Mutagenic activity of furfural in Salmonella typhimurium TA100.

The mutagenic activity of furfural was tested in Salmonella typhimurium strains TA98 and TA100. Furfural produced mutations in the TA100 strain, but not in the TA98 strain. A rat-liver microsomal fraction did not increase the mutagenic activity of furfural in either strain. Mutagenic activity of furfural in the TA100 strain was not increased by benzo[alpha]pyrene in the presence of metabolic activation.     

Mutagenic activity of furfural in Salmonella typhimurium TA100

The mutagenic activity of furfural was tested in Salmonella typhimurium strains TA98 and TA100. Furfural produced mutations in the TA100 strain, but not in the TA98 strain. A rat-liver microsomal fraction did not increase the mutagenic activity of furfural in either strain. Mutagenic activity of furfural in the TA100 strain was not increased by benzo[a]pyrene in the presence of metabolic activation.     

Mutagenic activities of selected nitrofluoranthene derivatives in Salmonella typhimurium strains TA98, TA98NR and TA98/1,8-DNP6

The mutagenic activities of novel nitrofluoranthene derivatives in Salmonella strains TA98, TA98NR and TA98/1,8-DNP6 (with and without S9 addition) are given. These derivatives were produced from the reactions of fluoranthene (FL) and its directly mutagenic 2- and 3-nitro derivatives with covalent dinitrogen pentoxide (N2O5) in CCl4 solution at ambient temperature. The influence of the addition of a nitro group on the observed activity of the resulting di- and tri-nitrofluoranthenes is discussed.     

Genetic toxicology evaluation of commercial beers. II. Mutagenic activity of commercial beer products in Salmonella typhimurium strains TA98, TA100 and TA102

5 concentrated extracts of commercial beers were prepared using XAD-2 resin. The residues were subjected to evaluation for mutagenic activity in Salmonella typhimurium strains TA98, TA100 and TA102. The tests were conducted using preincubation protocols including provisions for S9 metabolic activation. Although the extracts did produce moderate toxicity to the Salmonella organisms used in the assays, none of the residues were found to induce mutation up to their maximum testable concentrations.     

Mutagenicity of nitrofurans in Salmonella typhimurium TA98, TA98NR and TA98/1,8-DNP6

8 representative 2-substituted 5-nitrofurans were assayed for mutagenicity in Salmonella typhimurium strains TA98, TA98NR and TA98/1,8-DNP6. The tested compounds were: 5-nitro-2-furanacrylic N-(5-nitro-2-furfurylidene)hydrazide (1); furazolidone (2); 5-nitro-2-furanacrolein (3); 5-nitro-2-furaldehyde semicarbazone (4); 5-nitro-2-furaldehyde (5); nitrofurantoin (6); 5-nitro-2-furaldehyde diacetate (7); and 5-nitro-2-furoic acid (8). These compounds exhibited markedly different mutagenic activities in TA98, and these mutagenicities were similar both in the presence and the absence of rat-liver hepatic S9 activation enzymes. The mutagenic responses ranged from potent (90-300 revertants/nmole, compounds 1-3), to medium (about 10 revertants/nmole, compounds 4 and 6), to weak (0-4 revertants/nmole, compounds 5, 7 and 8). The mutagenicity of 3 was similar in all 3 tester strains, while compound 8 was essentially inactive. The mutagenicities of 1, 4, 5 and 7 were decreased 30-75% in TA98NR, while 2 and 6 showed an even greater depression of activity in this strain. Compound 6 with S9 was about equally mutagenic in TA98 and TA98/1,8-DNP6, while the activities of 6 without S9 and 2 and 7 both with and without S9 were 50-75% lower in TA98/1,8-DNP6. Compounds 1, 4 and 5 were only about 5-10% as mutagenic in TA98/1,8-DNP6 as in TA98. These results suggest that: (i) nitrofurans and their S9-mediated metabolites have similar mutagenic potencies; (ii) with the possible exception of No. 3, nitroreduction is the major route of mutagenic activation for these nitrofurans; and (iii) for compounds 2, 6 and 7, both the presumed N-hydroxy and N,O-ester derivatives of the corresponding aminofuran metabolites appear to lead to mutations.     

Mutagenic activity of acrinol in Salmonella typhimurium

Acrinol, which is used as a disinfectant and an abortifacient in several countries, was tested for mutagenicity by the Ames test system. After incubation with a rat-liver S9 microsomal preparation, acrinol showed potent mutagenicity for Salmonella typhimurium strains TA98 and TA100, although it had no direct mutagenicity for the microorganisms.     

Studies of the fatty acid composition and membrane microviscosity in Salmonella typhimurium TA98

When the mutagen tester bacterial strain Salmonella typhimurium TA 98 was grown at different temperatures, we found that the unsaturated fatty acid composition increased at the lower growth temperatures. Membrane microviscosity, as assessed with spin-probe fatty acids using electron spin resonance, decreased as the unsaturated fatty acid content increased. These findings are of importance in understanding our recent observation that the mutagenic response of these bacteria was increased when they were grown at 27 degrees C vs. 37 degrees C, and indicate that membrane properties may play an important role in the sequence of events leading to mutagenesis.     

Mutagenic activity of 6-aminoquinoxalines in Salmonella typhimurium

Mutagenicity of 6-aminoquinoxaline derivatives was tested with Salmonella typhimurium strains Ta98 and TA100 in the presence and absence of S9 mix from the viewpoint that the 6-aminoquinoxaline skeleton is a common unit of mutagenic imidazoquinoxalines. We tested nine compounds: 5-methyl-6-methylaminoquinoxaline (1), 3,5-dimethyl-6-methylaminoquinoxaline (2), 2,5-dimethyl-6-metnylaminoquinoxaline (3), 6-methylamino-2,3,5-trimethylquinoxaline (4), 2,3-diethyl-5-methyl-6-methylaminoquinoxaline (5), 5-methyl-6-methylamino 3-phenylquinoxaline (6), 6-amino-2,3,5-trimethylquinoxaline (7), 6-dimethylamino-2,3-5-trimethylaminoquinoxaline (8), 6-amino-2,3-dimethylquinoxaline (9). These compounds showed the mutagenic activity for both TA98 and TA100 in the presence of S9 mix, where they were more sensitive for TA100 strain. Methyl groups at the 2, 3 and/or 5 positions increased the potency of mutagenicity (1 < 2 < 3 ⪡ 4, 9 < 7). However, ethyl groups at the 2 and 3 positions lowered the mutagenicity of the methyl substitute but elevated it of the parental compound (1 < 5 < 4). A methyl group at the N⁶ position decreased the mutagenicity (7 > 4 > 8).     

Mutagenicity in Salmonella typhimurium TA98 and TA100 of nitroso and respective hydroxylamine compounds

Five aromatic nitroso compounds were prepared and their mutagenicity in Salmonella typhimurium strains TA98 and TA100 compared with that of the corresponding hydroxylamines and the previously studied nitroarenes. A remarkable correspondence of the dose-response curves was observed between the nitroso and the respective hydroxylamine compounds. This effect could be observed in TA98 and TA100. It was only marginally dependent on the metabolical activation by rat liver S9-mix. Even the presence of a bulky alkyl substituent either near to the functional group, or far away from it, previously shown to considerably influence the mutagenic properties of nitroarenes, does not remarkably affect the properties of the nitroso and hydroxylamine species. The similarity between the latter two is likely to be due to a fast reduction of the nitrosoarenes to the hydroxylamine species under the test conditions. It seems that enzymes are not responsible for that reduction step, because sterical crowding near the functional group does not influence that behaviour.The test results of the aromatic hydroxylamines bearing a bulky substituent show that there are at least two ways to influence the mutagenicity of an aromatic nitro compound by such a group. A substituent near the functional group (ortho-position) disturbs the enzymatic reduction of the nitro group, because 3-tert-butyl-4-hydroxylaminobiphenyl and its corresponding nitroso compound are highly mutagenic, whereas 3-tert-butyl-4-nitrobiphenyl was previously shown to be inactive even after addition of S9-mix. In contrast, 4'-tert-butyl-4-hydroxylaminobiphenyl with the tert-butyl group "far away" from the hydroxylamino functionality clearly shows decreased mutagenic activity suggesting a different influence of a substituent in that position. In addition, the substance shows only little cell toxicity even at higher concentrations. Both effects could be due to a reduced effective dose of the hydroxylamine in the cells compared to the non-alkylated compound, caused by a faster degradation of the hydroxylamine or a hindered interaction between that substance and the cells.     

Structure-mutagenicity relationships of 5-nitro-2-furylethylenes in Salmonella typhimurium TA98

Mutagenicity of three selected series of 2-furylethylene was determined by the Ames test. These included: nine alkylesters and eleven N-alkylamides of 5-nitro-2-furylacrylic acid (NFAA) and ten derivatives differing not only at exocyclic double bond, but also in the position 5 of the furan ring. Mutagenicity of the derivatives depends on the presence of the 5-nitro-furan centre in the molecule; side chains in the position 2 modify the degree of mutagenicity. Among the derivatives of NFAA tested as changing the substituents virtually does not affect chemical properties of the 5-nitrofuran ring. Mutagenicity of the n-alkyl congeners decreases linearly with increasing lipophilicity. Mutagenicity of the derivatives with branched alkyl substituents is lower than expected from the behaviour of the n-alkyl homologues.     

The mutagenic potencies of plant extracts containing quercetin in Salmonella typhimurium TA98 and TA100

Four commercial ethanolic plant extracts, Tinctura Alchemillae, Extractum Crataegi, Extractum Myrtilli and Tinctura Hyperici, were tested for their mutagenicity in Salmonella typhimurium TA98 and TA100 with and without S9 mix obtained from rats pretreated with phenobarbital. The extracts studied differed greatly in their mutagenic potencies but exhibited a very similar mutation pattern in which the strongest effect was always seen in tester strain TA98 with S9 mix. Simultaneously we investigated the extracts for the presence of quercetin and kaempferol. Only quercetin was detected in small amounts by thin-layer chromatography (TLC). The fractions containing quercetin were separated and collected using a Sephadex LH-20 column. Two different methods were employed to estimate the amount of quercetin in the extracts: a colorimetric assay developed by Christ and Müller, and a complexometric method by Belikov. The quercetin concentrations ranged between 2 mg (Tinctura Alchemilla) and 89 mg (Tinctura Hyperici) per 100 g of extract. We suggest that the mutagenicity of the 4 plant extracts is mainly due to the presence of quercetin for the following reasons: (1) all the plant extracts exhibit a mutation pattern which is very similar to that of quercetin, (2) the mutagenic potential of the extracts correlates well with their quercetin content, considering the fact that plant extracts are very complex mixtures often containing toxic or antimutagenic compounds.     

Mutagenic activity of Fusarium moniliforme isolates in the Salmonella typhimurium assay.

A total of 33 isolates of Fusarium moniliforme from several food or feed crops were grown on sterile cracked corn, and chloroform-isopropanol extracts were assayed for mutagenic activity in the Salmonella typhimurium-microsome system by using tester strain TA98 or TA100 or both. Extracts of 21 (64%) of the isolates assayed against TA100 were mutagenic. Activities of seven of these extracts were increased markedly with incorporation of the liver homogenate (S-9) into the assay. Seven (33%) of the isolates assayed against TA98 were weakly active, with the liver homogenate having little effect on reversion rates.     

Mutagenic activity of Fusarium moniliforme isolates in the Salmonella typhimurium assay.

A total of 33 isolates of Fusarium moniliforme from several food or feed crops were grown on sterile cracked corn, and chloroform-isopropanol extracts were assayed for mutagenic activity in the Salmonella typhimurium-microsome system by using tester strain TA98 or TA100 or both. Extracts of 21 (64%) of the isolates assayed against TA100 were mutagenic. Activities of seven of these extracts were increased markedly with incorporation of the liver homogenate (S-9) into the assay. Seven (33%) of the isolates assayed against TA98 were weakly active, with the liver homogenate having little effect on reversion rates.     

Measurement of drug-metabolizing systems in Salmonella typhimurium strains G46, TA1535, TA100, TA1538 and TA98

Salmonella typhimurium strains which are commonly used in the Ames test for screening potential carcinogens were examined for a number of drug-metabolizing systems. Neither cytochrome P-450 itself nor two activities catalyzed by the cytochrome P-450 system in mammalian cells, i.e., benzpyrene monooxygenase and ethoxycoumarin O-deethylation, could be detected. Nor do these bacterial strains demonstrate any ability to detoxify epoxides by hydrating them or to conjugate p-nitrophenol with glucuronic acid.On the other hand, S. typhimurium strains G46, TA1535, TA100, TA1538 and TA98 contain considerable amounts of acid-soluble thiols, approx. 5–10% of which is glutathione. These bacteria can also enzymatically conjugate glutathione with 1-chloro-2,4-dinitrobenzene (CDNB) and can reduce oxidized glutathione using NADPH as cofactor.Thus, enzymatic and non-enzymatic reaction of immediate carcinogens with thiol groups in S. typhimurium may have a significant effect on the outcome of the Ames test in certain cases.     

Mutagenic and inhibitory properties of some new purine analogs on Salmonella typhimurium TA1530

Mutagnic and growth-inhibitory effects of 2-amino-N⁶-hydroxyadenine, 2-amino-N⁶-methoxyadenine and 2-amino-N⁶-methyl-N⁶-hydroxyadenine were examined on S. typhimurium TA1530. All compounds showed strong mutagenic activity, and 2-amino-N⁶-hydroxyadenine induced mutations at a dose as low as 1 μg/ml. 2-Amino-N⁶-hydroxyadenine and, to a lesser extent, 2-amino-N⁶-methyl-N⁶-hydroxyadenine (but not 2-amino-N⁶-methoxyadenine) exerted inhibitory effects on bacterial growth. The specificity of mutagenic action of these base analogs, as well as the target for reversion of the his⁻ marker in TA1530, is discussed.