Alisol C 23-acetate from the rhizome of Alisma orientale

Abstract

The title compound [systematic name: 11β-hydroxy-24,25-epoxy-3,16-oxo-protost-13 (17)-en-23-yl acetate], C32H48O6, a protostane-type triterpenoid, was isolated from the Chinese herbal medicine alismatis rhizoma (the rhizome of Alisma orientalis Juzep). The molecule contains four trans-fused rings, viz. three six-membered and one five-membered ring. Two of the six-membered rings have slightly distorted half-chair conformations, while the third exhibits a chair conformation. The five-membered ring is almost planar. An intermolecular O—H...O hydrogen bond between the hydroxy and epoxy groups and intra- and intermolecular C—H...O hydrogen bonds are observed.