Abstract:
The extracts from raw, cooked, and fermented of Hom Nil rice (Oryza sativa L.) and black glutinous rice (Oryza sativa L.) showed no mutagenicity on Salmonella typhimurium TA 98 and TA 100 in Ames test. After nitrite treatment in acid condition (pH3.0-3.5) the mutagenicity was detected. The mutagenic modification of rice extracts was evaluated using two models of mutagen; nitrite-treated chicken extract and nitritetreated 1-aminopyrene, and two models of antimutagenicity; antiformation and antimutagen. The results showed that the extract of cooked Hom Nil rice and all kinds of fermented rice could inhibit the formation of mutagen occurred during the reaction between nitrite and chicken extract and reaction between nitrite and 1-aminopynene respectively. The antiformation effect might be due to some components only in Hom Nil rice which increased after cooking and some components in fermented rice such as aglycone. These components might inhibit nitrosation and/or scavenge mutagen that occurred during nitrosation. However, the other rice extracts enhanced the mutagenicity of both mutagens. The study of antimutagenicity of rice extracts toward nitrite-treated chicken extracts and nitrite-treated 1-aminopyrene showed that all of rice extracts reduced the mutagenicity of both nitrite-treated mutagens. The protective effects of these rice extracts might be due to the presence of some components that might scavenge mutagens and/or inhibit bacterial enzyme. In addition, there were similar trends between the antimutagenicity of black glutinous rice extracts and the antioxidant activity and total phenolic contents assays; it was higher than that of Hom Nil rice extracts. The fermented rice extracts had the highest antioxidant activity and total phenolic contents. The results from this study suggested that black glutinous rice and Hom Nil rice were safe and were good sources of antioxidants which might be appreciated by health concerning consumers.
