Steroidal saponins from the flowers of Dioscorea bulbifera var. sativa.

Eleven steroidal saponins, dioscoreanosides A-K, along with five known congeners, were isolated from the flowers of Dioscorea bulbifera var. sativa. Their structures were established by extensive NMR experiments in conjunction with mass spectrometry. The isolated compounds were tested for cytotoxicity against urinary bladder carcinoma cells (ECV-304 cells). Our results revealed a moderate activity for spiroconazol A (15), pennogenin 3-O-α-l-rhamnopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranoside (12), and 26-O-ß-d-glucopyranosyl-(25R)-5-en-furost-3ß,17α,22α,26-tetraol-3-O-α-l-rhamnopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranoside (13).