STUDIES ON THE CONSTITUENTS OF ASTER-SCABER THUNB .3. STRUCTURES OF SCABEROSIDE-B7, SCABEROSIDE-B8 AND SCABEROSIDE-B9, MINOR OLEANOLIC ACID GLYCOSIDES ISOLATED FROM THE ROOT

Three new oleanolic acid 3,28-O-bisdesmosides, scaberosides B-7, B-8 and B-9, were isolated as minor saponins from the root of Aster scaber THUNB. (Compositae), and their structures were determined based on spectral and chemical evidence as follows. Scaberoside B-7 is 3-O-beta-D-glucopyranosyluronic acid oleanolic acid 28-{O-beta-D-apiofuranosyl-(1 --> 3)-[O-beta-D-xylopyranosyl-(1 --> 4)]-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl} ester, scaberoside B-8, 3-O-beta-D-glucopyranosyl oleanolic acid 28-[O-beta-D-xylopyranosyl-(1 --> 4)-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl] ester, and scaberoside B-9, 3-O-beta-D-glucopyranosyluronic acid oleanolic acid 28-{O-alpha-L-rhamnopyranosyl-(1 --> 2)-[O-beta-D-xylopyranosyl-(1 --> 6)]-beta-D-glucopyranosyl} ester. Scaberosides B-7 and B-9 were obtained as their methyl esters.