Biol Pharm Bull. 2002 Sep; 25(9): 1241-3.

Antitumor-promoting constituents from Dioscorea bulbifera L. in JB6 mouse epidermal cells.

Gao H, Kuroyanagi M, Wu L, Kawahara N, Yasuno T, Nakamura Y.

Department of Traditional Chinese Medicines, Shengyang Pharmaceutical University, China.

An antitumor-promoting effect was found in the extracts/ingredients of a plant used as a traditional medicine in mainland China, using the neoplastic transformation assay of mouse epidermal JB6 cell lines. The ethyl acetate soluble fraction of 75% ethanol extract of the rhizomes of Dioscorea bulbifera L. showed an inhibitory effect against the tumor promotion of JB6 (Cl 22 and Cl 41) cells induced by a promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). Further investigation on the constituents of the EtOAc fraction from the rhizomes revealed the chemical structure to be kaempferol-3,5-dimethyl ether (1), caryatin (2), (+)-catechin (3), myricetin (4), quercetin-3-O-galactopyranoside (5), myricetin-3-O-galactopyranoside (6), myricetin-3-O-glucopyranoside (7) and diosbulbin B (8). Constituent antitumor-promoting activities were also examined in the same way. Compounds 1-7, characterized as flavonoids with the two hydroxyl groups at C-7 and C-4', showed the most potent inhibitory effect, but there seemed to be differences in the inhibitory effect between flavonol aglycones and flavonol glycosides. Compared with (-)-epicatechin, (+)-catechin exhibited much stronger inhibitory activity which suggested that chemical stereo structures of compounds affect the efficiency of inhibition. Compound 8 showed moderate activity. The constituents with antitumor-promoting activity from this plant are reported for the first time.