Steroidal Saponins from the Rhizomes of Dioscorea bulbifera and Their Cytotoxic Activity

Two new steroidal saponins, diosbulbisides D (1) and E (2), along with five known saponins (3-7) were isolated from the rhizomes of Dioscorea bulbifera L. Their structures were elucidated on the basis of spectral data. Compounds 6 and 7, two 3-O-trisaccharides of diosgenin spirostanes, showed moderate cytotoxic activity against human hepatocellular carcinoma cells, with IC50 values of 3.89 mu M and 7.47 mu M on SMMC7721, and 10.87 mu M and 19.10 mu M on Bel-7402 cell lines, respectively.