Cycloartane saponins from Astragalus peregrinus as modulators of lymphocyte proliferation - Verotta,L.; Guerrini,M.; El-Sebakhy,N.A.; Asaad,A.M.; Toaima,S.M.; Abou-Sheer,M.E.; Luo,Y.ing-De.; Pezzuto,J.M. (Fitoterapia, 2001)