ANTI-TUMOR-PROMOTING ACTIVITIES OF EUGLOBALS FROM EUCALYPTUS PLANTS

To search for possible anti-tumor-promoters (chemopreventive agents), we carried out a primary screening of 21 euglobals (acylphloroglucinol -monoterpene or -sesquiterpene structures) isolated from the juvenile leaves of five species of Eucalyptus plants using an in vitro synergis tic assay system. Of these compounds, euglobal-G1- -G5 (1-5), -Am-2 (1 5) and -III (16) exhibited significant inhibitory effects on Epstein-B arr virus (EBV) activation induced by the tumor promoter, 12-O-tetrade canoylphorbol-13-acetate (TPA). Furthermore, the effects of compounds 1 and 16 on the cell cycle of Raji cells were also examined by a how c ytometer, and both compounds 1 and 16 exhibited strong inhibition on t he effect of the cell cycle induced by TPA. These two euglobals (1 and 16) exhibited remarkable anti-tumor-promoting effects on mouse skin t umor promotion in an in vivo two-stage carcinogenesis test.