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.

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-O-glucoside, and stipuleanosides R1 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-O-¿[beta-D-xylopyranosyl (1-->2)] [beta-D-galactopyranosyl (1-->3)]¿-beta-D-glucopyranosiduronic acid, oleanolic acid 3-O-¿[beta-D-galactopyranosyl (1-->2)] [beta-D-galactopyranosyl (1-->3)]¿-beta-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-O-glucuronide moiety and the 28-carboxyl group in oleanolic acid glucuronide-saponin were required to exert the inhibitory activity.