Studies on teh Constitutents of Aster scaber THUNB.I. Structures of Scaberosides, Oleanolic Acid Glycosides Isolated from the Root

Abstract

Six oleanolic aicd glucuronide saponins, scaberosides B₁, B₂, B₃, B₄, B₅ and B₆ were isolated from the root of Aster scaber THUNB. (Compositae) as their methyl esters, and their structures were determined based on spectral and cheimical evidence. Scaberosides have a common prosapogenin structure, oleanolic acid 3-O-glucopyranosiduronic acid, and differ in the structures of the 28-O-linked sugar moieties.Scaberoside B₁ is a 28-[α-L-arabinopyranosyl] ester, scaberoside B₂, a 28-[β-D-xylopyranosyl] ester, scaberoside B₃, a 28-[O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester, and scaberoside B₄, a 28-[O-α-L-rhamnopyranosyl-(1→2)-β-D-xylopyranosyl] ester, scaberoside B₅, a 28-[O-β-D-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester, scaberoside B₆, a 28-{O-β-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2)-β-D-xylopyranosyl] ester of the prosapogenin.