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Chemopreventive Effects of Brazilian Medicinal Plant, Tabebuia avellanedae Extract against Microbiological Tumor Promoter, Teleocidin
In our continuous search for chemopreventive active constituent from natural sourse material, medicinal plant, Tabebuia avellanedae (TA) have been screened using the in vitro synergestic assay indicated by inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) by TPA. In this assay, TA and including naphthoquinone comounds NQ801 exhibited the potential inhibitory effects on EBV-EA activation without cytotoxicity on Raji cells.In our experiments, the inhibitory effects of TA and NQ801 were same activity that of carotenoids, which is a known anti-tumor promoting agents On the basis of the results by in vitro assay, the inhibitory effects of these compounds were investigated in two-stage carcinogensis test of mouse skin tumor using DMBA as an initiator and teleocidin as a another type potential promoter Teleocidin isolated from Streptomyces mediocidicus and also exerts a broad spectrum of biological effects in addition to tumor promoting activity in vivo with potencies equivalent to those of TPA. In the present work, TA and NQ801 was topically administred for 1h before the each promotion treatment, using teleocidin and showed 50% inhibited mouse skin caricinogenesis promoted by indole alkaloids type compounds. These effects were essentially identical with those produced by TPA and we thought that these compounds also might be as potential as TPA in term of anti-tumor-promoting activity on mouse skin against teleocidin. This is the first finding to prove that TA and NQ801 may protect tumor promoting potency from microbiological product.