Two new steroidal saponins from the biotransformation product of the rhizomes of Dioscorea nipponica

Abstract

Two new steroidal saponins, dioscins E (1) and F (2), along with nine known steroidal saponins, were isolated from the biotransformation product of the rhizomes of Dioscorea nipponica using Aspergillus oryzae. The structures of new compounds were established as 25(R)-spirost-5-en-21β-methyl-3β-ol-3-O-α- l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranoside (1) and (25R)-spirost-5-en-3β-ol-7-one 3-O-α- l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranoside (2) by detailed spectroscopic analyses including 1D and 2D NMR spectral data (¹H–¹H COSY, HSQC, and HMBC) and MS spectrometry.

Keywords:

• Dioscorea nipponica
• steroidal saponin
• dioscin E
• dioscin F
• Aspergillus oryzae

Acknowledgments

This work was financially supported by the Major Program of Municipal Natural Science Foundation of Beijing (7090001) and the NSFC-Union Foundation of Yunnan Province (U10132601). The authors are grateful to Miss Yan Xue and Mr He-Bing Chen in the National Center of Biomedical Analysis for the measurements of MS and NMR spectra.