Studies on the constituents of Aster scaber Thunb. V. Structures of six new echinocystic acid glycosides isolated from the herb.

Abstract

Six new echinocystic acid 3,28-O-bisdesmosides, scaberosides Hc2, Hd, Hf, Hg, Hh and Hi, were isolated as their methyl esters from the ground part of Aster scaber THUNB. (Compositae), and their structures were determined based on spectral and chemical evidence as follows. Scaberoside Hc2 is 3-O-[O-beta-D-xylopyranosyl-(1-->3)-beta-D-glucopyranosiduronic acid] echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->3)-O-beta-D- xylopyranosyl-(1-->4)-O-alpha-L-rhamnopyranosyl-(1-->2)-[O-alpha-L- rhamnopyransoyl-(1-->3)]-beta-D-xylopyranosyl)ester, scaberoside Hd, 3-O-[O-beta-D-xylopyranosyl-(1-->3)-beta-D-glucopyranosiduronic acid] echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->3)-O-beta-D- xylopyranosyl-(1-->3)-[O-beta-D-xylopyranosyl-(1-->4)]-O-alpha-L- rhamnopyranosyl-(1-->2)-[O-alpha-L-rhamnopyranosyl-(1-->3)]-beta-D- xylopyranosyl) ester, scaberoside Hf, 3-O-[O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucopyranosiduronic acid] echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->4)-O-alpha-L- rhamnopyranosyl-(1-->2)-[O-alpha-L-rhamnopyranosyl-(1-->3)]-beta-D- xylopyranosyl) ester, scaberoside Hg, 3-O-[O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucopyranosiduronic acid] echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->3)-O-beta-D- xylopyranosyl-(1-->4)-O-alpha-L-rhamnopyranosyl-(1-->2)-[O-alpha-L- rhamnopyranosyl-(1-->3)]-beta-D-xylopyranosyl) ester, scaberoside Hh, 3-O-(O-beta-D-galactopyranosyl-(1-->2)-[O-beta-D-xylopyranosyl-(1-->3)]- beta-D-glucopyranosiduronic acid) echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->3)-O-beta-D- xylopyranosyl-(1-->4)-O-alpha-L-rhamnopyranosyl-(1-->2)-[O-alpha-L- rhamnopyranosyl-(1-->3)]-beta-D-xylopyranosyl) ester and scaberoside Hi, 3-O-[O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucopyranosiduronic acid] echinocystic acid 28-(O-beta-D-xylopyranosyl-(1-->3)-O-beta-D-xylopyranosyl-(1-->3)-[O-bet a-D- xylopyranosyl-(1-->4)]-O-alpha-L-rhamnopyranosyl-(1-->2)-[O-alpha-L- rhamnopyranosyl-(1-->3)]-beta-D-xylopyranosyl) ester.