Four new hydrolyzable tannins (phyllanthusiins A-D), a new polyphenol of related structure (phyllanthusiin E), and eight known polyphenols have been isolated from the leaves of Phyllanthus flexuosus. On the basis of the spectroscopic methods including ¹H-¹³C long-range two-dimensional nuclear magnetic resonance techniques, phyllanthusiins A (9), B (12) and C(14), were characterized as oxidative metabolites of geraniin, each having a different new acyl group biogenetically formed via an oxidative cleavage of the dehydrohexahydroxydiphenoyl group, on the ¹C₄ glucopyranose core. Phyllanthusiin D (15) was determined to be a condensate of geraniin with acetone, and phyllanthusiin E (16), was an oxidized congener of ellagic acid.