Wereported previously that pyrolyzates of amino acids, peptides, proteins and proteinous foods were potently mutagenic toward Salmonella typhimurium TA98 and TA100.1)2) The pyrolyzates of sugars have been reported to show marked mutagenic activity toward TA100. 3) Recently, a new tester strain, TA97, for frameshift mutagens has been developed by Levin et al.4) In a preliminary experiment, we observed that TA97 is effective for mutagenicity detection of polycyclic aromatic hydrocarbons. Therefore, it was expected that the pyrolyzates of non-nitrogenous natural substances would show mutagenicity toward TA97.In this study, we found that pyrolyzates of natural substances such as organic acids, lipids and paraffin were more highly mutagenic toward TA97 than TA98 or TA100.The pyrolyzates were prepared from 5 sugars, 5 polyphenols, 4 organic acids, 4 lipids, paraffin and casein, which were of the purest grades available from commercial sources. About 3.0mg of each compound was put into a small quartz test tube (4mm O.D. and 0.5mm thick). The tube was evacuated to about 10"1 mmHg and then sealed with a flame at a length of about 40mm.Pyrolysis was performed in a Packard Tri-Carb Combustion Furnace, Model 325. Each sealed tube was placed in the middle of the pyrolysis column and heated at 500 to 800°C for 1 min. After removal and cooling, the tube was broken and its contents were dissolved in 800^1 of dimethyl sulfoxide (DMSO). Mutation assays with and without PCB-induced rat liver S9, prepared from male Sprague-Dawley rats, were performed using the methods described by Maron and Ames.5) The following bacterial strains were used;Salmonella typhimurium TA97, TA98 and TA100. A mixture of the tester strain, 0.1 ml ofa DMSO solution of the pyrolyzate and S9 mix or phosphate buffer were poured onto an agar overlayer. Assays employing liver homogenate were performed using 100/J of S9 per ml of S9 mix.After incubation for 48hr at 37°C, histidine-revertant colonies were counted. Each pyrolyzate was assayed in duplication.The effect of the pyrolysis temperature on the formation of the mutagens from malic acid is shown in Fig. 1. The temperature at which the maximalactivity was seen was 700°C. Therefore, organic acids, polyphenols, lipids, sugars, paraffin and casein were pyrolyzed at 700°C and the mutagenicactivities of the pyrolyzates were compared. The results are presented in Table I. Significant mutagenic activity was detected for the pyrolyzates of all test compounds toward TA97in the presence or absence of S9 mix, and these pyrolyzates, other than that of casein, exhibited higher mutagenic activity toward TA97than toward TA98 or TA100in the presence or absence of S9 mix. Among these pyrolyzates, higher mutagenic activity toward TA97 was detected for the pyrolyzates of organic acids, lipids and paraffin in the presence of S9 mix.In order to determine the mutagenicity distribution among the fractions of pyrolyzates of malic acid, the pyrolyzates were fractionated into neutral, acidic, phenolic and basic fractions, and the mu...
