• cytochrome P4501A1;
  • enzyme induction;
  • enzyme inhibition;
  • flavonoids;
  • pre-carcinogens activation

Flavonoids, plant secondary metabolites present in fruits and vegetables, show antioxidant and anti-tumorigenic effects in vitro, but their poor absorption from gastrointestinal tract limits their systemic efficacy in humans. On the other hand, flavonoids could protect intestinal cells against carcinogens by their potential to inhibit the enzymes metabolizing pre-carcinogenic compounds (e.g. CYP1A) to reactive ones. This work was designed to test the effect of quercetin (the most abundant flavonoid) and rutin (the most abundant glycosidic form) on the activity, expression and inducibility of CYP1A in intestinal HCT–8 cells. CYP1A enzymatic activity was measured by ethoxyresorufin-O-deethylase (EROD) activity, CYP1A protein expression was detected by western blotting. The effect of flavonoids on viability of cells was examined by neutral red uptake test. No cytotoxic effect of flavonoids up to 50 μM concentration was observed. Quercetin significantly inhibited EROD activity in the cells, where CYP1A had been preinduced by β-naphthoflavone and methylcholanthrene, and it also significantly reduced the CYP1A induction mediated by these model inducers. The effect of rutin was substantially weaker and mostly insignificant in all conducted experiments. The results suggest that quercetin may have a potential to limit the CYP1A-mediated activation of pre-carcinogens in intestinal cells. Copyright © 2013 John Wiley & Sons, Ltd.