Excision-repair activity of green tea extracts in 4NQO-induced mutations of cultured Chinese hamster V79 cells

概要

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Hot-water extracts of green tea (Camellia sinensis) were examind for their antimutagenic actions on 6-thioguanin (6TG) -resistant mutations (HGPRT^-) induced by 4-nitroquinoline 1-oxide (4NQO) and ethyl methanesulfonate (EMS) in cultured Chinese hamster V79 cells. Green tea extracts (Polyphenons) reduced 4NQO-induced 6TG-resistant mutations to about one third or a half, when cells were post-treated with the green tea extracts after 4NQO treatment in the mutation expression time. On the other hand, the extracts were not effective in reducing EMS-induced mutations. Further studies were carried out to examine the effect of green tea extracts on 4NQO-induced DNA strand breaks in the excision repair process by using the fluorometric analysis of DNA unwinding (FADU) methods. The amount of DNA strand breaks in V79 cells, increased by treatment with 4NQO in incubation of cells in arabinofuranosyl cytosin and hydroxyurea (araC-HU) medium. The repair of DNA strand breaks was found when cells were incubated in araC-HU medium containing green tea extract after 4NQO exposure. These results indicate that the green tea extracts (possibly catechins) stimulated the repair process of nucleotide excision by removing the DNA adducts produced by 4NQO, and reduced the frequency of 6TG-resistant mutations in V79 cells.
日本環境変異原学会の論文
1999-07-12