INHIBITORY EFFECTS OF CUCURBITANE TRITERPENOIDS ON EPSTEIN-BARR-VIRUSACTIVATION AND 2-STAGE CARCINOGENESIS OF SKIN TUMORS

To search for possible anti-tumor-promoters, we carried out a primary screening of 21 cucurbitane triterpenoids using an in vitro assay syst em. Of these triterpenoids, scandenoside R6 (6), 23,24-dihydrocucurbit acin F (14), 25-acetyl-23,24-dihydrocucurbitacin F (15), -O-beta-D-glu copyranosyl-23,24-dihydrocucurbitacin F (17) and cucurbitacin F (18) e xhibited significant inhibitory effects on Epstein-Barr virus (EBV) ac tivation induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13- acetate (TPA). Further, compounds 14 and 17 exhibited remarkable anti- tumor-promotion effects on mouse skin tumor promotion in an in vivo tw o-stage carcinogenesis test.