Mutagenicity of some commercially available nitro compounds for Salmonella typhimurium

Benzoyl chloride and 53 commercially available aromatic, heterocyclic and aliphatic nitro compounds were tested for mutagenicity in Salmonella typhimurium TA98 and TA100. 34 of 53 nitro compounds (64%) were mutagenic, 4 in TA100 only, 15 in TA98 only, and 15 in both strains. 13 of the heterocyclic derivatives of pyridine, indole, indazole, quinoline, and benzimidazole were mutagenic. 21 of 34 mutagenic nitro compounds were bactericidal. Nitromethane was the only aliphatic tested and was not mutagenic. Benzoyl chloride, a human carcinogen, was mutagenic for TA98.     

Mutagenicity to Salmonella typhimurium of some Aspergillus and Penicillium mycotoxins.

17 mycotoxins produced by various Aspergillus and Penicillium species were screened for their mutagenic activity to Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537, both with and without metabolic activation. Austdiol, austocystins A and D, kojic acid and viridicatumtoxin were found to be mutagenic after metabolic activation, while austdiol was also mutagenic per se. Aflatoxin B1, sterigmatocystin and versicolorin A, which were used as positive controls were also mutagenic. No mutagenic activity was evident in the case of citrinin, cyclopiazonic acid, fumitremorgen B, griseofulvin, luteoskyrin, O-methylsterigmatocystin, mycophenolic acid, ochratoxin A, patulin, penicillic acid, secalonic acid D and TR2-toxin. A good relationship was found between the mutagenic activity, or lack of it, of most of the mycotoxins with existing data on carcinogenicity. Inadequate information on the carcinogenicity of austdiol, austocystins A and D, kojic acid and viridicatumtoxin precluded correlations with mutagenicity to S. typhimurium. The relationship between chemical structure and mutagenicity of the mycotoxins is discussed.     

Mutagenicity of 22 N-nitrosamides and related compounds for Salmonella typhimurium TA1535.

Twenty-two N-nitrosamides and related compounds, including 14 nitrosoureas, 5 nitrosocarbamates, and one nitrosocyanamide, were tested at various concentrations for mutagenic activity towards Salmonella typhimurium TA1535 without the use of microsomes. The ether-water partition coefficient, solubility in water, and half-life in aqueous solution were also measured. Twenty compounds were mutagenic, with "standard mutagenic concentrations" (i.e. those producing 100 mutants/dish) of 0.0024--6500 micron. Standard mutagenic concentration was negatively correlated with the partition coefficient. Three compounds (ethyl 2-acetoxyethylnitrosocarbamate, nitrosocarbaryl, and methylnitrosobenzamide) were more active than the classic mutagen methylnitrosonitroguanidine. Nitrosocarbamates were at least 50 times more mutagenic than the corresponding nitrosoureas. Nitrosodihydrouracil and propylene-nitrosourea were more active than related compounds. Ethylnitrosocyanamide was 730 times more mutagenic than ethylnitrosourea. Fifteen of the test compounds (of which 14 were mutagenic) had previously been assayed in rats for carcinogenicity, all with positive results.     

Mutagenicity of streptozotocin and several other nitrosourea compounds in Salmonella typhimurium.

The following nitrosourea compounds were compared for their ability to induce mutation (to histidine independence) in the histidine-requiring auxotroph Salmonella typhimurium his G46: MNU, streptozotocin (SZ, streptozocin) and its analogs SZA1 and SZA2, and the antitumor drugs BCNU, CCNU and DCNU. At equitoxic doses SZ, SZA1, SZA2 and MNU were almost equally mutagenic causing 150, 42, 140 and 170 mutants/106 survivors at 20% lethal dose (ID20) ALTHOUGH, ON A WIEGHT BASIS, SZ was the most mutagenic of all the compounds tested. At ID20 BCNU, CCNU and DCNU gave about 0.5 mutants/106 survivors. Our results show that these nitrosoureas, in common with many other drugs (such as cyclophosphamide, daunomycin, etc.) used in cancer chemotherapy, are highly mutagenic. The implication of our results in the screening of drugs for their mutagenicity to man is discussed.     

Mutagenicity of nitrosodiethanolamine on Salmonella typhimurium.

Nitrosodiethanolamine was examined in the Ames assay for bacterial mutagens. In absence of S9 activation a mutagenic effect was found.     

Mutagenicity to Salmonella typhimurium of some Aspergillus and Penicillium mycotoxins

17 mycotoxins produced by various Aspergillus and Penicillium species were screened for their mutagenic activity to Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537, both with and without metabolic activation. Austdiol, austocystins A and D, kojic acid and viridicatumtoxin were found to be mutagenic after metabolic activation, while austdiol was also mutagenic per se. Aflatoxin B₁, sterigmatocystin and versicolorin A, which were used as positive controls were also mutagenic. No mutagenic activity was evident in the case of citrinin, cyclopiazonic acid, fumitremorgen B, griseofulvin, luteoskyrin, O-methylsterigmatocystin, mycophenolic acid, ochratoxin A, patulin, penicillic acid, secalonic acid D and TR₂-toxin.A good relationship was found between the mutagenic activity, or lack of it, of most of the mycotoxins with existing data on carcinogenicity. Inadequate information on the carcinogenicity of austdiol, austocystins A and D, kojic acid and viridicatumtoxin precluded correlations with mutagenicity to S. typhimurium. The relationship between chemical structure and mutagenicity of the mycotoxins is discussed.     

Mutagenicity of streptozotocin and several other nitrosourea compounds in Salmonella typhimurium

The following nitrosourea compounds were compared for their ability to induce mutation (to histidine independence) in the histidine-requiring auxotroph Salmonella typhimurium his G46: MNU, streptozotocin (SZ, streptozocin) and its analogs SZA₁ and SZA₂, and the antitumor drugs BCNU, CCNU and DCNU. At equitoxic doses SZ, SZA₁, SZA₂ and MNU were almost equally mutagenic causing 150, 42, 140 and 170 mutants/10⁶ survivors at 20% lethal dose (ID₂₀) although, on a weight basis, SZ was the most mutagenic of all the compounds tested. At ID₂₀ BCNU, CCNU and DCNU gave about 0.5 mutants/10⁶ survivors. Our results show that these nitrosoureas, in common with many other drugs (such as cyclophosphamide, daunomycin, etc.) used in cancer chemotherapy, are highly mutagenic. The implication of our results in the screening of drugs for their mutagenicity to man is discussed.     

Mutagenicity of aliphatic nitrosamines in Salmonella typhimurium.

25 aliphatic nitrosamines were examined in the Ames assay for bacterial mutagens, using rat liver "S-9" for activation. Of them, 8 carcinogens were mutagenic and 5 non-carcinogens were not mutagenic. However, 2 compounds not carcinogenic in rats were mutagenic and 9 carcinogens were not mutagenic, including 6 that are liver carcinogens in rats.     

Mutagenicity of N-nitrosopiperazine derivatives in Salmonella typhimurium.

Mutagenicity of several nitroso derivatives of piperazine was assayed using histidine auxotrophic strains of Salmonella typhimurium. Nitroso derivatives of piperazine required metabolic activation with preference to phenobarbital induced rat-liver microsomal enzymes. We observed a good correlation between a positive effect in the mutation assay and the carcinogenic potency of the compound. Even though our results are not in complete agreement with earlier published work using several microbial mutation assay systems, the differences we observed demonstrate the predictive value of an in vitro activation system using S. typhimurium to detect carcinogenic compounds as mutagens.     

Mutagenicity of diphenylhydantoin and some of its metabolites towards Salmonella typhimurium strains

The mutagenicities of 5,5-diphenylhydantoin (DPH) and its major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) were tested in vitro using different Salmonella strains (TA1535, TA100, TA1537, TA1538, TA98). Experiments were carried out at various concentrations in the absence and in the presence of an activating system consisting of hepatic S9 fraction from control rats and from rats pretreated with phenobarbital (PB), β-napthoflavone (BNF), 3-methylcholanthrene (3-MC) and Aroclor 1254 (PCB).DPH slightly increased the number of revertants per plate only after incubations with TA1538 in the presence of the S9 fraction from the liver of 3-MC- and PCB-pretreated animals. A similar but more significant frameshift mutation was observed for HPPH on both TA98 and TA1538 strains and in conditions of metabolic activation by the liver microsomal fractions of rats after pretreatment with BNF, 3-MC and especially PCB.Parallel experiments on the metabolism of DPH to HPPH and of HPPH to the catechol derivative in vitro support the hypothesis of an involvement of epoxide intermediates in the mutagenic activity of DPH.     

Mutagenicity of aliphatic nitrosamines in Salmonella typhimurium

25 aliphatic nitrosamines were examined in the Ames assay for bacterial mutagens, using rat liver “S-9” for activation. Of them, 8 carcinogens were mutagenic and 5 non-carcinogens were not mutagenic. However, 2 compounds not carcinogenic in rats were mutagenic and 9 carcinogens were not mutagenic, including 6 that are liver carcinogens in rats.     

Mutagenicity of methyl nitrite in Salmonella typhimurium

Methyl nitrite was tested for mutagenicity in Salmonella typhimurium TA1535. In the first set of experiments, plated bacteria were exposed to methyl nitrite in desiccators both in the absence and presence of a metabolizing system (S9 from Aroclor-pretreated Sprague-Dawley rats). Initial concentrations from 125 to 500 ppm were tested. In all experiments an increased initial concentration gave an increased mutagenic response. The mutagenic effect in the presence of S9 was similar to that in the absence of S9. Owing to difficulties in dose determinations in this type of experiment it could not be decided, unequivocally, whether the mutagenic effect was caused by methyl nitrite or its hydrolysis products. Experiments were therefore carried out in suspension, and the concentrations of methyl nitrite and inorganic nitrite were determined. Treatments with inorganic nitrite were also carried out under similar conditions. From the results of these experiments we concluded that methyl nitrite is mutagenic. Possible mechanisms of action of methyl nitrite are discussed, and it is suggested that mutagenicity may be a general property of alkyl nitrites.     

Mutagenicity of substituted phenanthrenes in Salmonella typhimurium

An extensive series of alkylated phenanthrenes was assayed for mutagenic activity in Salmonella typhimurium TA98 and TA100. Among the alkylated phenanthrenes assayed, 1-methylphenanthrene, 9-methylphenanthrene, 1,4-dimethylphenanthrene and 4,10-dimethylphenanthrene were active as mutagens. These studies suggest that the structural requirements favoring mutagenic activity among alkylated phenanthrenes are inhibition of 9,10-dihydrodiol formation and the presence of an unsubstituted angular ring adjacent to a free peri position. The mutagenic activities of 9-fluoro-, 9-chloro-, and 9-bromo-phenanthrene were also evaluated. The positive mutagenic response of these halogenated phenanthrenes further supports the observation that inhibition of 9,10-dihydrodiol formation among substituted phenanthrenes favors mutagenic activity.     

Mutagenicity of oxaspiro compounds with Salmonella

The spiro attachment of an epoxide group to a tetrahydropyran ring in the trichothecene mycotoxins has prompted this study of the mutagenicity and alkylation rates of the trichothecene, anguidine, and 5 related model oxaspiro compounds. While the model compounds were weak alkylating agents of 4-(4-nitrobenzyl)pyridine as a test nucleophile, anguidine lacks such activity. Also, while mutagenicity was not established for anguidine in Salmonella TA100, 3 of the oxaspiro compounds were weakly mutagenic and 2 compounds were toxic to the bacteria. The toxicity and mutagenicity of the model compounds are more related to their polarity than to their alkylation rates.