Bioactive saponins and glycosides. VII. On the hypoglycemic principles from the root cortex of Aralia elata Seem.: structure related hypoglycemic activity of oleanolic acid oligoglycoside.

The hypoglycemic component, elatoside E, was isolated from the root cortex of Aralia elata SEEM. (Araliaceae) together with elatoside F and eight known oleanolic acid glycosides, elatosides A and C, oleanolic acid 3-O-[alpha-L-arabinofuranosyl (1-->4)]-beta-D-glucopyranosiduronic acid, oleanolic acid 3-O-beta-D-glucopyranosiduronic acid, stipuleanosides R1 and R2, and chikusetsusaponins IV and IVa. The structures of elatosides E and F were determined on the basis of chemical and physicochemical evidence as oleanolic acid 3-O-[beta-D-xylopyranosyl (1-->2)][beta-D-glucopyranosyl (1-->3)]-alpha-L-arabinopyranoside and its 28-O-beta-D-glucopyranosyl ester, respectively. The hypoglycemic activity of oleanolic acid and nine oleanolic acid oligoglycosides from the root cortex of Aralia elata was determined by monitoring inhibition effect on the elevation of plasma glucose level by oral sucrose tolerance test in rats, and some structure-activity relationships of oleanolic acid glycoside were obtained.