Bioactive Saponins and Glycosides. VI. Elatosides A and B, Potent Inhibitors of Ethanol Absorption, from the Bark of Aralia elata Seem. (Araliaceae): The Structure-Requirement in Oleanolic Acid Glucuronide-Saponins for the Inhibitory Activity

摘要

Potent inhibitors of ethanol absorption, elatosides A and B, were isolated from the bark of Aralia elata Seem, through bioassay-guided separation together with elatosides C and D and four known oleanolic acid glucuronide-saponins, spinasaponin A, spinasaponin A 28-0-glucoside, and stipuleanosides Rj and R2. The structures of elatosides A, B, C, and D were determined on the basis of chemical and physicochemical evidence as oleanolic acid 3-0-{[/f-D-xylopyranosyl (l->2)] [/J-D-galactopyranosyl (l-?3)]}-/?-D-glucopyranosiduronic acid, oleanolic acid 3-0-{[/?-D-galactopyranosyI (l-?2)] [/J-D-galactopyranosyl (l-+3)]}-/J-D-glucopyranosiduronic acid, and their 28-O-glucopyranosyl esters, respectively.The inhibitory effect of various oleanolic acid 3, 28-O-bisdesmosides, oleanolic acid 3-O-monodesmosides, and oleanolic acid on ethanol absorption was examined and it was found that the 3-0-glucuronide moiety and the 28-carboxyl group in oleanolic acid glucuronide-saponin were required to exert the inhibitory activity.