Cycloartane and oleanane saponins from Egyptian Astragalus spp. as modulators of lymphocyte proliferation

From the roots of Astragalus kahiricus DC., three known saponins, namely, astraversianin VI, astraversianin X, astragaloside VIII, and a new saponin were isolated and identified by spectral data. The structure of the latter was elucidated by spectral means and assigned as cycloastragenol 3-O-[beta-D-(2',3'-diacetyl, 4'-trans-2-butenoyl)-xylopyranosyl], 6-O-beta-D-xylopyranoside (kahiricoside 1). From the aerial parts of A. hamosus L., the known compounds azukisaponin V and peregrinoside I were isolated. As judged by in vitro tests, the saponins isolated from Astragalus spp. endemic to Egypt were not cytotoxic against a variety of human cancer cells. However, dose-related modulation of lymphocyte proliferation was observed, and structure-activity relationships are described.