Triterpenoid saponins from Astragalus wiedemannianus Fischer

Abstract

Three cycloartane-type triterpene glycosides were isolated from Astragalus wiedemannianus together with eight known secondary metabolites namely cycloastragenol, cycloascauloside B, astragaloside IV, astragaloside VIII, brachyoside B, astragaloside II, astrachrysoside A, and astrasieversianin X. The structures were established mainly by a combination of 1D and 2D-NMR techniques as 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl]-25-O-beta-D-glucopyranosyl-20(R),24(S)-epoxy-3beta,6alpha,16beta,25-tetrahydroxycycloartane, 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl]-6-O-beta-D-glucopyranosyl-24-O-alpha-(4'-O-acetoxy)-L-arabinopyranosyl-16-O-acetoxy-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane, 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl]-6-O-beta-D-glucopyranosyl-24-O-alpha-L-arabinopyranosyl-16-O-acetoxy-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane. To the best of our knowledge, the presence of an arabinose moiety on the acyclic side chain of cycloartanes is reported for the first time.