Effects of hydrophilic compounds in purple rice husk on AFB1-induced mutagenesis

Abstract

Rice husk has been shown to possess cancer chemopreventive activity. This study focused on mutagenicity and antimutagenicity of the crude acidified methanolic extract of purple rice husk and its solvent- partitioned fractions using a Salmonella mutation assay and rat liver micronucleus test. The purple rice husk extracts were not mutagenic in S. typhimurium strain TA98, but were mutagenic in TA100 (crude extract and its hydrophilic fractions). There was no significant mutagenicity of purple rice husk extracts in rat liver. The rice husks possessed antimutagenicity against AFB1-induced mutagenesis in both bacterial and animal models. The dichloromethane-partitioned fraction (DPF) showed the highest antimutagenicity. Vanillic acid, a major phenolic compound found in DPF, exhibited antimutagenicity against AFB1 in both bacterial and rat models. The inhibitory mechanism was associated with the induction of detoxifying enzymes in AFB1 metabolism of rat liver. These findings suggested that vanillic acid may be a principal antimutagenic compound in purple rice husk.