The purpose of this study was to investigate the mutagenic and antimutagenic interactions between several fractions of saliva and the habitual oral bacteria. Antimutagenicity was examined against the known mutagenic substances, 4-nitroquinoline-1-oxide (4NQO), AF-2 and benzo[a]pyrene (B[a]P)), using Salmonella typhimurium strains TA98 and TA100 in Ames test and Rec ם and Rec מ strains of Bacillus subtilis of Rec-assay. Four fractions from human saliva, whole saliva, supernatant saliva (Sup), precipitation in saliva (PPT) and heated saliva (Heat), were examined against 4NQO, AF-2 and B[a]P-induced mutagenicity. The whole saliva exhibited the strongest antimutagenic activity amongst all fractions applied against 4NQO and AF-2 in Ames test with more than an 80% inhibition rate. However, the whole saliva had an activity of only 50% inhibition against BP. The potency of the antimutagenicity was in the following order: whole salivaϾSupϾPPTϾHeat, in Ames test. Rec-assay also exhibited a pattern of antimutagenicity similar to that of Ames test. The cultured supernatants of the oral anaerobic bacteria exhibited a weak mutagenic potency. The cell wall skeletons of the oral anaerobic bacteria exhibited stronger antimutagenic activity against each mutagen than that of the oral aerobic bacteria. cause of human cancer is from environmental factors and, although it may conflict with current lifestyles, avoiding these factors may be the best method for cancer prevention 3,4). Another means for preventing mutagenesis would be the consumption of antimutagen 5,6). Therefore, significant attention has been focused on the antimutagenic factors that reduce the spontaneous and induced mutagenesis. Recent studies suggest that the polyphenols in fruits and vegetables are active antioxidants with antimutagenic and anticarcinogenic properties 5-8). Hour et al. 9) reported that various tea extracts and their components exhibited antimutagenic activities against the mutagenicity induced 2-acetylamino-fluorene and N-methyl-N'-nitro-N-nitrosoguanidine in Ames test. We previously reported that the bamboo extract, lignin 10) and royal jelly 11,12) exhibited inhibitory
Methyl radicals generated by di-t-butylperoxide pyrolys~s interact at comparable rates with cisbutene-2 in the gas phase by both addition and hydrogen atom abstraction. The determination of the rate of these reactions was simplified by the addition of a large concentration of acetaldehyde to the system. The additive, a source of low activation energy abstractable hydrogen atoms, was effective in suppressing polymerization reactions, and in addition, maintained a high steady state methyl radical concentration as a result of the carbonyl radical decomposition. The rate constants, k5 and k6 for the reactions [5] and [6], were determined to be 4.5 x 101° exp (-7000JRT)and 1.8 x 101° exp (-7300/RT) cm3 mole-' s-', respectively, over thc tcmperature range 126-163 ' C . The butenyl radical formed in reaction [6] isomerizes much faster than its interaction with other species in the system, and the distribution of the various conformations is similar to the equilibrium distribution of the butenes at a similar temperature.
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