Steroidal Saponins Isolated from an Australian Yam Dioscorea sp.

Abstract

Phytochemical characterization of the rhizome of an Australian species of Dioscorea, acquired as Dioscorea transversa R Br. but botanically identified as Dioscorea sp., led to the isolation of two steroidal saponins. The major constituent 1β-hydroxyprotogracillin (1) was previously unknown while the minor one was identified as protogracillin (2). The structure and stereochemistry of 1 were elucidated using a combination of MS studies, 1D and 2D NMR experiments and chemical degradation.