Two New Cycloartane Saponins from the Roots of Astragalus membranaceus

Two new cycloartane-type triterpenoid saponins were isolated from the roots of Astragalus membranaceus (FISCH.) BGE. (Leguminosae) cultivated in Kangwon province, Korea. These saponins were named astramembranosides A and B and were established to be cycloastragenol 6,25-di-O-beta-D-glucopyranoside (astramembranoside A) and cyclocanthogenin 3-O-beta-D-glucopyranosyl(1-->2)-beta-D-xylopyranoside (astramembranoside B) on the basis of chemical and spectral evidence. In addition, 12 known saponins were also isolated from the same materials. Although cycloastragenol 3-O-xyloside and agroastragalosides I and II have already been isolated from A. membranaceus adventitious roots, these three saponins together with brachyoside B and azukisaponin V methyl ester were isolated for the first time from this plant.