Suppression of aflatoxin mutagenicity by spermine

362 be mutagenic to S. typhimurium TA100 without $9 mix. Cytosol fraction of the livers of rats treated or not treated with PCB suppressed the mutagenicity of coffee. This suppressing factor was partially purified from rat liver cytosol. It was identified to be catalase by a specific antibody against rat liver catalase. Catalase suppressed more than 80% of the mutagenicity of coffee. In addition to catalase, horseradish peroxidase suppressed coffee mutagenicity. Glutathione peroxidase with reduced glutathione also suppressed the coffee mutagenicity. Freshly prepared instant coffee solution at the concentration of 15 m g / m l contained 130 /~M hydrogen peroxide. Production of hydrogen peroxide should be related to heated polyphenolic c o m p o u n d s in coffee. H y d r o g e n peroxide accounted only for less than 5% of the total mutagenicity of coffee. Mutagenicity and hydrogen peroxide disappeared by the addition of catalase, but reappeared after inactivation of catalase by the addition of a specific antibody against catalase. Therefore, major mutagens in coffee should be unstable but should be continuously produced in coffee solution in the presence of hydrogen peroxide.

4 Fukuhara, Y., D. Yoshida and S. Mizusaki, Central Research Institute, The Japan Tobacco and Salt Public Corporation, Yokohama (Japan)

Inhibition of mutagenicity of peroxide by polyphenols Effects of polyphenols on the mutation frequency of tert-butyl hydroperoxide (tBH) were determined using a new tester strain S. typhimurium TA102. Catechol, tannic acid, pyrogallol, gallic acid and n-propyl gallate markedly inhibited mutagenicity of tBH without decreased survival. Weak inhibition was also obtained by protocatechuic acid, quercetin, chlorogenic acid, catechin and rutin. When tannic acid was added to the bacteria treated previously with tBH, the number of His ÷ colonies was not reduced. The mutagenicity of mitomycin C was not affected by these

polyphenols. The possible mechanism of these inhibitions was tested. No chemical reaction of tBH with tannic acid was detected. No degradation of tBH by bacterial enzyme such as peroxidase occurred in the presence of polyphenols. Studies are in progress to examine other possibilities.

5 Furukawa, H., K. Kawai, N. Okado, M. Haruna and K. Ito 1 Laboratory of Environmental Science, and 1 Laboratory of Natural Products Chemistry, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya (Japan)

Suppression of aflatoxin mutagenicity by spermine The mutagenicity of aflatoxin G 1 on Salmonella typhimurium TA100 and TA98 was suppressed by addition of spermine. Studies with N M R and UV spectra showed hydrogen-bond formation between aflatoxin G 1 and spermine, suggesting a possible mechanism for this suppression.

6 Fuse, M., and H. Nishioka, Biochemistry Laboratory, Doshisha University, Kyoto (Japan)

Effect of pH on mutagenicity of quercetin The effect of pH on the mutagenicity of a flavonoid compound, quercetin, in Salmonella typhimurium strains TA98 and TA100 was investigated. Experimental materials and procedures have been described in our paper that appeared in The Science and Engineering Review of Doshisha Univ. (24 (1983) 70-74). When quercetin was pretreated at pH 1.0, the numbers of revertant colonies observed in the assay on both strains increased significantly compared with those in a control where quercetin was pretreated at pH 7.4. When the treatment was done at pH 9.4, the mutagenicity was no longer detectable. A similar effect was observed when quercetin was pre-incubated with the tester strains in the medium at different pHs such as 6.4, 7.4 and 8.4. No signifi-