Triterpene glycosides from Astragalus icmadophilus

Abstract

Six cycloartane-type triterpene glycosides were isolated from Astragalus icmadophilus along with two known cycloartane-type glycosides, five known oleanane-type triterpene glycosides and one known flavonol glycoside. The structures of the six compounds were established as 3-O-[alpha-L-arabinopyranosyl-(1-->2)-O-3-acetoxy-alpha-L-arabinopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane, 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-O-alpha-L-arabinopyranosyl-(1-->2)-O-beta-D-xylopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,24(S),25-pentahydroxy cycloartane, 3-O-[alpha-L-arabinopyranosyl-(1-->2)-O-3,4-diacetoxy-alpha-L-arabinopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane, 3-O-[alpha-L-arabinopyranosyl-(1-->2)-O-3-acetoxy-alpha-L-arabinopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,25-tetrahydroxy-20(R),24(S)-epoxycycloartane, 3-O-[alpha-L-arabinopyranosyl-(1-->2)-O-beta-D-xylopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,24alpha-tetrahydroxy-20(R),25-epoxycycloartane, 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-O-alpha-L-arabinopyranosyl-(1-->2)-O-beta-D-xylopyranosyl]-6-O-beta-D-glucopyranosyl-3beta,6alpha,16beta,24alpha-tetrahydroxy-20(R),25-epoxycycloartane by the extensive use of 1D- and 2D-NMR experiments along with ESIMS and HRMS analysis. The first four compounds are cyclocanthogenin and cycloastragenol glycosides, whereas the last two are based on cyclocephalogenin as aglycone, more unusual in the plant kingdom, so far reported only from Astragalus spp.