betalains detected in the cultivar with yellow roots (Burpee’s Golden Globe) were vulgaxanthin I and betanin [42]. Vulić et al. [193] also reported that the beet-root pomace, a by-product of the beet-root juice extraction, has a high content of betalains and phenolic compounds which exhibited in vitro antiradical activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and in vivo antioxidant and hepatoprotective activity, suggesting that it could be used as an excellent nutraceutical resource or an ingredient of functional food products.

2.5. Yam

Yam includes various species of the Dioscorea genus (Dioscoreaceae), although sometimes it is confused with other root vegetables such as sweet potatoes, oca, taro, etc., which locally may be referred to as yams [194]. Tuber flesh color can be white, yellow, red, or purple depending on the cultivar, with significant differences in bioactive compound content and antioxidant properties [194,195]. Purple yam or water yam (Dioscorea alata purpurea) is usually cultivated in tropical and subtropical regions of the world, and its edible roots are very rich in starch and amylose [196], although a great variation in chemical composition of the edible parts of the species was reported [197]. Resistant starch from purple yam (D. alata) was effective against hyperlipidemia in high-fat diet-fed hamsters through the amelioration of lipid metabolism and the modulation of gut microbiota [196,198]. Moreover, extracts from roots significantly reduced blood glucose levels in Wistar rats with alloxan-induced hyperglycemia [199] or cholesterol (total and low-density lipoprotein (LDL)) and triglycerides in hypercholesterolemic rats [200], ameliorated doxorubicin (DOX)-induced cardiotoxicity [201], showed protective effects against aniline-induced spleen toxicity [202] and in vivo anti-inflammatory activities against λ-carrageenan-induced paw edema in mice [203], and could be used as an adjuvant in bone-marrow-derived dendritic cell (DC)-based vaccines for cancer therapy [204]. D. alata root extracts may also alleviate cellular fibrosis through the downregulation of the transforming growth factor-beta (TGF-β)/Smad signaling pathway and the modulation of epithelial–mesenchymal transition (EMT) expression in kidneys [205]. On the other hand, according to Chan et al. [206], root extracts are also effective against CCl4-induced liver injury and hepatic fibrosis. Other health effects include the improvement in function of large bowel and modulation of fecal microflora [207], beneficial effects in gastrointestinal function [208] and cognitive ability [209,210], and the activation of the immune system [211]. The root color of purple yam (D. alata) is attributed to the high content of anthocyanins which exhibit significant antibacterial activities [212], anti-inflammatory effects on trinitrobenzenesulfonic acid (TNBS)-induced colitis in mice [213], antiglycative properties [214], and antidiabetic properties [215,216]. The main detected anthocyanins in this species were identified as cyanidin, pelargonidin, and peonidin-type compounds and alatanins A–C [43]; however, the individual compound profile and the overall anthocyanin content are affected by maturity stage and the expression of the concomitant genes [44]. Apart from D. alata, which is considered the main purple yam, there are also cultivars of D. trifida or cush-cush yam which contain peonidin, cyanidin, and pelargonidin aglycones [45]. Other compounds with bioactive properties are also present, namely, phenolic acids such as ferulic, sinapic, vanillic, caffeic acid, and p-coumaric acid, and others, which presented immunomodulatory properties [217,218], proteins with estrogen-stimulating activities that may relieve menopausal syndrome [219], allantoin and dioscin [220], dioscorin [221], or β-sitosterol and ethyl linoleate with anti-atherosclerotic activity [222]. On the other hand, carotenoids and β-carotene in particular are responsible for the root color of yellow yam (D. cayennensis) [47]. Yam roots may contain antinutritional factors such as tannins and diosgenin, which also present bioactive properties. For example, antidyslipidemic effects were reported for diosgenin extracts from purple and yellow yams without affecting body weight gain [220,223], while diosgenin and furostanol glycosides and spirostanol glycosides were effective against the proliferation of various cancer cell lines (MCF-7, A 549, and Hep G2) [224].
A very common use of purple yam is the substitution of wheat flour for bakery products and food products in general without affecting the sensorial acceptance of the products by consumers [225,226,227], while yam flour can be used for gluten-free bakery products [228].

2.6. Onion

Onion (Allium cepa L., Alliaceae) is one of the most important species of the Allium genus, which is commonly used for its edible bulbs. There is a great number of cultivars available with a great diversity in color, which usually refers to bulb skin color, since, in most cases, the presence of pigments is limited to the outer skins of the bulb [229]. In many countries, onion bulbs are considered the main dietary source of flavonoids, a high proportion of which is attributed to the anthocyanin content [70,230]. However, most of the studies refer to red-onion cultivars which contain various polyphenols including acylated and non-acylated cyanidin glucosides, and less information is available about the profile of anthocyanins in purple onions [48,49]. The biosynthesis of anthocyanins involves the shikimate pathway and the activity of anthocyanidin synthase, which catalyzes the production of anthocyanidins, and, after further enzymatic reactions, the various anthocyanins are produced [5]. Comparing green, yellow, red, and purple onion, Benkeblia [231] observed higher total phenolic content and antioxidant properties in red and purple onion-bulb extracts. Similar results were reported by Zhang et al. [232] in a study comparing white, yellow, and red onion, with the latter showing considerably higher total anthocyanin, flavonoid, and polyphenol content, which was also correlated to high antioxidant activity measured through DPPH, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+), and fluorescence recovery after photobleaching (FRAP) assays. Bulb extracts are potent bioactive natural matrices, and, according to the study of Oboh et al. [233], extracts of purple onion were effective against angiotensin-converting enzyme, α-amylase, and α-glucosidase activity, showing significant antidiabetic and anti-hypertensive effects. Moreover, skins of pearl onion exhibited significant anti-inflammatory properties and inhibitory effects against radical-induced DNA scission [234]. In terms of antioxidant activity, purple onions exhibited higher oxygen radical absorbance capacity (ORAC) values than white onions, which indicates a higher concentration of bioactive compounds [235]. A preliminary study conducted by Khiari et al. [236] suggested that, depending on the quality of the plant residues, onion solid waste, also constituted primarily by the outer dry layers of the bulbs, may be used to extract polyphenols with potential antioxidant activity, and the yield of total polyphenols can be optimized using ethanol extracts, with extraction time up to 6 h, while maintaining relatively low extraction temperature (40 °C gave better results than 60 °C).

2.7. Other Root Vegetables

Radish (Raphanus sativus L., Brassicaceae) is a cruciferous species, well known for its normally white edible fleshy hypocotyls which come in different shapes, sizes, and skin colors. Apart from white-fleshed cultivars, there are also genotypes with pink and purple hypocotyls due to the presence of pigments in the xylem [50]. Pigmentation may also change with the hypocotyl development stage [237]. Purple color implies the presence of anthocyanins, and, according to the study of Reference [51], 60 different compounds were detected and identified as cyanidin glucosides. Most of the anthocyanins are present in acylated forms of cyanidin glucosides which increase their stability, and they could be easily used as natural colorants in functional foods [7,50,238,239], while root extracts may also exhibit beneficial health effects against gastric injuries [240].
Purple kohlrabi (Brassica oleracea var. gongylodes) is another species of the Brassicaceae family with intense purple color, whose edible part is the swollen fleshy meristem. The pigments are located in the meristem skin and consist of cyanidin and cyanidin glucosides which are responsible for the strong antioxidant properties of the species [54,55,56,57]. Examining the antioxidant activity of kohlrabi ethanol and water extracts, Pak et al. [241] observed strong DPPH radical-scavenging activity, and purple kohlrabi extracts had higher antioxidant capacity compared to green kohlrabi extracts. Similarly, comparing green and red kohlrabi, Jung et al. [242] observed that the latter had double the total phenolic content, as well as a higher antioxidant (DPPH, ABTS, and peroxynitrite scavenging activity assay (ONOO−)) effect compared to green kohlrabi. In the same study, red kohlrabi methanol extract had stronger anti-inflammatory, antidiabetic, and antioxidant effects than the green kohlrabi methanol extract.
Taro (Colocasia esculenta L.) is a root vegetable of the Araceae family with great genetic diversity in plant morphology, including the color of corm flesh, which can be white, purple, brown, or blackish [57,243,244]. The main detected anthocyanins were identified as cyanidin and pelargonidin glucosides, and they exhibit significant antioxidant and anti-inflammatory activities [58].

3. Conclusions

Root vegetables with intense and uncommon colors are very important in the human diet, not only because they increase the overall intake of health-promoting compounds, but also because they diversify the daily diet in terms of color, flavor, and chemical composition, which imparts distinct functional effects on the human body. The inclusion of such root vegetables either raw in fresh salads or in cooked dishes may increase palatability and appeal for healthier food products, although proper marketing is always an issue since consumers are usually reluctant to introduce new flavors and unconventional products that break the mold. Nevertheless, the current trends in the food and beverage market and the increased public demand for substituting synthetic compounds with natural alternatives could boost the establishment of these species and help the crossing over from niche products to widely accepted ones with diverse uses in the food industry. Further research is also needed in order to (i) identify those correlations and mechanisms of action responsible for the antioxidant properties and health effects of the pigmented vegetables, (ii) evaluate agronomic practices that will increase the bioactive capacity of the final products through the improved pigmentation, (iii) study post-harvest and processing treatments that will make these compounds less prone to degradation and easier to use in the design of functional foods and as natural coloring agents, and (iv) define efficient extraction protocols that will allow high yields and high stability and quality of coloring agents extracted from plant sources. Finally, increasing the knowledge about the chemical composition and the health effects of individual compounds of colored root vegetables could be further exploited through breeding programs for the production of elite genotypes with increased content of coloring compounds and tailor-made health effects, as well as through plant in vitro strategies for the production of specific natural secondary metabolites and further use in the pharmaceutical and the food and beverage industries.

Author Contributions

All authors contributed equally to the writing of the original draft and final draft preparation.

Funding

This work was supported by the USDA National Institute of Food and Agriculture and Hatch Appropriations under Project #PEN04723 and Accession #1020664; The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Program PT2020 for financial support to CIMO (UID/AGR/00690/2019), to FEDER-Interreg España-Portugal programme for financial support through the project 0377_Iberphenol_6_E and TRANSCoLAB 0612_TRANS_CO_LAB_2_P, and to the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of project Mobilizador Norte-01-0247-FEDER-024479: Valor Natural®.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Sasaki, N.; Nishizaki, Y.; Ozeki, Y.; Miyahara, T. The role of acyl-glucose in anthocyanin modifications. Molecules 2014, 19, 18747–18766. [Google Scholar] [CrossRef] [PubMed]
  2. Kyriacou, M.C.; Rouphael, Y. Towards a new definition of quality for fresh fruits and vegetables. Sci. Hortic. (Amst.) 2018, 234, 463–469. [Google Scholar] [CrossRef]
  3. Chaves-Silva, S.; dos Santos, A.L.; Chalfun-Júnior, A.; Zhao, J.; Peres, L.E.P.; Benedito, V.A. Understanding the genetic regulation of anthocyanin biosynthesis in plants—Tools for breeding purple varieties of fruits and vegetables. Phytochemistry 2018, 153, 11–27. [Google Scholar] [CrossRef] [PubMed]
  4. Menzies, I.J.; Youard, L.W.; Lord, J.M.; Carpenter, K.L.; van Klink, J.W.; Perry, N.B.; Schaefer, H.M.; Gould, K.S. Leaf colour polymorphisms: A balance between plant defence and photosynthesis. J. Ecol. 2016, 104, 104–113. [Google Scholar] [CrossRef]
  5. Khandagale, K.; Gawande, S. Genetics of bulb colour variation and flavonoids in onion. J. Hortic. Sci. Biotechnol. 2019, 94, 522–532. [Google Scholar] [CrossRef]
  6. Wrolstad, R.E.; Culver, C.A. Alternatives to Those Artificial FD&C Food Colorants. Annu. Rev. Food Sci. Technol. 2012, 3, 59–77. [Google Scholar]
  7. Giusti, M.M.; Wrolstad, R.E. Acylated anthocyanins from edible sources and their applications in food systems. Biochem. Eng. J. 2003, 14, 217–225. [Google Scholar] [CrossRef]
  8. Oki, T.; Masuda, M.; Furuta, S.; Nishiba, Y.; Terahara, N.; Suda, I. Involvement of anthocyanins and other phenolic compounds in radical-scavenging activity of purple-fleshed sweet potato cultivars. J. Food Sci. 2002, 67, 1752–1756. [Google Scholar] [CrossRef]
  9. Newsome, A.G.; Culver, C.A.; Van Breemen, R.B. Nature’s palette: The search for natural blue colorants. J. Agric. Food Chem. 2014, 62, 6498–6511. [Google Scholar] [CrossRef]
  10. Tang, Y.; Cai, W.; Xu, B. Profiles of phenolics, carotenoids and antioxidative capacities of thermal processed white, yellow, orange and purple sweet potatoes grown in Guilin, China. Food Sci. Hum. Wellness 2015, 4, 123–132. [Google Scholar] [CrossRef] [Green Version]
  11. Singh, B.K.; Koley, T.K.; Maurya, A.; Singh, P.M.; Singh, B. Phytochemical and antioxidative potential of orange, red, yellow, rainbow and black coloured tropical carrots (Daucus carota subsp. sativus Schubl. & Martens). Physiol. Mol. Biol. Plants 2018, 24, 899–907. [Google Scholar] [PubMed]
  12. Rytel, E.; Tajner-czopek, A.; Kita, A.; Aniołowska, M.; Kucharska, A.Z.; Hamouz, K. Content of polyphenols in coloured and yellow fleshed potatoes during dices processing. Food Chem. 2014, 161, 224–229. [Google Scholar] [CrossRef] [PubMed]
  13. Khan, M.I.; Giridhar, P. Plant betalains: Chemistry and biochemistry. Phytochemistry 2015, 117, 267–295. [Google Scholar] [CrossRef] [PubMed]
  14. Khoo, H.E.; Azlan, A.; Tang, S.T.; Lim, S.M. Anthocyanidins and anthocyanins: Colored pigments as food, pharmaceutical ingredients, and the potential health benefits. Food Nutr. Res. 2017, 61, 1361779. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  15. Merhan, O. The Biochemistry and Antioxidant Properties of Carotenoids. In Carotenoids; Cvetkovic, D., Nikolic, G., Eds.; IntechOpen: London, UK, 2016; pp. 51–66. [Google Scholar]
  16. Young, A.J.; Lowe, G.L. Carotenoids—Antioxidant properties. Antioxidants 2018, 7, 28. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  17. Indra, V.K. Phytochemicals in Plant Cell Cultures; Vasil, I.K., Ed.; Elsevier: Amsterdam, The Netherlands, 1988. [Google Scholar]
  18. Rahimi, P.; Abedimanesh, S.; Mesbah-Namin, S.A.; Ostadrahimi, A. Betalains, the nature-inspired pigments, in health and diseases. Crit. Rev. Food Sci. Nutr. 2019, 59, 2949–2978. [Google Scholar] [CrossRef]
  19. Miguel, M.G. Betalains in some species of the amaranthaceae family: A review. Antioxidants 2018, 7, 53. [Google Scholar] [CrossRef] [Green Version]
  20. Belhadj Slimen, I.; Najar, T.; Abderrabba, M. Chemical and antioxidant properties of betalains. J. Agric. Food Chem. 2017, 65, 675–689. [Google Scholar] [CrossRef]
  21. Yin, L.; Chen, T.; Li, Y.; Fu, S.; Li, L.; Xu, M.; Niu, Y. A comparative study on total anthocyanin content, composition of anthocyanidin, total phenolic content and antioxidant activity of pigmented potato peel and flesh. Food Sci. Technol. Res. 2016, 22, 219–226. [Google Scholar] [CrossRef] [Green Version]
  22. Oertel, A.; Matros, A.; Hartmann, A.; Arapitsas, P.; Dehmer, K.J.; Martens, S.; Mock, H.P. Metabolite profiling of red and blue potatoes revealed cultivar and tissue specific patterns for anthocyanins and other polyphenols. Planta 2017, 246, 281–297. [Google Scholar] [CrossRef]
  23. Kita, A.; Bąkowska-Barczak, A.; Hamouz, K.; Kułakowska, K.; Lisińska, G. The effect of frying on anthocyanin stability and antioxidant activity of crisps from red- and purple-fleshed potatoes (Solanum tuberosum L.). J. Food Compos. Anal. 2013, 32, 169–175. [Google Scholar] [CrossRef]
  24. Nemś, A.; Pęksa, A.; Kucharska, A.Z.; Sokół-ŁĘtowska, A.; Kita, A.; Drozdz, W.; Hamouz, K. Anthocyanin and antioxidant activity of snacks with coloured potato. Food Chem. 2015, 172, 175–182. [Google Scholar] [CrossRef] [PubMed]
  25. Kotíková, Z.; Šulc, M.; Lachman, J.; Pivec, V.; Orsák, M.; Hamouz, K. Carotenoid profile and retention in yellow-, purple- and red-fleshed potatoes after thermal processing. Food Chem. 2016, 197, 992–1001. [Google Scholar] [CrossRef] [PubMed]
  26. Ge, J.; Hu, Y.; Wang, H.; Huang, Y.; Zhang, P.; Liao, Z.; Chen, M. Profiling of anthocyanins in transgenic purple-fleshed sweet potatoes by HPLC-MS/MS. J. Sci. Food Agric. 2017, 97, 4995–5003. [Google Scholar] [CrossRef] [PubMed]
  27. Hu, Y.; Deng, L.; Chen, J.; Zhou, S.; Liu, S.; Fu, Y.; Yang, C.; Liao, Z.; Chen, M. An analytical pipeline to compare and characterise the anthocyanin antioxidant activities of purple sweet potato cultivars. Food Chem. 2016, 194, 46–54. [Google Scholar] [CrossRef]
  28. Pacheco, M.T.; Escribano-Bailón, M.T.; Moreno, F.J.; Villamiel, M.; Dueñas, M. Determination by HPLC-DAD-ESI/MSn of phenolic compounds in Andean tubers grown in Ecuador. J. Food Compos. Anal. 2019, 84, 103258. [Google Scholar] [CrossRef]
  29. Wang, A.; Li, R.; Ren, L.; Gao, X.; Zhang, Y.; Ma, Z.; Ma, D.; Luo, Y. A comparative metabolomics study of flavonoids in sweet potato with different flesh colors (Ipomoea batatas (L.) Lam). Food Chem. 2018, 260, 124–134. [Google Scholar] [CrossRef]
  30. Zhang, J.L.; Luo, C.L.; Zhou, Q.; Zhang, Z.C. Isolation and identification of two major acylated anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) by UPLC-QTOF-MS/MS and NMR. Int. J. Food Sci. Technol. 2018, 53, 1932–1941. [Google Scholar] [CrossRef]
  31. Gizir, A.M.; Turker, N.; Artuvan, E. Pressurized acidified water extraction of black carrot [Daucus carota ssp. sativus var. atrorubens Alef.] anthocyanins. Eur. Food Res. Technol. 2008, 226, 363–370. [Google Scholar] [CrossRef]
  32. Kirca, A.; Özkan, M.; Cemeroǧlu, B. Effects of temperature, solid content and pH on the stability of black carrot anthocyanins. Food Chem. 2007, 101, 212–218. [Google Scholar] [CrossRef]
  33. Türker, N.; Erdoğdu, F. Effects of pH and temperature of extraction medium on effective diffusion coefficient of anthocynanin pigments of black carrot (Daucus carota var. L.). J. Food Eng. 2006, 76, 579–583. [Google Scholar] [CrossRef]
  34. Montilla, E.C.; Arzaba, M.R.; Hillebrand, S.; Winterhalter, P. Anthocyanin composition of black carrot (Daucus carota ssp. sativus var. atrorubens Alef.) cultivars antonina, beta sweet, deep purple, and purple haze. J. Agric. Food Chem. 2011, 59, 3385–3390. [Google Scholar] [CrossRef] [PubMed]
  35. Garcia-Herrera, P.; Pérez-Rodríguez, M.L.; Aguilera-Delgado, T.; Labari-Reyes, M.J.; Olmedilla-Alonso, B.; Camara, M.; de Pascual-Teresa, S. Anthocyanin profile of red fruits and black carrot juices, purees and concentrates by HPLC-DAD-ESI/MS-QTOF. Int. J. Food Sci. Technol. 2016, 51, 2290–2300. [Google Scholar] [CrossRef]
  36. Schwarz, M.; Wray, V.; Winterhalter, P. Isolation and identification of novel pyranoanthocyanins from black carrot (Daucus carota L.) juice. J. Agric. Food Chem. 2004, 52, 5095–5101. [Google Scholar] [CrossRef] [PubMed]
  37. Kaur, A.; Sogi, D.S. Effect of osmotic dehydration on physico-chemical properties and pigment content of carrot (Daucus carota L.) during preserve manufacture. J. Food Process. Preserv. 2017, 41, e13153. [Google Scholar] [CrossRef]
  38. Mayer-Miebach, E.; Behsnilian, D.; Regier, M.; Schuchmann, H.P. Thermal processing of carrots: Lycopene stability and isomerisation with regard to antioxidant potential. Food Res. Int. 2005, 38, 1103–1108. [Google Scholar] [CrossRef]
  39. Nemzer, B.; Pietrzkowski, Z.; Spórna, A.; Stalica, P.; Thresher, W.; Michałowski, T.; Wybraniec, S. Betalainic and nutritional profiles of pigment-enriched red beet root (Beta vulgaris L.) dried extracts. Food Chem. 2011, 127, 42–53. [Google Scholar] [CrossRef]
  40. Downham, A.; Collins, P. Colouring our foods in the last and next millennium. Int. J. Food Sci. Technol. 2000, 35, 5–22. [Google Scholar] [CrossRef]
  41. Moreno, D.A.; García-Viguera, C.; Gil, J.I.; Gil-Izquierdo, A. Betalains in the era of global agri-food science, technology and nutritional health. Phytochem. Rev. 2008, 7, 261–280. [Google Scholar] [CrossRef]
  42. Lee, E.J.; An, D.; Nguyen, C.T.T.; Patil, B.S.; Kim, J.; Yoo, K.S. Betalain and betaine composition of greenhouse- or field-produced beetroot (Beta vulgaris L.) and inhibition of HepG2 cell proliferation. J. Agric. Food Chem. 2014, 62, 1324–1331. [Google Scholar] [CrossRef]
  43. Moriya, C.; Hosoya, T.; Agawa, S.; Sugiyama, Y.; Kozone, I.; Shin-Ya, K.; Terahara, N.; Kumazawa, S. New acylated anthocyanins from purple yam and their antioxidant activity. Biosci. Biotechnol. Biochem. 2015, 79, 1484–1492. [Google Scholar] [CrossRef] [PubMed]
  44. Yin, J.M.; Yan, R.X.; Zhang, P.T.; Han, X.Y.; Wang, L. Anthocyanin accumulation rate and the biosynthesis related gene expression in Dioscorea alata. Biol. Plant. 2015, 59, 325–330. [Google Scholar] [CrossRef]
  45. Ramos-Escudero, F.; Santos-Buelga, C.; Pérez-Alonso, J.J.; Yáñez, J.A.; Dueñas, M. HPLC-DAD-ESI/MS identification of anthocyanins in Dioscorea trifida L. yam tubers (purple sachapapa). Eur. Food Res. Technol. 2010, 230, 745–752. [Google Scholar] [CrossRef]
  46. Fang, Z.; Wu, D.; Yü, D.; Ye, X.; Liu, D.; Chen, J. Phenolic compounds in Chinese purple yam and changes during vacuum frying. Food Chem. 2011, 128, 943–948. [Google Scholar] [CrossRef]
  47. Price, E.J.; Bhattacharjee, R.; Lopez-Montes, A.; Fraser, P.D. Carotenoid profiling of yams: Clarity, comparisons and diversity. Food Chem. 2018, 259, 130–138. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  48. Frond, A.D.; Iuhas, C.I.; Stirbu, I.; Leopold, L.; Socaci, S.; Andreea, S.; Ayvaz, H.; Andreea, S.; Mihai, S.; Diaconeasa, Z.; et al. Phytochemical characterization of five edible purple-reddish vegetables: Anthocyanins, flavonoids, and phenolic acid derivatives. Molecules 2019, 24, 1536. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  49. Liang, T.; Sun, G.; Cao, L.; Li, J.; Wang, L. Rheological behavior of film-forming solutions and film properties from Artemisia sphaerocephala Krasch. gum and purple onion peel extract. Food Hydrocoll. 2018, 82, 124–134. [Google Scholar] [CrossRef]
  50. Koley, T.K.; Khan, Z.; Oulkar, D.; Singh, B.K.; Maurya, A.; Singh, B.; Banerjee, K. High resolution LC-MS characterization of phenolic compounds and the evaluation of antioxidant properties of a tropical purple radish genotype. Arab. J. Chem. 2017. [Google Scholar] [CrossRef]
  51. Lin, L.Z.; Sun, J.; Chen, P.; Harnly, J.A. LC-PDA-ESI/MSn identification of new anthocyanins in purple bordeaux radish (Raphanus sativus L. Variety). J. Agric. Food Chem. 2011, 59, 6616–6627. [Google Scholar] [CrossRef]
  52. Park, N.I.; Xu, H.; Li, X.; Jang, I.H.; Park, S.; Ahn, G.H.; Lim, Y.P.; Kim, S.J.; Park, S.U. Anthocyanin accumulation and expression of anthocyanin biosynthetic genes in radish (Raphanus sativus L.). J. Agric. Food Chem. 2011, 59, 6034–6039. [Google Scholar] [CrossRef]
  53. Tatsuzawa, F.; Toki, K.; Saito, N.; Shinoda, K.; Shigihara, A.; Honda, T. Anthocyanin occurrence in the root peels, petioles and flowers of red radish (Raphanus sativus L.). Dye. Pigment. 2008, 79, 83–88. [Google Scholar] [CrossRef]
  54. Park, C.H.; Yeo, H.J.; Kim, N.S.; Eun, P.Y.; Kim, S.-J.; Arasu, M.V.; Al-Dhabi, N.A.; Park, S.-Y.; Kim, J.K.; Park, S.U. Metabolic profiling of pale green and purple kohlrabi (Brassica oleracea var. gongylodes). Appl. Biol. Chem. 2017, 60, 249–257. [Google Scholar] [CrossRef]
  55. Zhang, Y.; Hu, Z.; Zhu, M.; Zhu, Z.; Wang, Z.; Tian, S.; Chen, G. Anthocyanin Accumulation and Molecular Analysis of Correlated Genes in Purple Kohlrabi (Brassica oleracea var. gongylodes L.). J. Agric. Food Chem. 2015, 63, 4160–4169. [Google Scholar] [CrossRef] [PubMed]
  56. Park, W.T.; Kim, J.K.; Park, S.; Lee, S.W.; Li, X.; Kim, Y.B.; Uddin, M.R.; Park, N.I.; Kim, S.J.; Park, S.U. Metabolic profiling of glucosinolates, anthocyanins, carotenoids, and other secondary metabolites in kohlrabi (Brassica oleracea var. gongylodes). J. Agric. Food Chem. 2012, 60, 8111–8116. [Google Scholar] [CrossRef] [PubMed]
  57. Rahim, M.A.; Robin, A.H.K.; Natarajan, S.; Jung, H.J.; Lee, J.; Kim, H.R.; Kim, H.T.; Park, J.I.; Nou, I.S. Identification and characterization of anthocyanin biosynthesis-related genes in kohlrabi. Appl. Biochem. Biotechnol. 2018, 184, 1120–1141. [Google Scholar] [CrossRef] [PubMed]
  58. Kaushal, P.; Kumar, V.; Sharma, H.K. Utilization of taro (Colocasia esculenta): A review. J. Food Sci. Technol. 2015, 52, 27–40. [Google Scholar] [CrossRef]
  59. Ziarani, M.G.; Moradi, R.; Lashgari, N.; Kruger, H.G. Metal-Free Synthetic Organic Dyes; Elsevier: London, UK, 2018; ISBN 978-0-12-815647-6. [Google Scholar]
  60. Pires, T.C.S.P.; Barros, L.; Santos-Buelga, C.; Ferreira, I.C.F.R. Edible flowers: Emerging components in the diet. Trends Food Sci. Technol. 2019, 93, 244–258. [Google Scholar] [CrossRef]
  61. Amchova, P.; Kotolova, H.; Ruda-Kucerova, J. Health safety issues of synthetic food colorants. Regul. Toxicol. Pharmacol. 2015, 73, 914–922. [Google Scholar] [CrossRef]
  62. El-Wahab, H.M.F.A.; Moram, G.S.E.D. Toxic effects of some synthetic food colorants and/or flavor additives on male rats. Toxicol. Ind. Health 2013, 29, 224–232. [Google Scholar] [CrossRef]
  63. Rohrig, B. The chemistry of food coloring: Eating with your eyes. ChemMatters 2015, 2015, 5–7. [Google Scholar]
  64. Martins, N.; Roriz, C.L.; Morales, P.; Barros, L.; Ferreira, I.C.F.R. Food colorants: Challenges, opportunities and current desires of agro-industries to ensure consumer expectations and regulatory practices. Trends Food Sci. Technol. 2016, 52, 1–15. [Google Scholar] [CrossRef] [Green Version]
  65. De Pascual-Teresa, S.; Moreno, D.A.; García-Viguera, C. Flavanols and anthocyanins in cardiovascular health: A review of current evidence. Int. J. Mol. Sci. 2010, 11, 1679–1703. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  66. Horbowicz, M.; Grzesiuk, A.; DĘBski, H.; Kosson, R. Anthocyanins of fruits and vegetables - Their occurrence, analysis and role in human. Veg. Crop. Res. Bull. 2008, 68, 5–22. [Google Scholar] [CrossRef]
  67. Mazewski, C.; Liang, K.; Gonzalez de Mejia, E. Comparison of the effect of chemical composition of anthocyanin-rich plant extracts on colon cancer cell proliferation and their potential mechanism of action using in vitro, in silico, and biochemical assays. Food Chem. 2018, 242, 378–388. [Google Scholar] [CrossRef]
  68. Sestari, I.; Zsögön, A.; Rehder, G.G.; de Lira Teixeira, L.; Hassimotto, N.M.A.; Purgatto, E.; Benedito, V.A.; Peres, L.E.P. Near-isogenic lines enhancing ascorbic acid, anthocyanin and carotenoid content in tomato (Solanum lycopersicum L. cv Micro-Tom) as a tool to produce nutrient-rich fruits. Sci. Hortic. (Amst.) 2014, 175, 111–120. [Google Scholar] [CrossRef]
  69. Pérez-Gregorio, M.R.; García-Falcón, M.S.; Simal-Gándara, J. Flavonoids changes in fresh-cut onions during storage in different packaging systems. Food Chem. 2011, 124, 652–658. [Google Scholar] [CrossRef]
  70. Pérez-Gregorio, M.R.; Regueiro, J.; Simal-Gándara, J.; Rodrigues, A.S.; Almeida, D.P.F. Increasing the added-value of onions as a source of antioxidant flavonoids: A Critical Review. Crit. Rev. Food Sci. Nutr. 2014, 54, 1050–1062. [Google Scholar] [CrossRef]
  71. Agcam, E.; Akyıldız, A.; Balasubramaniam, V.M. Optimization of anthocyanins extraction from black carrot pomace with thermosonication. Food Chem. 2017, 237, 461–470. [Google Scholar] [CrossRef]
  72. McGill, A.E.J. The potential effects of demands for natural and safe foods on global food security. Trends Food Sci. Technol. 2009, 20, 402–406. [Google Scholar] [CrossRef]
  73. Yusuf, M.; Shabbir, M.; Mohammad, F. Natural colorants: historical, processing and sustainable prospects. Nat. Prod. Bioprospect. 2017, 7, 123–145. [Google Scholar] [CrossRef] [Green Version]
  74. Dusuki, N.J.S.; Abu Bakar, M.F.; Abu Bakar, F.I.; Ismail, N.A.; Azman, M.I. Proximate composition and antioxidant potential of selected tubers peel. Food Res. 2019, 4, 121–126. [Google Scholar] [CrossRef]
  75. Yahia, E.M.; Barrera, A. Antioxidant capacity and correlation with phenolic compounds and carotenoids in 40 horticultural commodities. Acta Hortic. 2010, 877, 1215–1220. [Google Scholar] [CrossRef]
  76. Hamouz, K.; Lachman, J.; Pazderů, K.; Tomášek, J.; Hejtmánková, K.; Pivec, V. Differences in anthocyanin content and antioxidant activity of potato tubers with different flesh colour. Plant Soil Environ. 2011, 57, 478–485. [Google Scholar] [CrossRef] [Green Version]
  77. Sass-Kiss, A.; Kiss, J.; Milotay, P.; Kerek, M.M.; Toth-Markus, M. Differences in anthocyanin and carotenoid content of fruits and vegetables. Food Res. Int. 2005, 38, 1023–1029. [Google Scholar] [CrossRef]
  78. Oliveira, H.; Roma-Rodrigues, C.; Santos, A.; Veigas, B.; Brás, N.; Faria, A.; Calhau, C.; de Freitas, V.; Baptista, P.V.; Mateus, N.; et al. GLUT1 and GLUT3 involvement in anthocyanin gastric transport-Nanobased targeted approach. Sci. Rep. 2019, 9, 789. [Google Scholar] [CrossRef]
  79. Reyes, L.E.; Miller, J.C.J.; Cisneros-Zevallos, L. Environmental conditions influence the content and yield of anthocyanins and total phenolics in purple- and red-flesh potatoes during tuber development. Am. J. Potato Res. 2004, 81, 187–193. [Google Scholar] [CrossRef]
  80. Gu, K.D.; Wang, C.K.; Hu, D.G.; Hao, Y.J. How do anthocyanins paint our horticultural products? Sci. Hortic. (Amst.) 2019, 249, 257–262. [Google Scholar] [CrossRef]
  81. Leong, S.Y.; Oey, I. Effects of processing on anthocyanins, carotenoids and vitamin C in summer fruits and vegetables. Food Chem. 2012, 133, 1577–1587. [Google Scholar] [CrossRef]
  82. Espinosa-Acosta, G.; Ramos-Jacques, A.L.; Molina, G.A.; Maya-Cornejo, J.; Esparza, R.; Hernandez-Martinez, A.R.; Sánchez-González, I.; Estevez, M. Stability analysis of anthocyanins using alcoholic extracts from black carrot (Daucus carota ssp. Sativus var. Atrorubens Alef.). Molecules 2018, 23, 2744. [Google Scholar]
  83. Ersus, S.; Yurdagel, U. Microencapsulation of anthocyanin pigments of black carrot (Daucus carota L.) by spray drier. J. Food Eng. 2007, 80, 805–812. [Google Scholar] [CrossRef]
  84. Braga, A.R.C.; Murador, D.C.; de Souza Mesquita, L.M.; de Rosso, V.V. Bioavailability of anthocyanins: Gaps in knowledge, challenges and future research. J. Food Compos. Anal. 2018, 68, 31–40. [Google Scholar] [CrossRef]
  85. Takahata, Y.; Kai, Y.; Tanaka, M.; Nakayama, H.; Yoshinaga, M. Enlargement of the variances in amount and composition of anthocyanin pigments in sweetpotato storage roots and their effect on the differences in DPPH radical-scavenging activity. Sci. Hortic. (Amst.) 2011, 127, 469–474. [Google Scholar] [CrossRef]
  86. Assous, M.T.M.; Abdel-Hady, M.M.; Medany, G.M. Evaluation of red pigment extracted from purple carrots and its utilization as antioxidant and natural food colorants. Ann. Agric. Sci. 2014, 59, 1–7. [Google Scholar] [CrossRef] [Green Version]
  87. Chhikara, N.; Kushwaha, K.; Sharma, P.; Gat, Y.; Panghal, A. Bioactive compounds of beetroot and utilization in food processing industry: A critical review. Food Chem. 2019, 272, 192–200. [Google Scholar] [CrossRef]
  88. Stintzing, F.C.; Carle, R. Betalains-emerging prospects for food scientists. Trends Food Sci. Technol. 2007, 18, 514–525. [Google Scholar] [CrossRef]
  89. Stokstad, E. The new potato. Science 2019, 363, 574–577. [Google Scholar] [CrossRef]
  90. Tsang, C.; Smail, N.F.; Almoosawi, S.; McDougall, G.J.M.; Al-Dujaili, E.A.S. Antioxidant Rich Potato Improves Arterial Stiffness in Healthy Adults. Plant Foods Hum. Nutr. 2018, 73, 203–208. [Google Scholar] [CrossRef] [Green Version]
  91. Tian, J.; Chen, J.; Ye, X.; Chen, S. Health benefits of the potato affected by domestic cooking: A review. Food Chem. 2016, 202, 165–175. [Google Scholar] [CrossRef]
  92. Camire, M.E.; Kubow, S.; Donelly, D.J. Potatoes and human health. Crit. Rev. Food Sci. Nutr. 2009, 49, 823–840. [Google Scholar] [CrossRef]
  93. Burlingame, B.; Mouillé, B.; Charrondière, R. Nutrients, bioactive non-nutrients and anti-nutrients in potatoes. J. Food Compos. Anal. 2009, 22, 494–502. [Google Scholar] [CrossRef]
  94. Nemś, A.; Pęksa, A. Polyphenols of coloured-flesh potatoes as native antioxidants in stored fried snacks. LWT Food Sci. Technol. 2018, 97, 597–602. [Google Scholar] [CrossRef]
  95. Ombra, M.N.; Fratianni, F.; Granese, T.; Cardinale, F.; Cozzolino, A.; Nazzaro, F. In vitro antioxidant, antimicrobial and anti-proliferative activities of purple potato extracts (Solanum tuberosum cv Vitelotte noire) following simulated gastro-intestinal digestion. Nat. Prod. Res. 2015, 29, 1087–1091. [Google Scholar] [CrossRef] [PubMed]
  96. Shock, C.C.; Brown, C.R.; Sathuvalli, V.; Charlton, B.A.; Yilma, S.; Hane, D.C.; Quick, R.; Rykbost, K.A. TerraRossa: A mid-season specialty potato with red flesh and skin and resistance to common scab and golden cyst nematode. Am. J. Potato Res. 2018, 95, 597–605. [Google Scholar] [CrossRef]
  97. Ayoub, H.M.; McDonald, M.R.; Sullivan, J.A.; Tsao, R.; Meckling, K.A. Proteomic profiles of adipose and liver tissues from an animal model of metabolic syndrome fed purple vegetables. Nutrients 2018, 10, 456. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  98. Ayoub, H.M.; McDonald, M.R.; Sullivan, J.A.; Tsao, R.; Platt, M.; Simpson, J.; Meckling, K.A. The effect of anthocyanin-rich purple vegetable diets on metabolic syndrome in obese zucker rats. J. Med. Food 2017, 20, 1240–1249. [Google Scholar] [CrossRef]
  99. Sun, X.; Du, M.; Navarre, D.A.; Zhu, M.J. Purple potato extract promotes intestinal epithelial differentiation and barrier function by activating AMP-activated protein kinase. Mol. Nutr. Food Res. 2018, 62, 1700536. [Google Scholar] [CrossRef]
  100. Madiwale, G.P.; Reddivari, L.; Holm, D.G.; Vanamala, J. Storage elevates phenolic content and antioxidant activity but suppresses antiproliferative and pro-apoptotic properties of colored-flesh potatoes against human colon cancer cell lines. J. Agric. Food Chem. 2011, 59, 8155–8166. [Google Scholar] [CrossRef]
  101. Kim, D.H.; Kim, M.; Oh, S.B.; Lee, K.M.; Kim, S.M.; Nho, C.W.; Yoon, W.B.; Kang, K.; Pan, C.H. The Protective Effect of Antioxidant Enriched Fractions from Colored Potatoes Against Hepatotoxic Oxidative Stress in Cultured Hepatocytes and Mice. J. Food Biochem. 2017, 41, e12315. [Google Scholar] [CrossRef] [Green Version]
  102. Tian, J.; Chen, J.; Lv, F.; Chen, S.; Chen, J.; Liu, D.; Ye, X. Domestic cooking methods affect the phytochemical composition and antioxidant activity of purple-fleshed potatoes. Food Chem. 2016, 197, 1264–1270. [Google Scholar] [CrossRef]
  103. Tierno, R.; Hornero-Méndez, D.; Gallardo-Guerrero, L.; López-Pardo, R.; de Galarreta, J.I.R. Effect of boiling on the total phenolic, anthocyanin and carotenoid concentrations of potato tubers from selected cultivars and introgressed breeding lines from native potato species. J. Food Compos. Anal. 2015, 41, 58–65. [Google Scholar] [CrossRef] [Green Version]
  104. Lachman, J.; Hamouz, K.; Orsák, M.; Pivec, V.; Hejtmánková, K.; Pazderů, K.; Dvořák, P.; Čepl, J. Impact of selected factors-Cultivar, storage, cooking and baking on the content of anthocyanins in coloured-flesh potatoes. Food Chem. 2012, 133, 1107–1116. [Google Scholar] [CrossRef]
  105. Bellumori, M.; Innocenti, M.; Michelozzi, M.; Cerretani, L.; Mulinacci, N. Coloured-fleshed potatoes after boiling: Promising sources of known antioxidant compounds. J. Food Compos. Anal. 2017, 59, 1–7. [Google Scholar] [CrossRef] [Green Version]
  106. Perla, V.; Holm, D.G.; Jayanty, S.S. Effects of cooking methods on polyphenols, pigments and antioxidant activity in potato tubers. LWT Food Sci. Technol. 2012, 45, 161–171. [Google Scholar] [CrossRef]
  107. Qiu, G.; Wang, D.; Song, X.; Deng, Y.; Zhao, Y. Degradation kinetics and antioxidant capacity of anthocyanins in air-impingement jet dried purple potato slices. Food Res. Int. 2018, 105, 121–128. [Google Scholar] [CrossRef]
  108. Rytel, E.; Tajner-Czopek, A.; Kita, A.; Kucharska, A.Z.; Sokół-Łętowska, A.; Hamouz, K. Content of anthocyanins and glycoalkaloids in blue-fleshed potatoes and changes in the content of α-solanine and α-chaconine during manufacture of fried and dried products. Int. J. Food Sci. Technol. 2018, 53, 719–727. [Google Scholar] [CrossRef]
  109. Zhang, L.; Zhao, L.; Bian, X.; Guo, K.; Zhou, L.; Wei, C. Characterization and comparative study of starches from seven purple sweet potatoes. Food Hydrocoll. 2018, 80, 168–176. [Google Scholar] [CrossRef]
  110. Li, A.; Xiao, R.; He, S.; An, X.; He, Y.; Wang, C.; Yin, S.; Wang, B.; Shi, X.; He, J. Research advances of purple sweet potato anthocyanins: extraction, identification, stability, bioactivity, application, and biotransformation. Molecules 2019, 24, 3816. [Google Scholar] [CrossRef] [Green Version]
  111. Suda, I.; Oki, T.; Masuda, M.; Kobayashi, M.; Nishiba, Y.; Furuta, S. Physiological functionality of purple-fleshed sweet potatoes containing anthocyanins and their utilization in foods. Jpn. Agric. Res. Q. 2003, 37, 167–173. [Google Scholar] [CrossRef]
  112. Bassa, I.A.; Francis, F.J. Stability of anthocyanins from sweet potatoes in a model beverage. J. Food Sci. 1987, 52, 1753–1754. [Google Scholar] [CrossRef]
  113. Drapal, M.; Rossel, G.; Heider, B.; Fraser, P.D. Metabolic diversity in sweet potato (Ipomoea batatas, L.) leaves and storage roots. Hortic. Res. 2019, 6, 2. [Google Scholar] [CrossRef] [Green Version]
  114. Rosero, A.; Granda, L.; Pérez, J.L.; Rosero, D.; Burgos-Paz, W.; Martínez, R.; Morelo, J.; Pastrana, I.; Burbano, E.; Morales, A. Morphometric and colourimetric tools to dissect morphological diversity: An application in sweet potato [Ipomoea batatas (L.) Lam.]. Genet. Resour. Crop Evol. 2019, 66, 1257–1278. [Google Scholar] [CrossRef] [Green Version]
  115. FAO. Statistics Division Production and Trade Statistics; FAO: Rome, Italy, 2017. [Google Scholar]
  116. Cui, R.; Zhu, F. Physicochemical properties and bioactive compounds of different varieties of sweetpotato flour treated with high hydrostatic pressure. Food Chem. 2019, 299, 125129. [Google Scholar] [CrossRef] [PubMed]
  117. De Albuquerque, T.M.R.; Sampaio, K.B.; de Souza, E.L. Sweet potato roots: Unrevealing an old food as a source of health promoting bioactive compounds–A review. Trends Food Sci. Technol. 2019, 85, 277–286. [Google Scholar] [CrossRef]
  118. Guo, K.; Liu, T.; Xu, A.; Zhang, L.; Bian, X.; Wei, C. Structural and functional properties of starches from root tubers of white, yellow, and purple sweet potatoes. Food Hydrocoll. 2019, 89, 829–836. [Google Scholar] [CrossRef]
  119. Wang, S.; Pan, D.; Lv, X.; Song, X.; Qiu, Z.; Huang, C.; Huang, R.; Chen, W. Proteomic approach reveals that starch degradation contributes to anthocyanin accumulation in tuberous root of purple sweet potato. J. Proteom. 2016, 143, 298–305. [Google Scholar] [CrossRef]
  120. Zhao, J.G.; Yan, Q.Q.; Xue, R.Y.; Zhang, J.; Zhang, Y.Q. Isolation and identification of colourless caffeoyl compounds in purple sweet potato by HPLC-DAD-ESI/MS and their antioxidant activities. Food Chem. 2014, 161, 22–26. [Google Scholar] [CrossRef]
  121. Kim, M.Y.; Lee, B.W.; Lee, H.; Lee, Y.Y.; Kim, M.H.; Lee, J.Y.; Lee, B.K.; Woo, K.S.; Kim, H. Phenolic compounds and antioxidant activity of sweet potato after heat treatment. J. Sci. Food Agric. 2019. [Google Scholar] [CrossRef]
  122. Moumouni Koala, A.H.; Somé, K.; Palé, E.; Sérémé, A.; Belem, J.; Nacro, M. Evaluation of eight orange fleshed sweetpotato (OFSP) varieties for their total antioxidant, total carotenoid and polyphenolic contents. Evaluation 2013, 3, 67–73. [Google Scholar]
  123. Neela, S.; Fanta, S.W. Review on nutritional composition of orange-fleshed sweet potato and its role in management of vitamin A deficiency. Food Sci. Nutr. 2019, 7, 1920–1945. [Google Scholar] [CrossRef] [Green Version]
  124. Lebot, V.; Michalet, S.; Legendre, L. Identification and quantification of phenolic compounds responsible for the antioxidant activity of sweet potatoes with different flesh colours using high performance thin layer chromatography (HPTLC). J. Food Compos. Anal. 2016, 49, 94–101. [Google Scholar] [CrossRef]
  125. Kubow, S.; Iskandar, M.M.; Sabally, K.; Azadi, B.; Sadeghi, S.; Kumarathasan, P.; Dhar, D.; Prakash, S.; Burgos, G. Biotransformation of anthocyanins from two purple-fleshed sweet potato accessions in a dynamic gastrointestinal system. Food Chem. 2016, 192, 171–177. [Google Scholar] [CrossRef] [PubMed]
  126. Meng, X.J.; Tan, C.; Feng, Y. Solvent extraction and in vitro simulated gastrointestinal digestion of phenolic compounds from purple sweet potato. Int. J. Food Sci. Technol. 2019, 2887–2896. [Google Scholar] [CrossRef]
  127. Oliveira, H.; Perez-Gregório, R.; de Freitas, V.; Mateus, N.; Fernandes, I. Comparison of the in vitro gastrointestinal bioavailability of acylated and non-acylated anthocyanins: Purple-fleshed sweet potato vs red wine. Food Chem. 2019, 276, 410–418. [Google Scholar] [CrossRef] [PubMed]
  128. Yang, Z.W.; Tang, C.E.; Zhang, J.L.; Zhou, Q.; Zhang, Z.C. Stability and antioxidant activity of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) subjected to simulated in vitro gastrointestinal digestion. Int. J. Food Sci. Technol. 2019, 2604–2614. [Google Scholar] [CrossRef]
  129. Sun, H.; Zhang, P.; Zhu, Y.; Lou, Q.; He, S. Antioxidant and prebiotic activity of five peonidin-based anthocyanins extracted from purple sweet potato (Ipomoea batatas (L.) Lam.). Sci. Rep. 2018, 8, 5018. [Google Scholar] [CrossRef] [PubMed]
  130. Esatbeyoglu, T.; Rodríguez-werner, M.; Schlösser, A.; Winterhalter, P.; Rimbach, G. Fractionation, enzyme inhibitory and cellular antioxidant activity of bioactives from purple sweet potato (Ipomoea batatas). Food Chem. 2017, 221, 447–456. [Google Scholar] [CrossRef]
  131. Gérard, V.; Ay, E.; Morlet-Savary, F.; Graff, B.; Galopin, C.; Ogren, T.; Mutilangi, W.; Lalevée, J. Thermal and photochemical stability of anthocyanins from black carrot, grape juice, and purple sweet potato in model beverages in the presence of ascorbic acid. J. Agric. Food Chem. 2019, 67, 5647–5660. [Google Scholar] [CrossRef]
  132. Gras, C.C.; Nemetz, N.; Carle, R.; Schweiggert, R.M. Anthocyanins from purple sweet potato (Ipomoea batatas (L.) Lam.) and their color modulation by the addition of phenolic acids and food-grade phenolic plant extracts. Food Chem. 2017, 235, 265–274. [Google Scholar] [CrossRef]
  133. He, W.; Zeng, M.; Chen, J.; Jiao, Y.; Niu, F.; Tao, G.; Zhang, S.; Qin, F.; He, Z. Identification and quantitation of anthocyanins in purple-fleshed sweet potatoes cultivated in China by UPLC-PDA and UPLC-QTOF-MS/MS. J. Agric. Food Chem. 2016, 64, 171–177. [Google Scholar] [CrossRef]
  134. Truong, V.D.; Nigel, D.; Thompson, R.T.; Mcfeeters, R.F.; Dean, L.O.; Pecota, K.V.; Yencho, G.C. Characterization of anthocyanins and anthocyanidins in purple-fleshed sweetpotatoes by HPLC-DAD/ESI-MS/MS. J. Agric. Food Chem. 2010, 58, 404–410. [Google Scholar] [CrossRef]
  135. Li, J.; Li, X.D.; Zhang, Y.; Zheng, Z.D.; Qu, Z.Y.; Liu, M.; Zhu, S.H.; Liu, S.; Wang, M.; Qu, L. Identification and thermal stability of purple-fleshed sweet potato anthocyanins in aqueous solutions with various pH values and fruit juices. Food Chem. 2013, 136, 1429–1434. [Google Scholar] [CrossRef] [PubMed]
  136. Cai, Z.; Song, L.; Qian, B.; Xu, W.; Ren, J.; Jing, P.; Oey, I. Understanding the effect of anthocyanins extracted from purple sweet potatoes on alcohol-induced liver injury in mice. Food Chem. 2018, 245, 463–470. [Google Scholar] [CrossRef] [PubMed]
  137. Jang, H.H.; Kim, H.W.; Kim, S.Y.; Kim, S.M.; Kim, J.B.; Lee, Y.M. In vitro and in vivo hypoglycemic effects of cyanidin 3-caffeoyl-p-hydroxybenzoylsophoroside-5-glucoside, an anthocyanin isolated from purple-fleshed sweet potato. Food Chem. 2019, 272, 688–693. [Google Scholar] [CrossRef] [PubMed]
  138. Wang, L.; Zhao, Y.; Zhou, Q.; Luo, C.L.; Deng, A.P.; Zhang, Z.C.; Zhang, J.L. Characterization and hepatoprotective activity of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8). J. Food Drug Anal. 2017, 25, 607–618. [Google Scholar] [CrossRef] [Green Version]
  139. Xu, J.; Su, X.; Lim, S.; Griffin, J.; Carey, E.; Katz, B.; Tomich, J.; Smith, J.S.; Wang, W. Characterisation and stability of anthocyanins in purple-fleshed sweet potato P40. Food Chem. 2015, 186, 90–96. [Google Scholar] [CrossRef] [Green Version]
  140. Laksmiani, N.P.L.; Widiastari, M.I.; Reynaldi, K.R. The inhibitory activity of peonidin purple sweet potato in human epidermal receptor-2 receptor (her-2) expression by in silico study. J. Phys. Conf. Ser. 2018, 1040, 012010. [Google Scholar] [CrossRef] [Green Version]
  141. Luo, C.; Zhou, Q.; Yang, Z.; Wang, R.; Zhang, J. Evaluation of structure and bioprotective activity of key high molecular weight acylated anthocyanin compounds isolated from the purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8 ). Food Chem. 2018, 241, 23–31. [Google Scholar] [CrossRef]
  142. Lu, J.; Wu, D.M.; Zheng, Y.L.; Hu, B.; Cheng, W.; Zhang, Z.F. Purple sweet potato color attenuates domoic acid-induced cognitive deficits by promoting estrogen receptor-α-mediated mitochondrial biogenesis signaling in mice. Free Radic. Biol. Med. 2012, 52, 646–659. [Google Scholar] [CrossRef]
  143. Zhuang, J.; Lu, J.; Wang, X.; Wang, X.; Hu, W.; Hong, F.; Zhao, X.X.; Zheng, Y. lin Purple sweet potato color protects against high-fat diet-induced cognitive deficits through AMPK-mediated autophagy in mouse hippocampus. J. Nutr. Biochem. 2019, 65, 35–45. [Google Scholar] [CrossRef]
  144. Li, J.; Shi, Z.; Mi, Y. Purple sweet potato color attenuates high fat-induced neuroinflammation in mouse brain by inhibiting mapk and NF-κB activation. Mol. Med. Rep. 2018, 17, 4823–4831. [Google Scholar] [CrossRef]
  145. Li, W.L.; Yu, H.Y.; Zhang, X.J.; Ke, M.; Hong, T. Purple sweet potato anthocyanin exerts antitumor effect in bladder cancer. Oncol. Rep. 2018, 40, 73–82. [Google Scholar] [CrossRef]
  146. Schmitt, E.; Stopper, H. Estrogenic activity of naturally occurring anthocyanidins. Nutr. Cancer 2001, 41, 145–149. [Google Scholar] [CrossRef]
  147. Yoshimoto, M.; Okuno, S.; Yamaguchi, M.; Yamakawa, O. Antimutagenicity of deacylated anthocyanins in purple-fleshed sweetpotato. Biosci. Biotechnol. Biochem. 2001, 65, 1652–1655. [Google Scholar] [CrossRef] [PubMed]
  148. Zhao, J.G.; Yan, Q.Q.; Lu, L.Z.; Zhang, Y.Q. In vivo antioxidant, hypoglycemic, and anti-tumor activities of anthocyanin extracts from purple sweet potato. Nutr. Res. Pract. 2013, 7, 359–365. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  149. Zhang, Z.; Zhou, Q.; Yang, Y.; Wang, Y.; Zhang, J. Highly Acylated Anthocyanins from purple sweet potato (Ipomoea batatas L.) alleviate hyperuricemia and kidney inflammation in hyperuricemic mice: Possible attenuation effects on allopurinol. J. Agric. Food Chem. 2019, 67, 6202–6211. [Google Scholar] [CrossRef] [PubMed]
  150. Zheng, G.H.; Shan, Q.; Mu, J.J.; Wang, Y.J.; Zhang, Z.F.; Fan, S.H.; Hu, B.; Li, M.Q.; Xie, J.; Chen, P.; et al. Purple sweet potato color attenuates kidney damage by blocking VEGFR2/ROS/NLRP3 signaling in high-fat diet-treated mice. Oxid. Med. Cell. Longev. 2019, 2019. [Google Scholar] [CrossRef]
  151. Jiang, Z.; Chen, C.; Xie, W.; Wang, M.; Wang, J.; Zhang, X. Anthocyanins attenuate alcohol-induced hepatic injury by inhibiting pro-inflammation signalling. Nat. Prod. Res. 2016, 30, 469–473. [Google Scholar] [CrossRef]
  152. Valenti, L.; Riso, P.; Mazzocchi, A.; Porrini, M.; Fargion, S.; Agostoni, C. Dietary anthocyanins as nutritional therapy for nonalcoholic fatty liver disease. Oxid. Med. Cell. Longev. 2013, 2013. [Google Scholar] [CrossRef] [Green Version]
  153. Del Rio, D.; Rodriguez-Mateos, A.; Spencer, J.P.E.; Tognolini, M.; Borges, G.; Crozier, A. Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases. Antioxid. Redox Signal. 2012, 18, 1818–1892. [Google Scholar] [CrossRef] [Green Version]
  154. Han, K.H.; Shimada, K.I.; Sekikawa, M.; Fukushima, M. Anthocyanin-rich red potato flakes affect serum lipid peroxidation and hepatic SOD mRNA level in rats. Biosci. Biotechnol. Biochem. 2007, 71, 1356–1359. [Google Scholar] [CrossRef]
  155. Hwang, Y.P.; Choi, J.H.; Choi, J.M.; Chung, Y.C.; Jeong, H.G. Protective mechanisms of anthocyanins from purple sweet potato against tert-butyl hydroperoxide-induced hepatotoxicity. Food Chem. Toxicol. 2011, 49, 2081–2089. [Google Scholar] [CrossRef] [PubMed]
  156. Suda, I.; Ishikawa, F.; Hatakeyama, M.; Miyawaki, M.; Kudo, T.; Hirano, K.; Ito, A.; Yamakawa, O.; Horiuchi, S. Intake of purple sweet potato beverage affects on serum hepatic biomarker levels of healthy adult men with borderline hepatitis. Eur. J. Clin. Nutr. 2008, 62, 60–67. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  157. Zhang, Z.F.; Lu, J.; Zheng, Y.L.; Wu, D.M.; Hu, B.; Shan, Q.; Cheng, W.; Li, M.Q.; Sun, Y.Y. Purple sweet potato color attenuates hepatic insulin resistance via blocking oxidative stress and endoplasmic reticulum stress in high-fat-diet-treated mice. J. Nutr. Biochem. 2013, 24, 1008–1018. [Google Scholar] [CrossRef] [PubMed]
  158. Qin, S.; Sun, D.; Mu, J.; Ma, D.; Tang, R.; Zheng, Y. Purple sweet potato color improves hippocampal insulin resistance via down-regulating SOCS3 and galectin-3 in high-fat diet mice. Behav. Brain Res. 2019, 359, 370–377. [Google Scholar] [CrossRef] [PubMed]
  159. Wang, X.; Zhang, Z.F.; Zheng, G.H.; Wang, A.M.; Sun, C.H.; Qin, S.P.; Zhuang, J.; Lu, J.; Ma, D.F.; Zheng, Y.L. The inhibitory effects of purple sweet potato color on hepatic inflammation is associated with restoration of NAD+ levels and attenuation of nlrp3 inflammasome activation in high-fat-diet-treated mice. Molecules 2017, 22, 1315. [Google Scholar] [CrossRef] [PubMed]
  160. Gofur, A.; Witjoro, A.; Ningtiyas, E.W.; Setyowati, E.; Mukharromah, S.A.; Athoillah, M.F.; Lestari, S.R. The evaluation of dietary black soybean and purple sweet potato on insulin sensitivity in streptozotocin-induced diabetic rats. Pharmacogn. J. 2019, 11, 639–646. [Google Scholar] [CrossRef] [Green Version]
  161. Park, S.-J.; Lee, D.; Lee, M.; Kwon, H.-O.; Kim, H.; Park, J.; Jeon, W.; Cha, M.; Jun, S.; Park, K.; et al. The Effects of Curcuma longa L., Purple sweet potato, and mixtures of the two on immunomodulation in C57BL/6J mice infected with LP-BM5 murine leukemia retrovirus. J. Med. Food 2018, 21, 689–700. [Google Scholar] [CrossRef]
  162. Ju, R.; Zheng, S.; Luo, H.; Wang, C.; Duan, L.; Sheng, Y.; Zhao, C.; Xu, W.; Huang, K. Purple Sweet Potato Attenuate Weight Gain in High Fat Diet Induced Obese Mice. J. Food Sci. 2017, 82, 787–793. [Google Scholar] [CrossRef]
  163. Chen, H.; Sun, J.; Liu, J.; Gou, Y.; Zhang, X.; Wu, X.; Sun, R.; Tang, S.; Kan, J.; Qian, C.; et al. Structural characterization and anti-inflammatory activity of alkali-soluble polysaccharides from purple sweet potato. Int. J. Biol. Macromol. 2019, 131, 484–494. [Google Scholar] [CrossRef]
  164. Gou, Y.; Sun, J.; Liu, J.; Chen, H.; Kan, J.; Qian, C.; Zhang, N.; Jin, C. Structural characterization of a water-soluble purple sweet potato polysaccharide and its effect on intestinal inflammation in mice. J. Funct. Foods 2019, 61, 103502. [Google Scholar] [CrossRef]
  165. Sun, J.; Zhou, B.; Tang, C.; Gou, Y.; Chen, H.; Wang, Y.; Jin, C.; Liu, J.; Niu, F.; Kan, J.; et al. Characterization, antioxidant activity and hepatoprotective effect of purple sweetpotato polysaccharides. Int. J. Biol. Macromol. 2018, 115, 69–76. [Google Scholar] [CrossRef] [PubMed]
  166. Tang, C.; Sun, J.; Liu, J.; Jin, C.; Wu, X.; Zhang, X.; Chen, H.; Gou, Y.; Kan, J.; Qian, C.; et al. Immune-enhancing effects of polysaccharides from purple sweet potato. Int. J. Biol. Macromol. 2019, 123, 923–930. [Google Scholar] [CrossRef] [PubMed]
  167. Tang, C.; Sun, J.; Zhou, B.; Jin, C.; Liu, J.; Gou, Y.; Chen, H.; Kan, J.; Qian, C.; Zhang, N. Immunomodulatory effects of polysaccharides from purple sweet potato on lipopolysaccharide treated RAW 264.7 macrophages. J. Food Biochem. 2018, 42, e12535. [Google Scholar] [CrossRef]
  168. Tang, C.; Sun, J.; Zhou, B.; Jin, C.; Liu, J.; Kan, J.; Qian, C.; Zhang, N. Effects of polysaccharides from purple sweet potatoes on immune response and gut microbiota composition in normal and cyclophosphamide treated mice. Food Funct. 2018, 9, 937–950. [Google Scholar] [CrossRef]
  169. Jiang, T.; Mao, Y.; Sui, L.; Yang, N.; Li, S.; Zhu, Z.; Wang, C.; Yin, S.; He, J.; He, Y. Degradation of anthocyanins and polymeric color formation during heat treatment of purple sweet potato extract at different pH. Food Chem. 2019, 274, 460–470. [Google Scholar] [CrossRef]
  170. Quan, W.; He, W.; Lu, M.; Yuan, B.; Zeng, M.; Gao, D.; Qin, F.; Chen, J.; He, Z. Anthocyanin composition and storage degradation kinetics of anthocyanins-based natural food colourant from purple-fleshed sweet potato. Int. J. Food Sci. Technol. 2019, 54, 2529–2539. [Google Scholar] [CrossRef]
  171. Thi Lan Khanh, P.; Chittrakorn, S.; Rutnakornpituk, B.; Phan Tai, H.; Ruttarattanamongkol, K. Processing effects on anthocyanins, phenolic acids, antioxidant activity, and physical characteristics of Vietnamese purple-fleshed sweet potato flours. J. Food Process. Preserv. 2018, 42, e13722. [Google Scholar] [CrossRef]
  172. Yea, C.S.; Nevara, G.A.; Muhammad, K.; Ghazali, H.M.; Karim, R. Physical properties, resistant starch content and antioxidant profile of purple sweet potato powder after 12 months of storage. Int. J. Food Prop. 2019, 22, 974–984. [Google Scholar] [CrossRef] [Green Version]
  173. Lagnika, C.; Jiang, N.; Song, J.; Li, D.; Liu, C.; Huang, J.; Wei, Q.; Zhang, M. Effects of pretreatments on properties of microwave-vacuum drying of sweet potato slices. Dry. Technol. 2018, 37, 1901–1914. [Google Scholar] [CrossRef]
  174. Phan, K.T.L.; Chittrakorn, S.; Tai, H.P.; Ruttarattanamongkol, K. Effects of cooking methods on the changes of total anthocyanins, phenolics content and physical characteristics of purple-fleshed sweet potato (Ipomoea batatas L.) grown in Vietnam. Int. J. Adv. Sci. Eng. Inf. Technol. 2018, 8, 227–233. [Google Scholar] [CrossRef]
  175. Kamiloglu, S.; Van Camp, J.; Capanoglu, E. Black carrot polyphenols: Effect of processing, storage and digestion—An overview. Phytochem. Rev. 2018, 17, 379–395. [Google Scholar] [CrossRef]
  176. Arscott, S.A.; Tanumihardjo, S.A. Carrots of many colors provide basic nutrition and bioavailable phytochemicals acting as a functional food. Compr. Rev. Food Sci. Food Saf. 2010, 9, 223–239. [Google Scholar] [CrossRef]
  177. Kamiloglu, S.; Capanoglu, E.; Bilen, F.D.; Gonzales, G.B.; Grootaert, C.; Van de Wiele, T.; Van Camp, J. Bioaccessibility of polyphenols from plant-processing byproducts of black carrot (Daucus carota L.). J. Agric. Food Chem. 2016, 64, 2450–2458. [Google Scholar] [CrossRef] [PubMed]
  178. Kamiloglu, S.; Pasli, A.A.; Ozcelik, B.; Van Camp, J.; Capanoglu, E. Influence of different processing and storage conditions on in vitro bioaccessibility of polyphenols in black carrot jams and marmalades. Food Chem. 2015, 186, 74–82. [Google Scholar] [CrossRef] [PubMed]
  179. Kumar, M.; Dahuja, A.; Sachdev, A.; Kaur, C.; Varghese, E.; Saha, S.; Sairam, K.V.S.S. Black Carrot (Daucus carota ssp.) and Black Soybean (Glycine max (L.) Merr.) Anthocyanin Extract: A Remedy to Enhance Stability and Functionality of Fruit Juices by Copigmentation, Waste and Biomass Valorization; Springer: Berlin/Heidelberg, Germany, 2018. [Google Scholar]
  180. Horvitz, M.A.; Simon, P.W.; Tanumihardjo, S.A. Lycopene and β-carotene are bioavailable from lycopene “red” carrots in humans. Eur. J. Clin. Nutr. 2004, 58, 803–811. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  181. Kammerer, D.; Carle, R.; Schieber, A. Quantification of anthocyanins in black carrot extracts (Daucus carota ssp. sativus var. atrorubens Alef.) and evaluation of their color properties. Eur. Food Res. Technol. 2004, 219, 479–486. [Google Scholar] [CrossRef]
  182. Smeriglio, A.; Denaro, M.; Barreca, D.; D’Angelo, V.; Germanò, M.P.; Trombetta, D. Polyphenolic profile and biological activities of black carrot crude extract (Daucus carota L. ssp. sativus var. atrorubens Alef.). Fitoterapia 2018, 124, 49–57. [Google Scholar] [CrossRef]
  183. Olejnik, A.; Rychlik, J.; Kidoń, M.; Czapski, J.; Kowalska, K.; Juzwa, W.; Olkowicz, M.; Dembczyński, R.; Moyer, M.P. Antioxidant effects of gastrointestinal digested purple carrot extract on the human cells of colonic mucosa. Food Chem. 2016, 190, 1069–1077. [Google Scholar] [CrossRef]
  184. Blando, F.; Calabriso, N.; Berland, H.; Maiorano, G.; Gerardi, C.; Carluccio, M.A.; Andersen, Ø.M. Radical scavenging and anti-inflammatory activities of representative anthocyanin groupings from pigment-rich fruits and vegetables. Int. J. Mol. Sci. 2018, 19, 169. [Google Scholar] [CrossRef] [Green Version]
  185. Kammerer, D.; Carle, R.; Schieber, A. Characterization of phenolic acids in black carrots (Daucus carota ssp. sativus var. atrorubens Alef.) by high-performance liquid chromatography/ electrospray ionization mass spectrometry. Rapid Commun. Mass Spectrom. 2004, 18, 1331–1340. [Google Scholar] [CrossRef]
  186. Khandare, V.; Walia, S.; Singh, M.; Kaur, C. Black carrot (Daucus carota ssp. sativus) juice: Processing effects on antioxidant composition and color. Food Bioprod. Process. 2011, 89, 482–486. [Google Scholar] [CrossRef]
  187. Iliopoulou, I.; Thaeron, D.; Baker, A.; Jones, A.; Robertson, N. Analysis of the thermal degradation of the individual anthocyanin compounds of black carrot (Daucus carota L.): A new approach using high-resolution proton nuclear magnetic resonance spectroscopy. J. Agric. Food Chem. 2015, 63, 7066–7073. [Google Scholar] [CrossRef] [PubMed]
  188. Santana-Gálvez, J.; Pérez-Carrillo, E.; Velázquez-Reyes, H.H.; Cisneros-Zevallos, L.; Jacobo-Velázquez, D.A. Application of wounding stress to produce a nutraceutical-rich carrot powder ingredient and its incorporation to nixtamalized corn flour tortillas. J. Funct. Foods 2016, 27, 655–666. [Google Scholar] [CrossRef]
  189. Wang, M.; Lopez-Nieves, S.; Goldman, I.L.; Maeda, H.A. Limited tyrosine utilization explains lower betalain contents in yellow than in red table beet genotypes. J. Agric. Food Chem. 2017, 65, 4305–4313. [Google Scholar] [CrossRef]
  190. Herbach, K.; Stintzing, F.; Carle, R. Impact of thermal treatment on color and pigment pattern of red beet (Beta vulgaris L.) preparations. J. Food Sci. 2004, 69, 419–498. [Google Scholar] [CrossRef]
  191. Montes-Lora, S.; Rodríguez-Pulido, F.J.; Cejudo-Bastante, M.J.; Heredia, F.J. Implications of the red beet ripening on the colour and betalain composition relationships. Plant Foods Hum. Nutr. 2018, 73, 216–221. [Google Scholar] [CrossRef]
  192. Wettasinghe, M.; Bolling, B.; Plhak, L.; Xiao, H.; Parkin, K. Phase II enzyme-inducing and antioxidant activities of beetroot (Beta vulgaris L.) extracts from phenotypes of different pigmentation. J. Agric. Food Chem. 2002, 50, 6704–6709. [Google Scholar] [CrossRef]
  193. Vulić, J.J.; Ćebović, T.N.; Čanadanović-Brunet, J.M.; Ćetković, G.S.; Čanadanović, V.M.; Djilas, S.M.; Šaponjac, V.T.T. In vivo and in vitro antioxidant effects of beetroot pomace extracts. J. Funct. Foods 2014, 6, 168–175. [Google Scholar] [CrossRef]
  194. Leng, M.S.; Tobit, P.; Demasse, A.M.; Wolf, K.; Gouado, I.; Ndjouenkeu, R.; Rawel, H.M.; Schweigert, F.J. Nutritional and anti-oxidant properties of yam (Dioscorea schimperiana) based complementary food formulation. Sci. African 2019, 5, e00132. [Google Scholar] [CrossRef]
  195. Champagne, A.; Hilbert, G.; Legendre, L.; Lebot, V. Diversity of anthocyanins and other phenolic compounds among tropical root crops from Vanuatu, South Pacific. J. Food Compos. Anal. 2011, 24, 315–325. [Google Scholar] [CrossRef]
  196. Li, T.; Teng, H.; An, F.; Huang, Q.; Chen, L.; Song, H. The beneficial effects of purple yam (Dioscorea alata L.) resistant starch on hyperlipidemia in high-fat-fed hamsters. Food Funct. 2019, 10, 2642–2650. [Google Scholar] [CrossRef]
  197. Patel, K.S.; Karmakar, N.; Desai, K.D.; Narwade, A.V.; Chakravarty, G.; Debnath, M.K. Exploring of greater yam (Dioscorea alata L.) genotypes through biochemical screening for better cultivation in south Gujarat zone of India. Physiol. Mol. Biol. Plants 2019, 25, 1235–1249. [Google Scholar] [CrossRef]
  198. Li, T.; Chen, L.; Xiao, J.; An, F.; Wan, C.; Song, H. Prebiotic effects of resistant starch from purple yam (Dioscorea alata L.) on the tolerance and proliferation ability of Bifidobacterium adolescentis in vitro. Food Funct. 2018, 9, 2416–2425. [Google Scholar] [CrossRef]
  199. Estiasih, T.; Umaro, D.; Harijono, H. Hypoglycemic effect of crude water soluble polysaccharide extracted from tubers of purple and yellow water yam (Dioscorea alata L.) on alloxan-induced hyperglycemia Wistar rats. Prog. Nutr. 2018, 20, 59–67. [Google Scholar]
  200. Rosida; Purnawati, A.; Susiloningsih, E.K. Hypocholesterolemic and hypoglycemic effects of autoclaved-cooled water yam (Dioscorea alata) on hypercholesterolemia rats. Int. Food Res. J. 2018, 25, S181–S184. [Google Scholar]
  201. Chen, C.T.; Wang, Z.H.; Hsu, C.C.; Lin, H.H.; Chen, J.H. Taiwanese and Japanese yam (Dioscorea spp.) extracts attenuate doxorubicin-induced cardiotoxicity in mice. J. Food Drug Anal. 2017, 25, 872–880. [Google Scholar] [CrossRef] [Green Version]
  202. Khan, R.; Upaganlawar, A.B.; Upasani, C. Protective effects of Dioscorea alata L. in aniline exposure-induced spleen toxicity in rats: A biochemical study. Toxicol. Int. 2014, 21, 294–299. [Google Scholar]
  203. Chiu, C.S.; Deng, J.S.; Chang, H.Y.; Chen, Y.C.; Lee, M.M.; Hou, W.C.; Lee, C.Y.; Huang, S.S.; Huang, G.J. Antioxidant and anti-inflammatory properties of taiwanese yam (Dioscorea japonica Thunb. var. pseudojaponica (Hayata) Yamam.) and its reference compounds. Food Chem. 2013, 141, 1087–1096. [Google Scholar] [CrossRef]
  204. Chang, W.T.; Chen, H.M.; Yin, S.Y.; Chen, Y.H.; Wen, C.C.; Wei, W.C.; Lai, P.; Wang, C.H.; Yang, N.S. Specific dioscorea phytoextracts enhance potency of TCL-loaded DC-based cancer vaccines. Evidence-Based Complement. Altern. Med. 2013, 2013. [Google Scholar] [CrossRef] [Green Version]
  205. Liu, S.F.; Chang, S.Y.; Lee, T.C.; Chuang, L.Y.; Guh, J.Y.; Hung, C.Y.; Hung, T.J.; Hung, Y.J.; Chen, P.Y.; Hsieh, P.F.; et al. Dioscorea alata attenuates renal interstitial cellular fibrosis by regulating smad- and epithelial-mesenchymal transition signaling pathways. PLoS ONE 2012, 7, e47482. [Google Scholar] [CrossRef] [Green Version]
  206. Chan, Y.C.; Chang, S.C.; Liu, S.Y.; Yang, H.L.; Hseu, Y.C.; Liao, J.W. Beneficial effects of yam on carbon tetrachloride-induced hepatic fibrosis in rats. J. Sci. Food Agric. 2010, 90, 161–167. [Google Scholar] [CrossRef]
  207. Wang, C.-H.; Tsai, C.-H.; Lin, H.-J.; Wang, T.-C.; Chen, H.-L. Uncooked Taiwanese yam (Dioscorea alata L. cv. Tainung No. 2) beneficially modulated the large bowel function and faecal microflora in BALB/c mice. J. Sci. Food Agric. 2006, 87, 1374–1380. [Google Scholar] [CrossRef]
  208. Hsu, C.C.; Huang, Y.C.; Yin, M.C.; Lin, S.J. Effect of yam (Dioscorea alata compared to Dioscorea japonica) on gastrointestinal function and antioxidant activity in mice. J. Food Sci. 2006, 71, 5–8. [Google Scholar] [CrossRef]
  209. Chan, Y.-C.; Hsu, C.-K.; Wang, M.-F.; Liao, J.-W.; Su, T.-Y. Beneficial effect of yam on the amyloid β-protein, monoamine oxidase B and cognitive deficit in mice with accelerated senescence. J. Sci. Food Agric. 2006, 86, 1517–1525. [Google Scholar] [CrossRef]
  210. Chan, Y.C.; Hsu, C.K.; Wang, M.F.; Su, T.Y. A diet containing yam reduces the cognitive deterioration and brain lipid peroxidation in mice with senescence accelerated. Int. J. Food Sci. Technol. 2004, 39, 99–107. [Google Scholar] [CrossRef]
  211. Fu, S.L.; Hsu, Y.H.; Lee, P.Y.; Hou, W.C.; Hung, L.C.; Lin, C.H.; Chen, C.M.; Huang, Y.J. Dioscorin isolated from Dioscorea alata activates TLR4-signaling pathways and induces cytokine expression in macrophages. Biochem. Biophys. Res. Commun. 2006, 339, 137–144. [Google Scholar] [CrossRef]
  212. Mahmad, N.; Taha, R.M.; Othman, R.; Abdullah, S.; Anuar, N.; Elias, H.; Rawi, N. Anthocyanin as potential source for antimicrobial activity in Clitoria ternatea L. and Dioscorea alata L. Pigment Resin Technol. 2018, 47, 490–495. [Google Scholar] [CrossRef]
  213. Chen, T.; Hu, S.; Zhang, H.; Guan, Q.; Yang, Y.; Wang, X. Anti-inflammatory effects of Dioscorea alata L. anthocyanins in a TNBS-induced colitis model. Food Funct. 2017, 8, 659–669. [Google Scholar] [CrossRef]
  214. Guo, X.; Sha, X.; Cai, S.; Wang, O.; Ji, B. Antiglycative and antioxidative properties of ethyl acetate fraction of Chinese purple yam (Dioscorea alata L.) extracts. Food Sci. Technol. Res. 2015, 21, 563–571. [Google Scholar] [CrossRef] [Green Version]
  215. Guo, X.X.; Sha, X.H.; Liu, J.; Cai, S.B.; Wang, Y.; Ji, B.P. Chinese purple yam (Dioscorea alata L.) extracts inhibit diabetes-related enzymes and protect HepG2 cells against oxidative stress and insulin resistance induced by FFA. Food Sci. Technol. Res. 2015, 21, 677–683. [Google Scholar] [CrossRef] [Green Version]
  216. Mahmoudian-Sani, M.R.; Asadi-Samani, M.; Luther, T.; Saeedi-Boroujeni, A.; Gholamian, N. A new approach for treatment of type 1 diabetes: Phytotherapy and phytopharmacology of regulatory T cells. J. Ren. Inj. Prev. 2017, 6, 158–163. [Google Scholar] [CrossRef] [Green Version]
  217. Zhang, J.; Tian, H.; Zhan, P.; Du, F.; Zong, A.; Xu, T. Isolation and identification of phenolic compounds in Chinese purple yam and evaluation of antioxidant activity. LWT Food Sci. Technol. 2018, 96, 161–165. [Google Scholar] [CrossRef]
  218. Dey, P.; Ray, S.; Chaudhuri, T.K. Immunomodulatory activities and phytochemical characterisation of the methanolic extract of Dioscorea alata aerial tuber. J. Funct. Foods 2016, 23, 315–328. [Google Scholar] [CrossRef]
  219. Lu, J.; Wong, R.N.S.; Zhang, L.; Wong, R.Y.L.; Ng, T.B.; Lee, K.F.; Zhang, Y.B.; Lao, L.X.; Liu, J.Y.; Sze, S.C.W. Comparative Analysis of Proteins with Stimulating Activity on Ovarian Estradiol Biosynthesis from Four Different Dioscorea Species in vitro Using Both Phenotypic and Target-based Approaches: Implication for Treating Menopause. Appl. Biochem. Biotechnol. 2016, 180, 79–93. [Google Scholar] [CrossRef]
  220. Wu, Z.G.; Jiang, W.; Nitin, M.; Bao, X.Q.; Chen, S.L.; Tao, Z.M. Characterizing diversity based on nutritional and bioactive compositions of yam germplasm (Dioscorea spp.) commonly cultivated in China. J. Food Drug Anal. 2016, 24, 367–375. [Google Scholar] [CrossRef] [Green Version]
  221. Han, C.H.; Liu, J.C.; Fang, S.U.; Hou, W.C. Antioxidant activities of the synthesized thiol-contained peptides derived from computer-aided pepsin hydrolysis of yam tuber storage protein, dioscorin. Food Chem. 2013, 138, 923–930. [Google Scholar] [CrossRef]
  222. Koo, H.J.; Park, H.J.; Byeon, H.E.; Kwak, J.H.; Um, S.H.; Kwon, S.T.; Rhee, D.K.; Pyo, S. Chinese yam extracts containing β-sitosterol and ethyl linoleate protect against atherosclerosis in apolipoprotein e-deficient mice and inhibit muscular expression of VCAM-1 in vitro. J. Food Sci. 2014, 79, H719–H729. [Google Scholar] [CrossRef]
  223. Harijono, T.E.; Ariestiningsih, A.D.; Wardani, N.A.K. The effect of crude diosgenin extract from purple and yellow greater yams (Dioscorea alata) on the lipid profile of dyslipidemia rats. Emirates J. Food Agric. 2016, 28, 506–512. [Google Scholar] [CrossRef] [Green Version]
  224. Lee, Y.C.; Lin, J.T.; Wang, C.K.; Chen, C.H.; Yang, D.J. Antiproliferative effects of fractions of furostanol and spirostanol glycosides from yam (Dioscorea pseudojaponica Yamamoto) and diosgenin on cancer and normal cells and their apoptotic effects for MCF-7 cells. J. Food Biochem. 2012, 36, 75–85. [Google Scholar] [CrossRef]
  225. Jailani, F.; Kusumawardani, S.; Puspitasari, C.; Maula, A.; Purwandari, U. Annealled purple yam (Dioscorea alata var. purpurea) flour improved gelatinisation profile, but increased glycemic index of substituted bread. Int. Food Res. J. 2013, 20, 865–871. [Google Scholar]
  226. Hsu, C.L.; Hurang, S.L.; Chen, W.; Weng, Y.M.; Tseng, C.Y. Qualities and antioxidant properties of bread as affected by the incorporation of yam flour in the formulation. Int. J. Food Sci. Technol. 2004, 39, 231–238. [Google Scholar] [CrossRef]
  227. Li, P.H.; Huang, C.C.; Yang, M.Y.; Wang, C.C.R. Textural and sensory properties of salted noodles containing purple yam flour. Food Res. Int. 2012, 47, 223–228. [Google Scholar] [CrossRef]
  228. Seguchi, M.; Ozawa, M.; Nakamura, C.; Tabara, A. Development of gluten-free bread baked with yam flour. Food Sci. Technol. Res. 2012, 18, 543–548. [Google Scholar] [CrossRef] [Green Version]
  229. Brewster, J.L. Onions and Other Vegetable Alliums, 2nd ed.; CABI: Wallingford, UK, 2008; ISBN 9781845933999. [Google Scholar]
  230. Slimestad, R.; Fossen, T.; Vågen, I.M. Onions: A source of unique dietary flavonoids. J. Agric. Food Chem. 2007, 55, 10067–10080. [Google Scholar] [CrossRef]
  231. Benkeblia, N. Free-Radical Scavenging capacity and antioxidant properties of some selected onions (Allium cepa L.) and garlic ( Allium sativum L.) extracts. Brazilian Arch. Biol. Technol. 2005, 48, 753–759. [Google Scholar] [CrossRef]
  232. Zhang, S.; Deng, P.; Xu, Y.C.; Lü, S.W.; Wang, J.J. Quantification and analysis of anthocyanin and flavonoids compositions, and antioxidant activities in onions with three different colors. J. Integr. Agric. 2016, 15, 2175–2181. [Google Scholar] [CrossRef] [Green Version]
  233. Oboh, G.; Ademiluyi, A.O.; Agunloye, O.M.; Ademosun, A.O.; Ogunsakin, B.G. Inhibitory Effect of garlic, purple onion, and white onion on key enzymes linked with type 2 diabetes and hypertension. J. Diet. Suppl. 2019, 16, 105–118. [Google Scholar] [CrossRef]
  234. Albishi, T.; John, J.A.; Al-Khalifa, A.S.; Shahidi, F. Antioxidant, anti-inflammatory and DNA scission inhibitory activities of phenolic compounds in selected onion and potato varieties. J. Funct. Foods 2013, 5, 930–939. [Google Scholar] [CrossRef]
  235. Ou, B.; Huang, D.; Hampsch-Woodill, M.; Flanagan, J.A.; Deemer, E.K. Analysis of antioxidant activities of common vegetables employing oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays: A comparative study. J. Agric. Food Chem. 2002, 50, 3122–3128. [Google Scholar] [CrossRef]
  236. Khiari, Z.; Makris, D.P.; Kefalas, P. An Investigation on the Recovery of Antioxidant Phenolics from Onion Solid Wastes Employing Water/Ethanol-Based Solvent Systems. Food Process. Technol. 2009, 2, 337–343. [Google Scholar] [CrossRef]
  237. Hanlon, P.R.; Barnes, D.M. Phytochemical composition and biological activity of 8 varieties of radish (Raphanus sativus L.) sprouts and mature taproots. J. Food Sci. 2011, 76, 185–192. [Google Scholar] [CrossRef]
  238. Masukawa, T.; Kadowaki, M.; Matsumoto, T.; Nakatsuka, A.; Cheon, K.S.; Kato, K.; Tatsuzawa, F.; Kobayashi, N. Enhancement of food functionality of a local pungent radish “izumo orochi daikon” ‘susanoo’ by introduction of a colored root character. Hortic. J. 2018, 87, 356–363. [Google Scholar] [CrossRef]
  239. Tatsuzawa, F.; Saito, N.; Toki, K.; Shinoda, K.; Shigihara, A.; Honda, T. Acylated cyanidin 3-sophoroside-5-glucosides from the purple roots of red radish (Raphanus sativus L.) “Benikanmi.”. J. Jpn. Soc. Hortic. Sci. 2010, 79, 103–107. [Google Scholar] [CrossRef]
  240. Ahn, M.; Koh, R.; Kim, G.O.; Shin, T. Aqueous extract of purple Bordeaux radish, Raphanus sativus L. ameliorates ethanol-induced gastric injury in rats. Orient. Pharm. Exp. Med. 2013, 13, 247–252. [Google Scholar] [CrossRef]
  241. Pak, W.M.; Kim, K.B.W.R.; Kim, M.J.; Kang, B.K.; Bark, S.W.; Kim, B.R.; Ahn, N.K.; Choi, Y.U.; Yoon, S.R.; Ahn, D.H. Antioxidative effect of extracts from different parts of Kohlrabi. J. Appl. Biol. Chem. 2014, 57, 353–358. [Google Scholar] [CrossRef]
  242. Jung, H.A.; Karki, S.; Ehom, N.; Yoon, M.; Kim, E.J.; Choi, J.S. Anti-diabetic and anti-inflammatory effects of green and red kohlrabi cultivars (Brassica oleracea var. gongylodes). 2014, 19, 281–290. [Google Scholar] [CrossRef] [Green Version]
  243. Paull, R.E.; Uruu, G.; Arakaki, A. Variation in the cooked and chipping quality of taro. Horttechnology 2000, 10, 823–829. [Google Scholar] [CrossRef] [Green Version]
  244. Beyene, T.M. Morpho−Agronomical Characterization of Taro (Colocasia esculenta) Accessions in Ethiopia. Plant 2013, 1, 1–9. [Google Scholar] [CrossRef] [Green Version]
Antioxidants 08 00617 g001 550
Figure 1. The core structure of anthocyanins with two aromatic benzol rings (A and B rings) and a portion cyclized with oxygen (C ring).
Figure 1. The core structure of anthocyanins with two aromatic benzol rings (A and B rings) and a portion cyclized with oxygen (C ring).
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Figure 2. The main anthocyanins detected in root vegetables.
Figure 2. The main anthocyanins detected in root vegetables.
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Figure 3. The main carotenoids detected in root vegetables.
Figure 3. The main carotenoids detected in root vegetables.
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Figure 4. The main betalains detected in root vegetables.
Figure 4. The main betalains detected in root vegetables.
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Table
Table 1. The main pigments isolated in various root vegetables.
Table 1. The main pigments isolated in various root vegetables.
SpeciesEdible PartColorClass of CompoundsCompoundsReferences
Potato (Solanum tuberosum L.) Tuber (stem tuber)Purple Petunidin derivativesPetunidin-3-p-coumaroylrutinoside-5-glucoside,
petunidin-2-p-coumarylrutinoside-5-glucoside		[21,22,23,24]
RedPelargonidin, delphinidin, cyanidin, peonidin, and malvidin acyl-glycoside derivativesPelargonidin-3-p-coumaroylrutinoside-5-glucoside[21,23]
Purple/red CarotenoidsNeoxanthin, violaxanthin[25]
Yellow CarotenoidsAntheraxanthin[25]
Sweet potato (Ipomoea batatas L. Lam.)Tuberous root (root tuber)Purple Acylated anthocyaninsCyanidin, peonidin, and pelargonidin derivatives[26,27,28,29,30]
Carrot (Daucus carota L. ssp. sativus Hoffm.) Taproot (swollen hypocotyl and root)Purple or black Cyanidin derivativesAcylated cyanidin 3-xylosyl(glucosyl)galactosides with sinapic acid, ferulic acid, and coumaric acid; [31,32,33,34,35]
Vinylphenol and vinylguaiacol adducts of cyanidin derivatives[36]
Red and yellow CarotenoidsLycopene and β-carotene[37,38]
Beet root
(Beta vulgaris L.)		Root (swollen hypocotyl and root)Purple BetalainsBetacyanins[39,40]
Yellow BetalainsBetaxanthins[41]
Vulgaxanthin I and betanin[42]
Yam (Dioscurea sp. L.)Tuber
(stem tuber)		Purple Cyanidin, pelargonidin, and peonidin-type compounds; alatanins A–CCyanidin 3-hexoside acylated with two hydroxycinnamic acids, cyanidin 3-glycoside acylated with one hydroxycinnamic acid, cyanidin 3-glycoside acylated with one hydroxycinnamic acid, peonidin 3-glycoside acylated with one hydroxycinnamic acid, alatanin-C[43,44,45,46]
Yellow Carotenoidsβ-Carotene[47]
Onion (Allium cepa L.) Bulb (swollen basis of leaves) Purple Flavonols and acylated and non-acylated cyanidin glucosidesDihydroflavonol taxifolin and its 3-, 7-, and 4′-glucosides[48,49]
Radish (Raphanus sativus L.)Taproot (swollen root and hypocotyl)PurpleCyanidin glucosidesCyanidin 3-(glucosylacyl)acylsophoroside-5-diglucosides, cyanidin 3-sophoroside-5-diglucosides, cyanidin 3-sophoroside-5-glucosides, cyanidin 3-O-[2-O-(β-glucopyranosyl)-6-O-(trans-feruloyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside] cyanidin 3-[2-(glucosyl)-6-(cis-p-coumaroyl)-glucoside]-5-[6-(malonyl)-glucoside][50,51]
RedAnthocyaninsPelargonidin 3-sophoroside-5-glucoside, pelargonidin 3-[2-(glucosyl)-6-(trans-p-coumaroyl)-glucoside]-5-glucoside, pelargonidin 3-[2-(glucosyl)-6-(trans-feruloyl)-glucoside]-5-glucoside, pelargonidin 3-[2-(glucosyl)-6-(trans-p-coumaroyl)-glucoside]-5-(6-malonylglucoside), pelargonidin 3-[2-(glucosyl)-6-(trans-feruloyl)-glucoside]-5-(6-malonylglucoside), 3-O-[2-O-(b-d-glucopyranosyl)-6-O-(trans-caffeoyl)-b-d-glucopyr-anoside]-5-O-(6-O-malonyl-b-d-glucopyranoside), pelargonidin 3-O-[2-O-(b-d-glucopyranosyl)-6-O-(cis-p-cou-maroyl)-b-d-glucopyranoside]-5-O-(6-O-malonyl-b-d-glucopyranoside[52,53]
Kohlrabi (Brassica oleracea var. gongylodes)Swollen epicotylPurple Cyanidin and cyanidin glucosideCyanidin-3-diglucoside-5-glucoside, cyanidin-3-(sinapoyl)-diglucoside-5-glucoside, cyanidin 3-(feruloyl) (sinapoyl) diglucoside-5-glucoside[54,55,56,57]
Taro (Colocasia esculenta)CormPurple Cyanidin and pelargonidin glucosides[58]

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Petropoulos, S.A.; Sampaio, S.L.; Di Gioia, F.; Tzortzakis, N.; Rouphael, Y.; Kyriacou, M.C.; Ferreira, I. Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables. Antioxidants 2019, 8, 617. https://0-doi-org.brum.beds.ac.uk/10.3390/antiox8120617

AMA Style

Petropoulos SA, Sampaio SL, Di Gioia F, Tzortzakis N, Rouphael Y, Kyriacou MC, Ferreira I. Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables. Antioxidants. 2019; 8(12):617. https://0-doi-org.brum.beds.ac.uk/10.3390/antiox8120617

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Petropoulos, Spyridon A., Shirley L. Sampaio, Francesco Di Gioia, Nikos Tzortzakis, Youssef Rouphael, Marios C. Kyriacou, and Isabel Ferreira. 2019. "Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables" Antioxidants 8, no. 12: 617. https://0-doi-org.brum.beds.ac.uk/10.3390/antiox8120617

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