Inhibition of 1,2-dimethylhydrazine-induced oxidative DNA damage in rat colon mucosa by black tea complex polyphenols

The effect of black tea polyphenols on 1,2-dimethylhydrazine (DMH)-induced oxidative DNA damage in rat colon mucosa has been investigated. Fischer 344 rats were treated orally with thearubigin (TR) or theafulvin (TFu) for 10 days (40 mg/kg), injected ip with DMH (20 mg/kg) or saline and sacrificed 2 4 hr after DMH administration. The levels of 8-hydroxy-2'-deoxyguanosine (8 -OHdG) were measured in colonic mucose DNA and expressed as a ratio relativ e to 2'-deoxyguanosine (2dG). Control rat mucosa had 8-OHdG values of 1.12 +/- 0.14/10(5) dG (mean +/- SEM, n = 11), whereas DMH-treated rats signific antly higher values (1.52 +/- 0.14/10(5) dG, n = 26, P < 0.05). Pretreatmen t of rats with TR had significantly inhibited DMH-induced oxidative DNA dam age 0.99 +/- 0.09/10(5) dG, n = 10, P < 0.05) and a similar, although less marked, effect was observed with TFu (1.15 +/- 0.19/10(5), n = 9, P = 0.06) . These findings confirm that DMH causes oxidative DNA damage in the colon mucosa of rats and demonstrate that this effect is prevented by the consump tion of complex polyphenols from black tea. (C) 2000 Published by Elsevier Science Ltd.