Antimutagenic activity of Hom Nil rice and Black Glutinous rice in somatic mutation and recombination test

Abstract

Raw, cooked and fermented Hom Nil rice and black glutinous rice were assessed for their mutagenicity and antimutagenicity against both urethane and in vivo formed nitrosomethylurea using somatic mutation and recombination test in Drosophila melanogaster. Three-day old, trans-heterozygous (mwh flr+/mwh TM3) larvae obtained by mating virgin ORR flare hair females and mwh/mwh males were transferred to experimental media that contained each sample substituted for corn flour. The round wings of the surviving adult flies were analyzed for the occurrence of mutant spots. The results indicated that all samples did not significantly induce the frequencies of mutant spots at any testing amounts. The study of antimutagenicity of each sample against urethane (20 mM) showed that all samples reduced the mutagenicity of urethane, and the fermented Hom Nil rice possessed higher antimutagenicity than the other did. The antimutagenicity of each sample might possibly be due to their antioxidants or phenolic compounds which might scavenge the mutagen and/or free radicals occuring during mutagenesis. Furthermore, the study exhibited that Hom Nil and black glutinous rice showed antimutagenic effect against in vivo formed nitrosomethylurea, and the fermented black glutinous rice possessed the highest antimutagenicity. It is proposed that some components of rice might reduce the amount of N-nitrosomethylurea formed during the reaction between the methylurea and sodium nitrite. Therefore, this study suggests that Hom Nil rice and black glutinous rice are safe for health concerning consumers. Further study should be conducted to investigate the active compound(s) and mechanism of antimutagenic activity of pigmented rice.