2009 年 31 巻 2 号 p. 37-42
Animal studies have revealed that tea flavonoids, known as catechins, have the potential to prevent cancer. We investigated the genotoxicity of the 4 main green tea catechins, namely, (−)-epigallocatechin gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), and (−)-epicatechin (EC), using the comet assay in Chinese hamster CHL/IU cells. By measuring the percent of DNA in the comet tail, we concluded that EC, ECG, and EGCG did not induce biologically significant DNA damage. In contrast, EGC induced strong DNA damage at concentrations of 100 μM or higher. We further examined the genotoxic ability of EGC by the reverse mutation assay and the in vitro chromosome aberration test. The reverse mutation assay, revealed a maximum of 1.8-fold increase in the mean number of revertant colonies at 5000 μg/plate of EGC as compared to the number of colonies in the solvent control in Escherichia coli WP2uvrA/pKM101. EGC caused chromosome aberrations at low frequency in CHL/IU cells at a concentration of 200 μM. We concluded that EGC was weakly mutagenic in bacterial and mammalian cells.
