Inhibitory effects of Cassia tora L. on benzo [a]pyrene-mediated DNA damage toward HepG2 cells

The effects of water extracts from Cassia tora L. (WECT) treated with diffe rent degrees of roasting on benzo[a]pyrene (B[a]P)-induced DNA damage in hu man hepatoma cell line HepG2 were investigated via the comet assay without exogenous activation mixtures, such as S9 mix. WECT alone, at concentration s of 0.1-2 mg/mL, showed neither cytotoxic nor genotoxic effect toward HepG 2 cells. B[a]P-induced DNA damage in HepG2 cells could be reduced by WECT i n a dose-dependent manner (P < 0.05). At a concentration of 1 mg/mL, the in hibitory effects of WECT on DNA damage were in the order unroasted (72%) > roasted at 150 degreesC (60%) > roasted at 250 degreesC (23%). Ethoxyresoru fin-O-dealkylase activity of HepG2 cells was effectively inhibited by WECT, and a similar trend of inhibition was observed in the order unroasted (64% ) > roasted at 150 degreesC (42%) > roasted at 250 degreesC (18%). The acti vity of NADPH cytochrome P-450 reductase was also decreased by unroasted an d 150 degreesC-roasted samples (50% and 38%, respectively). Furthermore, gl utathione S-transferase activity was increased by treatment with unroasted (1.26-fold) and 150 degreesC-roasted (1.35-fold) samples at 1 mg/mL. In add ition, the contents of anthraquinones (AQs) in WECT, including chrysophanol , emodin, and rhein, were decreased with increasing roasting temperature. E ach of these AQs also demonstrated significant antigenotoxic activity in th e comet assay. The inhibitory effects of chrysophanol, emodin, and rhein on B[a]P-mediated DNA damage in HepG2 cells were 78, 86, and 71%, respectivel y, at 100 muM. These findings suggested that the decreased antigenotoxicity of the roasted samples might be due to a reduction in their AQs content.