Biol Res 43: 451-457, 2010

ARTICLES

 

Gastroprotective effect of the ethanolic extract of Parkia platycephala Benth. leaves against acute gastric lesion models in rodents

 

Hélio B Fernandes¹, Francilene V Silva¹, Flávia Franceli B Passos¹, Roosevelt D S Bezerra², Mariana H Chaves², Francisco A Oliveira¹ and Rita C Meneses Oliveira¹ *

Medicinal Plants Research Center¹, Department of Chemistry², Federal University of Piauí, Teresina, Pl, Brazil.

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ABSTRACT

Parkia platycephala Benth. (Leguminosae - Mimosoideae), popularly known as "visgueira", fava bean tree or "fava-de-bolota", is widely found in the Northern and Northeastern regions of Brazil. Its pods are used as cattle food supplement in the drought period. Compounds with a gastroprotective activity were obtained from the genus Parkia. Therefore, this study aimed at investigating the gastroprotective effect of the ethanolic extract of Parkia platycephala Benth. leaves (Pp-EtOH), as well as evaluating its possible mechanisms of action in experimental ulcer induction models. Lesions were induced by absolute ethanol, ethanol-HCl, ischemia-reperfusion and indomethacin in rodents. Pp-EtOH showed a protective effect in the lesion models (66, 48 and 52 %, respectively), but it was not able to protect gastric mucosa against indomethacin-induced lesions. Results show a possible participation of the NO-synthase pathway in the gastroprotection and an antioxidant activity, by the increase of the catalase activity. The participation of prostaglandins and potassium channels sensitive to ATP in the gastroprotective effect of Pp-EtOH seems less likely to occur. More comprehensive studies, therefore, should be carried out to elucidate the antiulcerative effects of this promising natural product against this gastrointestinal disorder.

Key terms: antioxidant, ethanol, gastroprotection, nitric oxide, Parkia platycephala, ulcer.

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1.       INTRODUCTION

Ulcer is a deep mucous lesion , with the destruction of the components of the epithelial and conjunctive tissues, including subepithelial myofibroblasts, smooth muscle cells, vessels and nerves [Milani and Calabro, 2001]. Ulcers are likely to result from different pathogenic mechanisms and, non-dependant on its etiology, are formed when an imbalance between the aggressive factors of the mucous membrane, endogenous (chloride acid and pepsin) or exogenous (non-steroidal anti-inflammatory, smoking and alcohol) and the gastric mucous membrane protective factors (mucus, bicarbonate, prostaglandins, blood flow, nitric acid) occur [Glavin and Szabo, 1992; Wallace and Granger, 1996],

Usually, antiulcerogenic compounds obtained from plants exert their effects by stimulating the protective factors of gastric mucosa due to increased synthesis of prostaglandins, by stimulating the secretion of mucus and bicarbonate, through inhibition of acid secretion by interacting with different receptors, or regulating enzymes or hormones involved in the secretory process (Borrelli and Izzo, 2000).

Parkia platycephala Benth. (Leguminosae - Mimosoideae), popularly known as "visgueira" or "fava-de-bolota", is an arboreal species found all over the Northern and Northeastern part of Brazil, and its pods are widely used in cattle breeding as food [Alves, 2004; Nascimento and Machado, 2007].

There are no studies or popular indications proving the activity of this species against gastrointestinal disorders. However, antioxidant and gastroprotective compounds have been verified in some species of the genus Parkia: triterpenes β-amirin and lupeol have been isolated from the Parkia pendula, and campesterol, stigmasterol, β-sitosterol, ferulic acid, catechin and epicatechin have been isolated from Parkia biglobosa [Tringali, Spatafora and Longo, 2000; Akintayo, 2004]. Therefore, the objective of this work is to investigate the presence of gastroprotective activity in the ethanolic extract of Parkia platycephala Benth. (Pp-EtOH) leaves and evaluate the possible action mechanisms.

To study Pp-EtOH-induced gastroprotection, we used ethanol and HCl/ethanol models of acute gastric lesions. These models allowed us to assess whether the studied extract stimulates or maintains the resistance of the gastric mucosa against the lesions produced by exogenous substances, a mechanism which can be attributed to many factors present in the stomach, known as protective factors of gastric mucosa (Wallace, 2001). Lesions caused by ethanol, HCl/ethanol or ischemia-reperfusion injuries are hemorrhagic, resulting from intense production of free radicals causing damage to gastric epithelial cells. This damage leads to constriction of gastric mucosa veins and arteries, producing congestión, inflammation and tissue injury (Repetto and Liesuy, 2002). As well, ischemia weakens gastric mucosa resistance to acid and increases its susceptibility to damage. After reperfusion, ROS promote lipid peroxidation, which results, in combination with gastric acid secretion, in damage to the gastric mucosa (Brzozowski et al, 2000).

One of the most important components of mucosal defense is the blood flow response to irritants. Endothelial cells from these beds produce potent vasodilators, such as nitric oxide (NO) and prostacyclin (PGI2), which protect the gastric mucosa. Sugita (2003) reports the cytoprotective effects of nitric oxide (NO) on intestinal lesions caused by ethanol. In order to assess nitric oxide cytoprotective effect in gastric injury, it is used a NO-synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). Nitric oxide (NO) has been recognized as a key mediator in gastric defense mechanisms, because it stimulates mucus production, inhibits neutrophil adherence to endothelial cells and especially increases blood flow to the gastric mucosa (Coruzzi et al, 2000).

The ATP dependent potassium channels (K_ATP) belong to a large family of membrane proteins and are activated by ligands. In the vascular system, they are implicated in vascular smooth muscle relaxation, playing a role in blood pressure control. The literature shows that K_ATP channels are involved in a variety of pathophysiological functions in the stomach, for example, regulation of blood flow and gastric acid secretion (Toroud et al., 1999).

The ulcer induced by NSAIDs, such as indomethacin is a process that involves múltiple mechanisms. Indomethacin promotes depletion of cytoprotective prostaglandins in gastric mucosa by inhibiting the enzyme cyclooxygenase, microcirculatory disturbances with reduced blood flow, gastric hypermotility, topical irritation and interference in tissue repair (Filaretova et al., 2002). In this model there is an increased vascular permeability and neutrophils infiltration in the development of lesions (Jainu and Devi, 2006).

2.       MATERIALS AND METHODS

2.1.      Animals

All experiments were performed on male Swiss mice (20-30 g) and Wistar rats (180-200 g) with access to food and water, in a 12-hour day-night cycle at 24 ± 2 °C obtained from the Vivarium-NPPM, UFPI, Teresina city, Piauí State, Brazil. Before each experiment, the animals fasted for 24 hours with free access to water. The UFPI Research Ethics Committee approved all of the applied protocols (23/08).

2.2.       Vegetal material and extract preparation

Leaves of plants were collected in Timón, Maranhao State, and identified with the help of the Biology Department. Voucher specimens have been deposited at the herbarium Graziela Barroso - UFPI, Teresina - Piauí State (Brazil), number TEPB - 15.553. Air-dried and powdered leaves (2.263.2 g) were extracted by EtOH 95% and macerated at room temperature. The solvent was evaporated and the extract concentrated (Pp-EtOH), resulting in 547 g (24.2 % yield).

2.3.       Study of potential toxic effects of Parkia platycephala in vivo and in vitro

To determine acute toxicity, we used the method described by Miller and Tainter [1944]. Male and female mice (n = 10) received Pp-EtOH at a single dose of 2000 mg/kg and the control group received saline (10 mL/kg) by gavage. Mortality, body weight and behavioral screening were recorded daily for 14 days after the treatment. To assess cellular toxicity in rat erythrocytes, the method proposed by Rangel et al. [1997] was used with modifications. The rat blood was collected and added to a CaCl₂ 10 mM saline solution. The erythrocytes were washed twice by centrifugation at 3000 rpm/3min. The last centrifugation sediment was resuspended in saline and bubbled with carbogen air. Crescent concentrations of Pp-EtOH (1-1000 µg/ml) were added to test tubes in triplícate. In positive control 100 µL of Tritón X-100 1% (100% hemolysis) was added. Some 100 µL of washed erythrocytes was added to each test tube and the volume completed at 0.5 mL for 1 hour with constant shaking. The samples were then centrifuged (3000 rpm/3min) and the hemolysis was assayed on a spectrophotometer at 540 nm.

2.4.       Study of the anti-ulcer action of P. platycephala in the ethanol induced ulcer model

Mice were pretreated orally with vehicle (NaCl 0.9 %), positive control (carbenoxolone 100 mg/kg) or Pp-EtOH (62.5, 125 or 250 mg/kg). After one hour, they were treated by absolute ethanol (0.2 mL/animal, p.o.) according to Robert et al. [1979]. After 30 minutes, the animals were killed and their stomachs removed and opened along the greater curvature to determine the lesion area (mm²). The lesion area was calculated by the following formula: lesion area (%) = lesion area (mm²) x 100/total area (mm²)

2.5.       Role of nitric oxide and K_ATP channels in the gastroprotective effect of Pp-EtOH in the ethanol induced ulcer model

Mice were pretreated with vehicle, positive control (L-arginine, 600 mg/kg, i.p.) and Pp-EtOH (250 mg/kg, p.o.) alone, or in their combinations with L-NAME (20 mg/kg, i.p.) prior to induction of gastric damage with absolute ethanol. While Pp-EtOH was administered 1 hour before, L-NAME and L-arginine were given 30 min prior to ethanol [Olinda et. al, 2008].

In another study, mice were pretreated with vehicle, positive control diazoxide (3 mg/kg, i.p.), Pp-EtOH (250 mg/kg, p.o.) alone, or in their combinations with glibenclamide (5 mg/kg, i.p.) prior to the oral administration of absolute ethanol. Pp-EtOH was given 1 h before, whereas diazoxide was administered 30 min prior to ethanol or glibenclamide. Glibenclamide was administered 30 min before Pp-EtOH [Olinda et. al, 2008],

2.6.       Study of the anti-ulcer action of P. platycephala in the HCl/ ethanol induced ulcer model

Groups of mice were pretreated orally with vehicle, carbenoxolone (100 mg/kg) or Pp-EtOH (62.5, 125 or 250 mg/kg). After one hour, the animals were treated with an HCl/ethanol solution, according to Mizui and Doteuchi [1983]. Past 30 minutes, the mice were sacrificed and their stomachs removed and opened along the greater curvature to determine the lesion area (mm²).

2.7.       Study of the anti-ulcer action of P. platycephala in the ischemia-reperfusion induced ulcer model

The method proposed by Yoshikawa [1989] was used. Rats were treated with vehicle, positive control (N-acetyl cysteine (NAC), 750 mg/kg, i.p.) or Pp-EtOH (250 mg/kg p.o.). After one hour, ischemia-reperfusion erosions were produced in rats. Briefly, under tiopenthal anesthesia (50 mg/kg, i.p.), the celiac artery was clamped with a small device for 30 minutes. After this, the clamping device was removed to obtain the reperfusion. After one hour of reperfusion, the animals were killed and their stomachs removed and opened along the greater curvature to determine the lesion area (mm²).

2.8.       Study of the anti-ulcer action of P. platycephala in the indomethacin induced ulcer model

In this model, rats were treated orally with vehicle, positive control (cimetidine 100 mg/kg) and Pp-EtOH (250 mg/kg). One hour after this treatment, indomethacin, suspended in 5% bicarbonate water, was administered in a dose of 30 mg/ kg s.c. (0.1 mL/100 g) [Bhargava, Gupta and Tangri, 1973]. After 6 hours of indomethacin treatment, the stomachs of the animals were removed, rinsed with formalin 1% and studied according to the standard procedure [Szabo et al., 1985].

2.9.       Catalase activity on the anti-ulcer action of P. platycephala in the ethanol induced ulcer model

Stomachs previously submitted to absolute ethanol [Robert et al., 1979] were used to assess the role of catalase (CAT) in Pp-EtOH-induced mucosa protection. The determination of CAT activity present in the gastric mucosa was assayed by a modification of the spectrophotometric method of Beers and Sizer [1952]. Mice were pretreated with vehicle, positive control (N-acetyl cysteine (NAC), 750 mg/kg i.p.) or Pp-EtOH (250 mg/kg, p.o.). They were then treated with absolute ethanol (0.2 mL/animal, p.o.) [Robert et al.,1979]. The animals were killed and their stomachs removed and put in a homogenate ice-cold buffer (KH2PO4/K2HPO4, pH=7,4) and then centrifuged at 3000 rpm for 15 minutes. An approximately 0.05 M solution of hydrogen peroxide substrate was prepared with 0.05 M KH₂P0₄ buffer, pH 7.4 in distilled water. Aliquots of 0.1 mi of supernatant were added into 1.9 mi of substrate solution and the disappearance of hydrogen peroxide was followed spectrophotometrically at 240 nm.

2.10.       Statistical analysis

The results are presented as the mean ± S.E.M. Statistical analysis was carried out using the one-way analysis of variance (ANOVA) followed by Tukey post hoc test for múltiple comparisons. P-values less than 0.05 (p<0.05) were considered as indicative of statistical significance.

3.       RESULTS

3.1.       Study of potential toxic effects of Parkia platycephala in vivo and in vitro

The investigation of the potential toxic effects of extracts obtained from leaves of Parkia platycephala Benth. aimed at establishing a safe and effective dose in the investigation of gastroprotective activity of the extract in models of acute gastric lesions.

The ethanolic extract obtained from the leaves of Parkia platycephala Benth. (Pp-EtOH) in the dosage of 2 g/kg, orally, did not demónstrate any sign of evident toxicity and it did not cause the deaths of the animals, within 72 hours. In the evaluation of the cytotoxicity in rat erythrocytes, lytic activity was not evidenced up to the concentration of 100 µg/mL of Pp-EtOH. In the greater concentration used, hemolysis in the erythrocytes was not greater than 5%, as compared to Triton-X-100 (100%). In the group of saline, as expected, there was no hemolysis (0 %), assuring a good margin of safety for the extract.

3.2.       Study of the anti-ulcer action of P. platycephala in the ethanol induced ulcer model

It is known that the damage caused by ethanol in the gastric mucosa result from disturbances in microcirculation, ischemia and the appearance of free radicals, release of endothelin, degranulation of mast cells, inhibition of prostaglandin synthesis and consequent reduction in mucus production (Samonina et al, 2004). According to the results, Pp-EtOH (62.5, 125 or 250 mg/kg, p.o.) reduced the lesion area in the gastric mucous membrane dose-dependently (62.2 ± 4.6; 35.1 ± 7.0 and 22.3 ± 8.7 mm², respectively). Pp-EtOH in the dosage of 250 mg/kg provided greater protection, compared to the control group (65.5 ± 3.8 control vs. 22.3 ±8.7   mm² (Pp-EtOH), corresponding to 66% of lesion inhibition. (Fig. 1). The positive control did not show significant difference between Pp-EtOH 250 mg/kg (19.3 ±3.8  vs 22.3 ± 8.7 mm², respectively) with inhibition of 70.22

3.3.       Role of nitric oxide and K_ATP channels on the gastroprotective effect of Pp-EtOH in the ethanol induced ulcer model

In mechanistic studies, separate experiments were realized to examine the role of nitric oxide and K⁺_ATP channel activation on the gastroprotective effect of P. platycephala (Pp-EtOH), using appropriate agonists (Olinda et al., 2008).

The treatment with NG-nitro-L-arginine methyl ester (L-NAME) an inhibitor of nitric oxide synthase (20 mg/kg, i.p.) inhibited the protection of the mucous membrane offered by Pp-EtOH (250 mg/kg), increasing the lesion area significantly (22.4 ± 8.7 to 70.4 ± 11.7 mm²), with no significant difference in the control group (67.2 ± 6.1 mm²), as was observed in positive control, L-Arginine 600 mg/kg (8.9 ± 1.50 mm² to L-Arginine vs. 29.4 ± 2.9 mm² to L-Arginine + L-NAME), suggesting the participation of this method in the gastroprotection of this extract (Fig. 2).

After the treatment with glibenclamide, a K⁺_ATP channel blocker (5 mg/kg i.p.), Pp-EtOH (250 mg/kg) reduced ethanol-induced lesions, without significant difference comparing to the non-blocked group (27.9 ± 5.7 vs. 22.4 ± 8.7 mm², respectively). In positive control (diazoxide 3 mg/kg) after the blockage with glibenclamide, an increase in gastric lesions (12.5 ± 1.6 to 22.6 ± 1.0 mm²) was observed, suggesting that these channels are probably not involved in the gastric protection evidenced by Pp-EtOH (Fig. 3).

3.4.       Study of the anti-ulcer action of P. platycephala in the HCl/ethanol induced ulcer model

The presence of HC1 in ethanol solution accelerates the progress of ulcerogenesis and enhances gastric injury (Sing et al., 2008). In this model, Pp-EtOH only promoted a significant level of gastroprotective activity with the dose of 250 mg/kg (50.3 ± 3.5 mm²) in comparison to the control group (97.5 ± 12.8 mm²), corresponding to a 48% inhibition of the lesion area (Fig. 4). Carbenoxolone, the positive control, has a significant reduction in lesion area compared to the control group (35.35 ± 7.89 vs 97.84 ± 12.97 mm², respectively).

3.5.       Study of the anti-ulcer action of P. platycephala in the ischemia-reperfusion induced ulcer model

Ischemia-reperfusion (I/R) induces gastric injury as a result of excessive formation of reactive oxygen species (ROS), neutrophils infiltration and gastric microvascular dysfunction (Derin et al., 2006). The Pp-EtOH extract (250 mg/kg, p.o.) reduced the ischemia-reperfusion-induced lesion area (40.9 ± 9.7 mm²) compared to the control group (89.6 ± 8.2 mm²), corresponding to a 52% inhibition. The positive NAC control (750 mg/kg, i.p.) was also effective in reducing the lesion areas (42.8 ± 7.6 mm²) (Fig. 5).

3.6.       Study of the anti-ulcer action of P. platycephala in the indomethacin induced ulcer model

Indomethacin, a potent inhibitor of prostaglandin production, acts on gastric mucosa to promote an increase in acid production and decrease the formation of cytoprotective mucus, which may lead to ulcer formation (Walace and Devchand 2005). In this protocol, the indomethacin-induced gastric ulcers in the control group reached the values 5.2 ± 0.6. Pp-EtOH (250 mg/kg, p.o.) was not able to protect the gastric mucous membrane from the ulcer lesions (5.4 ± 0.6). Cimetidine (100 mg/kg, p.o.), the positive control for the test, reduced the values of the lesions (0.7 ± 0.1) (Fig. 6).

3.7.      Anti-oxidant catalase activity of P. platycephala in the ethanol induced ulcer model

The release of oxygen-derived free radicals (ROS) has drawn attention as a possible pathogenic factor of gastric mucosal injury associated with ethanol consumption. Preventive antioxidants, such as catalase (CAT) and others, are the first line of defense against ROS (Alimi et al., 2010). Therefore, in the present study the activity of CAT in rat stomach tissue was studied to explore the effects of Pp-EtOH on oxidative damage. The Pp-EtOH extract (250 mg/kg) increased the activity of this enzyme significantly, in comparison to the control group (205.2 ± 17.3 vs. 67.9 ± 6.5, respectively). The positive control (NAC, 750 mg/kg, i.p.) also increased catalase activity significantly to mean values similarly to the non-treated (SHAM) group (189.1 ± 17.8 vs. 162.7 ± 13.0 mM/min.100 mg of tissue, respectively) as shown in Fig. 7.

4.      DISCUSSION

In the current study, the main findings reveal that the ethanolic extract obtained from the leaves of Parkia platycephala Benth. (Pp-EtOH) presents gastroprotective activity in acute models of gastric lesions in mice and rats.

The absence of acute toxicity in mice and cytotoxicity in rat erythrocytes for the Pp-EtOH extract ensure a good margin of safety for the doses of this extract in the experimental protocols of gastric lesions, as well as in the models used for the elucidation of the action mechanism.

Ethanol and acidified ethanol are among the most widely used agents in experimental models for the evaluation of the antiulcerative activity in mice [Robert et al., 1979; Mizui and Douteuchi, 1983].

Ethanol necroses the superficial cells of the gastric mucous membrane by precipitation of the cytoplasmatic components, interrupting the function of the cell mucous membranes, with the participation of vasoactive mediators released, such as leukotrienes C₄ (LTC₄) and histamine [Jamal et al., 2006]. These mediators cause the submucous membranes to constrict with a subsequent blood flow stasis of the microcirculation in the mucous membrane, with the formation of edema, which may contribute to the increase of lesions in this model [Konturek et al., 1988; Wallace, 2001], Ethanol induces the solubilization of the mucous constituents in the stomach, increases the flow of sodium and potassium in the lumen, increases the pepsin released, and decreases the tissue levéis of DNA, RNA and proteins, leaving the mucous membrane unprotected, leading to an injury in the tissue [Robert et al., 1979]. HC1 further deepens the necrosis and increase tissue injury [Singh et al., 2010]. In the results obtained, it was observed that Pp-EtOH reduced the lesions caused by these agents, suggesting the presence of gastroprotective activity in this extract.

Anti-inflammatory drugs, such as indomethacin, injure the gastric mucous membrane through the inhibition of the gastric cyclooxygenase enzyme, resulting in the decrease of the production of prostaglandins [Wallace et al., 2000], Prostaglandins, such as E₂ and prostacyclins, act on the synthesis of mucus and bicarbonate, on the regulation of the acid secretion and on the blood flow of the gastric mucous membrane, and its inhibition critically compromises the gastric cytoprotection [Whittle, Oren-Wolman and Guth, 1985]. The increase of the production of these prostanoids provides greater resistance of the gastric mucous membrane against several agents, such as anti-inflammatory drugs [Wallace, 2001; Arun and Asha, 2008; Nguelefack et al., 2008]. According to the results obtained by the extract in the indomethacin-induced lesion model (Fig. 6), the prostaglandins are not likely to participate in the gastroprotection of Pp-EtOH, since this extract could not reduce the gastric lesion area in relation to the control.

The nitric oxide (NO), produced by the NO- synthase pathway, has been recognized as a fundamental mediator in the gastric defense mechanisms because it stimulates mucus production, inhibits the adherence of neutrophiles to the endothelial cells, and especially because it increases the blood flow of the gastric mucous membrane [Coruzzi et al., 2000; Olinda et al., 2008]. The inhibition of the production of NO by the use of L-NAME inferieres in the gastroprotective activity of several vegetal extracts [Ferreira et al., 2008; Gomes et al., 2009]. In this study, the pre-treatment with L-NAME, an NO-synthase inhibitor, reversed the gastroprotective effect of Pp-EtOH (Fig. 2). Since the NO-synthase pathway is important for the development of the protective activity, it is suggested that the NO may be mediating the gastroprotection of this extract.

Studies have reported that the activation of potassium channels sensitive to ATP (K⁺ _ATP) reduces gastric lesions and that the use of glibenclamide, a blocker of these channels, intensifies them. The activation of these channels may occur in several ways, such as through the action of NO [Murphy and Brayden, 1995; Chandranath, Bastaki and Singh, 2002], Treatment with glibenclamide did not inhibit the gastroprotective effect of Pp-EtOH, and the participation of K+ _ATP in this effect is less likely to occur.

Gazzieri [2007] has demonstrated that ethanol increases the production of reactive oxygen species (ROS). In ischemia and reperfusion experiments, lesions appear in the cells of the gastric mucous membrane due to the formation of ROS [Ueda, Yoshikawa and Takahashi, 1989]. Among the most common ROS are the superoxide and the hydroxyl, responsible for lipoid peroxidation and chemotaxis of inflammatory cells with injuries [Yu et al., 2002; Ribeiro and Yoshida, 2005]. The cell is provided with several antioxidant mechanisms, such as the superoxide dismutase enzymes (SOD), catalase (CAT), and glutathione peroxidase, which detoxifies these ROS and reduces oxidative damage [Bafna and Balaraman, 2004; Alimi et al., 2010]. Pp-EtOH reduced the ischemia-reperfusion-induced lesions with an increase of catalase activity, showing an antioxidant effect, suggesting its efficacy in preventing the damages caused by ROS.

Preliminary phytochemical studies have reported the presence of a high percentage of phenolic compounds in the extract (Pp-EtOH) from leaves of Parkia platycephala Benth [Bezerra, Carvalho and Chaves, 2009]. Phenolic compounds are special metabolites that have significant antioxidant activity (Chun et al., 2005). It is reported in the literature that phenolic compounds participate significantly in the gastroprotection of a great number of vegetal extracts [Almeida et al., 2002]. Based on these facts, these compounds, also identified in the Pp-EtOH extract, may be part of the gastroprotective activity evidenced.

Pp-EtOH showed gastroprotective effects in the ethanol-and ethanol-HCl- and ischemia-reperfusion-induced gastric ulcer models, possibly due to the participation of the NO-synthase pathway and an increase of the catalase enzyme activity, with no apparent toxic effects. More comprehensive studies are necessary to explain the mechanisms of action and safety profile of this extract, aimed at the development of new anti-ulcerative therapies derived from this product.

In conclusion , the results of this study indicate that Pp-EtOH shows gastroprotective activity against gastric damage induced by ethanol and ethanol-HCl, but not by indomethacin, which is possibly mediated, in part, by the nitric oxide reléase, although there is no involvement of the activation of K⁺_ATP or of prostaglandins. This extract also exhibits protection against lesions by ischemia-reperfusion and an antioxidant effect, in part, by an increase in catalase activity. Further studies are necessary to elucidate the mechanisms of action and the safety profile of this extract.

 

ACKNOWLEDGEMENTS

We gratefully acknowledge financial support received from the Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq/MCT/Projeto Universal (03/2009), Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior (CAPES)/Brazil.

The authors thank Edison S. Ferreira Filho and Joao Batista for translation of the text to English.

 

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Received: March 15, 2010. In revised form: October 26, 2010. Accepted: November 9, 2010.

* Corresponding author: Rita de Cássia Meneses Oliveira, Medicinal Plants Research Center, Federal University of Piauí, Minister Petrônio Portela Campus, 64049-550 Teresina-PI, Brazil. Phone: +55 86 3215 58 72, E-mail: menesesoliveira@gmail.com, ritameneses@ufpi.br