Structures of new friedelane-type triterpenes and eudesmane-type sesquiterpene and aldose reductase inhibitors from Salacia chinensis.

Three new friedelane-type triterpenes named salasones A (1), B (2), and C (3), a new norfriedelane-type triterpene, salaquinone A (4), and a new acylated eudesmane-type sesquiterpene, salasol A (5), were isolated from the 80% aqueous methanolic extract of the stems of Salacia chinensis collected in Thailand. Their stereostructures were elucidated on the basis of chemical and physicochemical evidence. In addition, six constituents, 3beta,22beta-dihydroxyolean-12-en-29-oic acid, tingenone, tingenine B, regeol A, triptocalline A, and mangiferin, were found to show an inhibitory effect on rat lens aldose reductase.