Purple rice bran extract attenuates the aflatoxin B1-induced initiation stage of hepatocarcinogenesis by alteration of xenobiotic metabolizing enzymes.

Pigmented rice bran has been suggested to be a valuable source of beneficial phytochemicals. We investigated genotoxic and anti-genotoxic effects of purple rice bran extract (PRBE) in rats using a liver micronucleus assay. Purple rice bran was extracted with methanol, obtaining large amounts of phenolic compounds, including anthocyanins and small amounts of gamma-oryzanol. The experimental protocols were divided into two sets. Male rats were divided into three groups. Group 1 was a negative control, while Groups 2 and 3 were fed with 100 and 500 mg/kg bw of PRBE, respectively, for 28 days. PRBE had no effect on micronucleus formation or xenobiotic metabolizing enzymes in rat liver. Experiments concerning the effect of PRBE on AFB1 showed that PRBE significantly lessened the amount of micronucleated hepatocytes in AFB1 treated rats. Furthermore, it modulated metabolic activation of AFB1 metabolism in the liver by suppressing activity and protein expression of CYP1A2, CYP3A and CYP 450 reductase, and enhancing phase II enzymes including GST and UGT. Overall, purple rice bran extract was not genotoxic in rats. It exhibited anti-genotoxicity by modulation some xenobiotic enzymes active in AFB1 metabolism.