Cycloartane-type glycosides from the roots of Astragalus caspicus Bieb.

Two new cycloartane-type glycosides, caspicuside I and caspicuside II, were isolated along with two known saponins, cycloastragenol and astragaloside IV, from the roots of Astragalus caspicus. As the aglycon group, caspicuside I possesses 3beta,6alpha,16beta,(24S),25-pentahydroxycycloartane (cyclocanthagenol), while caspicuside II owns (20R, 24S)-epoxy-3beta, 6alpha,16beta, 25-tetrahydroxycycloartane (cycloastragenol). The chemical structures of these new cycloartane-type glycosides were established as 3-O-alpha-L-rhamnopyranosyl-16-O-beta-D-xylopyranosyl-cyclocanthogenol and 3-O-[beta-D-xylopyranosyl(1 --> 3)-beta-D-glucopyranosyl]-6-O-beta-xylopyranosyl-cycloastragenol, respectively. These findings add to a growing body of literature demonstrating the high variation of cycloartane-type triterpene glycosides in different species of Astragalus.