STUDIES ON INHIBITORS OF SKIN TUMOR PROMOTION .12. ROTENOIDS FROM AMORPHA-FRUTICOSA

As a part of screening studies for chemopreventive agents (anti-tumor-promoters), six North American plants belonging to the Amorpha genus were tested using an in vitro assay system. Of these plants, Amorpha fruticosa exhibited strong inhibitory effects on Epstein-Barr virus early antigen (EBA-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Also six rotenoids, amorphispironone [1], tephrosin [2], amorphigenin [3), 12a-hydroxyamorphigenin [4], 12a-hydroxydalpanol [5], and 6'-O-D-glucopyranosyldalpanol [6], were isolated from the leaves of A. fruticosa. Among these rotenoids, 1 and 2 exhibited remarkable inhibitory effects on EBV-EA activation induced by TPA. Further, 1 and 2 exhibited significant anti-tumor-promotion effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These investigations suggested that these rotenoids might be valuable anti-tumor-promoters.