Antiproliferative constituents in the plant 8. Seeds of Rhynchosia volubilis

The MeOH extract of the seeds of Rhynchosia volubilis (Leguminosae) showed antiproliferative activity against human gastric adenocarcinoma [MK-1, 50% growth inhibition (GI(50)): 25 mug/ml], human uterus carcinoma (HeLa, GI(50 ): 30 mug/ml), and murine melanoma (B16F10, GI(50): 8 mug/ml) cells. Bioact ivity-guided fractionation resulted in the isolation of gallic acid methyle ster (1), gallic acid (2), 7-O-galloylcatechin (3), 1,6-di-O-galloylglucose (4), 1-O-galloylglucose (5), and trigalloylgallic acid (6), and their anti proliferative activity was estimated. All showed much stronger inhibition a gainst B16F10 cell growth than against HeLa and MK-1 cell growth. Compound 2 and its tetramer (6) with a free carboxyl group showed higher activity th an those which did not have a free carboxyl group. In relation to the galli c acid tetramer (6), two gallic acid dimers (ellagic acid and dehydrodigall ic acid) and trimers (tergallic acid dilactone and flavogallonic acid dilac tone) were tested for their activity, and compared with those of the isolat es.