Methanol extract from the stem of Cotinus coggygria Scop., and its major bioactive phytochemical constituent myricetin modulate pyrogallol-induced DNA damage and liver injury.

The present study was undertaken to investigate the hepatoprotective effect of the methanol extract of Cotinus coggygria Scop. in rats exposed to the hepatotoxic compound pyrogallol. Assessed with the alkaline version of the comet assay, 1000 and 2000mg/kg body weight (bw) of the extract showed a low level of genotoxicity, while 500mg/kg bw of the extract showed no genotoxic potential. Quantitative HPLC analysis of phenolic acids and flavonoids in the methanol extract of C. coggygria showed that myricetin was a major component. To test the hepatoprotective effect, a non-genotoxic dose of the C. coggygria extract and an equivalent amount of synthetic myricetin, as present in the extract, were applied either 2 or 12h prior to administration of 100mg/kg bw of pyrogallol. The extract and myricetin promoted restoration of hepatic function by significantly reducing pyrogallol-induced elevation in the serum enzymes AST, ALT, ALP and in total bilirubin. As measured by the decrease in total score and tail moment, the DNA damage in liver was also reduced by the extract and by myricetin. Our results suggest that pro-surviving Akt activity and STAT3 protein expression play important roles in decreasing DNA damage and in mediating hepatic protection by the extract. These results suggest that myricetin, as a major component in the extract, is responsible for the antigenotoxic and hepatoprotective properties of the methanol extract of C. coggygria against pyrogallol-induced toxicity.