Isolation and structure determination of steroidal saponin from Dioscorea zingiberensis

To study the chemical constituents of Dioscorea zingiberensis Wright, the EtOH extract of fresh rhizomes of D.zingiberensis was concentrated and partitioned further to produce petroleum ether-, ethylacetate-, n-butanol- and water-soluble fractions. The water-soluble fraction was subjected to column chromatography on macro resin AB-8, and the final products were obtained by repeated reversed-phase ODS and MCI gel CHP 20P column chromatography. Structures of compounds were elucidated by means of ¹H NMR, ¹³C NMR, ¹³⁵DEPT, HMQC, HMBC and TOCSY spectroscopic analyses. Five steroidal saponins were isolated, in which one new steroidal saponin was identified as (25R)-26-O-(β-D-glucopyranosyl)-furost-5-en-3β,22ξ,26-triol-4β-acetoxyl-3-O-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-(1→4)-［α-L-rhamnopyranosyl-(1→2)］-β-D-glucopyranoside (V). The compound V is a new compound, named as zingiberenin G. The compounds I, II and III were reported for the first time from D.zingiberensis Wright.