Crude Drugs from Aquatic Plants. IV. On the Constituents of Alismatis Rhizoma. (2). Stereostructures of Bioactive Sesquiterpenes, Alismol, Alismoxide, Orientalols A, B, and C, from Chinese Alismatis Rhizoma

Following the characterization of the triterpene constituents in Chinese Alismatis Rhizoma, we investigated the chemical structures of orientalols A, B, and C, isolated from the less polar fraction of the crude drug together with two known sesquiterpenes, alismol and alismoxide. On the basis of the chemical and physicochemical evidence, the structures of orientalols A, B, and C have been determined and those of alismol and alismoxide were revised.All five sesquiterpenes were found to show an inhibitory effect on the contraction of isolated bladder smooth muscle induced by carbachol.