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 3,6,16,(24S),25-pentahydroxycycloartane (cyclocanthagenol), while caspicuside II owns (20R, 24S)-epoxy-3, 6,16, 25-tetrahydroxycycloartane (cycloastragenol). The chemical structures of these new cycloartane-type glycosides were established as 3-O--L-rhamnopyranosyl-16-O--D-xylopyranosyl-cyclocanthogenol and 3-O-[-D-xylopyranosyl(1 3)--D-glucopyranosyl]-6-O--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.