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

Nattawan Suwannakul,Rawiwan Wongpoomchai,Charatda Punvittayagul,Kanokwan Jarukamjorn

doi:10.7314/apjcp.2015.16.8.3371

Nattawan Suwannakul, Rawiwan Wongpoomchai + Show 2 more

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https://doi.org/10.7314/apjcp.2015.16.8.3371

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Abstract

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.

Highlights

The rice bran or outer layer of the rice grain contains a number of micronutrients and valuable phytochemicals
The methanol extract of purple rice bran presented no mutagenicity in rat liver but it inhibited Aflatoxin B1 (AFB1) -induced mutagenicity in rats by decreasing the number of micronucleated hepatocytes
AFB1 is metabolized by CYP1A and 3A families

Summary

Introduction

The rice bran or outer layer of the rice grain contains a number of micronutrients and valuable phytochemicals. Several studies have shown that pigmented rice bran contains higher amounts of beneficial phytochemicals such as phenolic acids, flavonoids, anthocyanins, proanthocyanidins, tocopherols, tocotrienols, γ-oryzanol, phytic acid, free fatty acids and methyl ester derivatives (Leardkamolkarn et al, 2011; Jun et al, 2012; Goufo and Trindade, 2014) than colorless rice bran. Viral hepatitis B and C infections seem to be a pivotal cause of human liver cancer in Asian countries, this could be controlled by vaccination. AFB1 contamination in daily food is one cause of human liver cancer, it is difficult to completely avoid AFB1 exposure (Fan et al, 2013; Hamid et al, 2013)

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