Structure-dependent variation in the mutagenic, prophage-inducing and antibacterial activities of 5-nitro-2-furamide derivatives

A comparative survey of the mutagenic, prophage-inducing and antibacterial activities of 3 structure-related series of 5-nitro-furan derivatives including 5-nitro-2-furohydrazide imide, 5-nitro-2-furamide oxime and 5-nitro-2-furohydrazide has been undertaken. Among the compounds assayed, the 5-nitro-2-furohydrazide imide series was found to be most active with regard to mutagenic and antibacterial activities against Salmonella typhimurium TA100 and prophage-inducing activity in Escherichia coli GY5027. A clear correlation was observed between the chemical structure and the mutagenic and prophage-inducing activities which were approximately correlated to the antibacterial activity.     

The mutagenic action of nitroimidazoles. IV. A comparison of the mutagenic action of several nitroimidazoles and some imidazoles.

The mutagenic action of 51 imidazoles was investigated. The fluctuation test of Luria and Delbrück was used, with Klebsiella pneumoniae as test organism. 8 compounds, including 5 with a weak mutagenic action in the fluctuation test, were also investigated by the Ames test in which Salmonella typhimurium TA100 was used. Of the 51 imidazoles examined, 33 were nitroimidazoles. 31 of the latter appeared to be mutagenic, whereas out of the 18 other imidazoles without a nitro group only 2 were mutagenic. Several of the substances tested for mutagenicity showed an antimicrobial activity. No direct relationship between antimicrobial action, growth inhibition and mutagenicity was established. With methyl-nitroimidazoles a relationship was found between the chemical structure and mutagenic action. However, when the nitroimidazoles had a more complex chemical structure, a relationship between this structure and mutagenicity could not be established.     

Study on the mutagenicity of nifurtimox and eight derivatives with the L-arabinose resistance test of Salmonella typhimurium

The mutagenicity of nifurtimox (nfx) and 8 nfx analogues has been investigated with the L-arabinose forward-mutation assay of Salmonella typhimurium. The nfx analogues tested were obtained by replacing the 3-methyl-4-yl-tetrahydro-1,4-thiazine-1,1-dioxide group of the parent compound with the following other groups: indazol-1-yl (1); pyrazol-1-yl (2); benzimidazol-1-yl (3); 1,2,4-triazol-4-yl (4); 1-methyl-3-methylthio-1,2,4-triazol-4-yl-5-thione (5); 3,5-bis(methylthio)-1,2,4-triazol-4-yl (6); 1-adamantyl (7); 4,6-diphenylpyridin-1-yl-2-one (8). The mutagenic activity of each chemical was determined by the standard plate-incorporation test, in the presence or absence of the S9 activation mixture. The 9 compounds were mutagenic and exhibited linear dose-mutagenic response relationships. They were direct-acting mutagens and showed a nearly 1000-fold range in mutagenic potency from chemical 1 to nfx. In most cases, the addition of S9 mixture to the test plates decreased the mutagenicity of compounds. This effect was particularly noticeable in the case of chemicals 1-3, 5 and 7 where a more than 70% decrease in mutagenic activity was observed in the presence of the S9 mixture. The mutagenic potency of compounds in the Ara test showed a negative linear correlation with previously reported antitrypanosomal activity. Thus, chemicals 6 and 8 with in vitro activities against Trypanosoma cruzi clearly superior to that of nfx showed 2 of the lowest mutagenic potencies in the Ara test and these were only somewhat higher than the mutagenicity of the reference drug.     

Structural determination of a directly mutagenic amino-nitrobiphenyl as the S9 metabolite of 2,4,2',4'-tetranitrobiphenyl in Salmonella typhimurium TA98.

In order to elucidate the mechanisms of mutagenic activation of nitrobiphenyls by mammalian activation systems, 2,4,2',4'-tetranitrobiphenyl was incubated with S9 and its mutagenic metabolites were separated by SiO2 and Al2O3 column chromatography. The most mutagenic diamino-dinitrobiphenyl was isolated from the reaction mixture of 2,4,2',4'-tetranitrobiphenyl with S9 mix at 37 degrees C for 48 h, and its mutability was 4646 revertants/50 ng in Salmonella typhimurium TA98 without S9 mix. The deamination product of this most mutagenic metabolite was identical to 2,4'-dinitrobiphenyl by gas chromatography-mass spectrometry. Therefore, the structure of the metabolite was determined as 2,4'-diamino-2',4-dinitrobiphenyl by its chemical and physico-chemical properties.     

Effect of dioxidine, antineoplastic agents and other mutagens on the precise excision of Tn1 and Tn10 transposons in E. coli K12

Induction of precise excision of transposons Tn1 and Tn10 from the genes met::Tn1 and cys::Tn10 by chemical agents, having mutagenic and DNA damaging activities, has been studied. The drugs dioxydin, NMU, photrin, phopurine, thiophosphamid, rongeron as well as sodium azide, 2-NP, DDDTDP are shown to differ in their ability to stimulate the precise excision of transposons of different classes and in the efficiency of stimulated process. Results of the present paper are in proof of the possible using of experimental model, based on registering the precise excision of transposons, for screening the mutagenic and cancerogenic activities of chemical agents from the environment.     

Mutagenic potency of food-derived heterocyclic amines

The understanding of mutagenic potency has been primarily approached using "quantitative structure-activity relationships" (QSAR). Often this method allows the prediction of mutagenic potency of the compound based on its structure. But it does not give the underlying reason why the mutagenic activities differ. We have taken a set of heterocyclic amine structures and used molecular dynamic calculations to dock these molecules into the active site of a computational model of the cytochrome P4501A2 enzyme. The calculated binding strength using Boltzman distribution constants was then compared to the QSAR value (HF/6-31G* optimized structures) and the Ames/Salmonella mutagenic potency. Further understanding will only come from knowing the complete set of mutagenic determinants. These include the nitrenium ion half-life, DNA adduct half-life, efficiency of repair of the adduct, and ultimately fixation of the mutation through cellular processes. For two isomers, PhIP and 3-Me-PhIP, we showed that for the 100-fold difference in the mutagenic potency a 5-fold difference can be accounted for by differences in the P450 oxidation. The other factor of 20 is not clearly understood but is downstream from the oxidation step. The application of QSAR (chemical characteristics) to biological principles related to mutagenesis is explored in this report.     

Genotoxic and mutagenic activity of environmental air samples from different rural, urban and industrial sites in Flanders, Belgium

The present study reports mutagenic and genotoxic activities associated with ambient air collected at 15 sites characteristic for urban, industrial or rural conditions in Flanders. Airborne particulates (PM10) and semi-volatile compounds were collected on quartz filters (QF) and polyurethane foam (PUF) cartridges using a high-volume sampling device. The mutagenic and genotoxic potency of the organic extracts--Soxhlet extraction with acetone--was determined by use of the Salmonella mutagenicity standard plate-incorporation assay and the Vitotox assay, respectively. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC). Ambient air samples contained significant PAH levels and mutagenic activities at all 15 sites: direct mutagenicity of up to 47 revertants per cubic meter was found in the QF extracts and more limited activity of up to 11 rev m(-3) in the PUF extracts. Metabolic activation of PUF extracts resulted in an important increase in mutagenic activity, up to 30 rev m(-3), but no such increase was observed for QF extracts. The highest values were observed outside large cities at industrial sites and at a rural site contaminated by pollution from a chemical plant at a distance of 4 km. Also at the background location near the North Sea a significant mutagenic activity was measured in the QF extracts (+S9: 9 rev m(-3); -S9: 7 rev m(-3)). Apparently, there is in Flanders a significant background exposure level to airborne mutagenicity, even in areas with limited or no nearby pollution sources. Based on the concentrations of 10 mutagenic PAHs and supposing additivity of their specific mutagenicities, only a few percent (mean 3%) of the observed indirect mutagenic activity could be explained. This implies that most mutagenic activity originated from other substances that were not identified or measured in our chemical analysis. This underscores the importance of bio-monitoring measurements.     

Structure-activity relationships of a series of antitumoral 5,8-quinazolinediones in mutagenicity studies.

Four antitumoral 5,8-quinazolinediones were examined for their ability to induce mutation in Salmonella typhimurium. Each compound was tested at several concentrations in 4 strains. Relationships were established between the structure of the quinones and their mutagenic activities. The mutagenicity was influenced by (i) the nature of the substituent(s) of the quinonic moiety: the methoxyquinone had no mutagenic properties and the aziridinylquinones were mutagenic in the 4 strains with or without activation by S9 mix; (ii) the presence or the absence of a diaminopolymethylenic chain in the 4 position; (iii) the monomeric or the dimeric structure of the tested compound. Interestingly, the data indicated that the aziridinylquinazolinedione bearing the dimethylaminopropylamino chain in the 4 position was less mutagenic and had greater antitumor activity than the dimeric quinone.     

Mutagenic activity and structure-activity relationships of short-chain dialkyl N-nitrosamines in a hamster hepatocyte V79 cell-mediated system

A series of 19 short chain dialkyl N-nitrosamines was studied for mutagenic activity in an uninduced hamster hepatocyte V79 cell-mediated mutagenesis system. Ouabain was used as the selective agent to quantitatively analyze for chemically induced mutants. None of the nitrosamines was mutagenic in the absence of hamster hepatocyte activation. The relative mutagenic activities of the nitrosamines at an equimolar dose are presented. The results of the study indicated that: (a) increasing alkyl chain length decreased mutagenic activity; (b) oxidation of the carbon position to a carbonyl group increased the mutagenic activity of symmetrical and asymmetrical nitrosamines, whereas oxidation to a hydroxyl group only increased the mutagenic activity of the asymmetrical nitrosamines tested and (c) the carbon position at which oxidation occurred was important in determining mutagenic activity. The relationships between structure, metabolic activation, and mechanisms of mutagenic activity are discussed.     

Ames test: mutagenic activity of airborne particles collected on airconditioner filters during the fire at a Sandoz storehouse in Schweizerhalle on November 1, 1986

The mutagenic activity of methanol extracts from airconditioner filters was tested using the standard plate-incorporation procedure for the Ames test and the strains Salmonella typhimurium TA97, TA98 and TA100 as test organisms. In a first set of experiments filters from 4 buildings were investigated. For each building the mutagenic activity of a filter which was in use during the fire (fire-exposed) was compared with the mutagenic activity of a filter which was exposed for a similar time span to normal urban air (non-exposed). While for 1 pair of filters the non-exposed extract was more mutagenic than the fire-exposed material, the opposite was found for 2 other filter pairs, and in 1 case there was hardly any difference in the mutagenic activities of the fire-exposed and the non-exposed filter extracts. Overall differences by factors up to 100 were observed in the mutants/m3 air values of the most and the least mutagenic filter extracts. The second group of experiments was performed to investigate the variations in mutagenic activity of filter extracts occurring due to changes in the weather conditions. Airborne particles were collected for 3 consecutive periods of 10-11 days at the 2 buildings where the extracts of the fire-exposed filters had been found to be more mutagenic than the corresponding control materials. The differences between the strongest and the weakest mutagenic filter extracts of these series were similar to the differences observed previously between the fire-exposed filters and the non-exposed filter materials. The highest mutagenic activities found in the second group of experiments was similar, at both sites, to the mutagenic activities measured in the fire-exposed extracts from these 2 buildings. Since the differences in the mutagenic activities of filters exposed to urban air during the different meteorological conditions were similar to the differences observed between fire-exposed and non-exposed materials, it is not possible to state whether the fire led to the distribution of mutagenic chemicals, although it is theoretically possible. However, based on the observation that the maximal mutagenic activities of the fire-exposed and the non-exposed extracts were similar, the present study allows the conclusion that the mutagenic burden for the population of the area of Basel was not significantly increased by the fire in Schweizerhalle on November 1, 1986.     

Relative efficiencies of a series of square-planar plantinum(II) compounds on Salmonella mutagenesis.

Twelve Pt(II) compounds have been tested for mutagenicity on Salmonella typhimurium (strain TA 100). Very high mutagenic activities were found for the cis derivatives. A correlation is suggested between these results and a formerly described model of chemical reactivity towards DNA, according to which cis derivatives from intra-strand chelates with guanine. A smaller activity was found with monodentate complexes with DNA.     

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 and chemical reactivity of epoxidic intermediates of the isoprene metabolism and other structurally related compounds

The mutagenic activities of the epoxidic intermediates of the isoprene biotransformation were investigated using Salmonella typhimurium and compared with those of other structurally related epoxides. The compound 2-methyl-1,2,3,4-diepoxybutane, chemically analogous to the well known carcinogenic 1,2,3,4-diepoxybutane, was found to be as mutagenic as the latter. Moreover, the mutagenic activities of oxiranes were correlated to their alkylating powers towards nicotinamide and to their half-lives for spontaneous hydrolysis. The relationship between alkylating power and mutagenicity was found to hold for the stable epoxides that react mainly by an SN2 substitution mechanism.     

Mutagenic activity of the leachate of municipal solid waste landfill.

Organic concentrates were recovered using XAD-2/8 resin adsorption from the leachates of municipal solid waste landfills and their mutagenic activities were tested for 8 months using the Ames Salmonella/microsome assay. Highly polluted leachates (COD and BOD > or = 40 mg/l) generally had equal or higher mutagenic activities than lightly polluted leachates (COD and BOD < 40 mg/l). But there was no clear difference in mutagenicity per amount of concentrate between the two leachates. These results suggest that the mutagenic activity of landfill leachate is decided to some degree by the organic concentration in the leachate. The mutagenic activities detected even in lightly polluted leachates were not so low as those of various kind of surface waters ever reported. It is suggested that it is important to investigate the mutagenic activity of the leachate for evaluation of the impact of landfill leachate on the environment.     

Mutagenicity studies on complex environmental mixtures: selection of solvent system for extraction.

The mutagenic activities in the Salmonella/microsome assay of dichloromethane (DCM) and acetone extracts of complex environmental mixtures were compared. The particulate samples used in the IPCS collaborative study were Soxhlet-extracted twice with DCM followed by a third extraction with acetone. Compared with the mutagenic activity of the first extract, the third (acetone) extract of the urban particulate matter showed a relatively high mutagenic activity. In contrast to this the third extract of the diesel particulate matter contributed very little additional mutagenic activity. Furthermore, 10 filter samples of air particulates from a suburban airport area were collected for comparison of the extraction efficiency of DCM and acetone. Each sample was divided into two samples of identical size followed by extraction with acetone and DCM, respectively. No clear difference in the mutagenic activity of these extracts was observed in strains TA98 and TA98NR. It is concluded that for ambient air particulates (but not emission samples) acetone may extract some mutagenic compounds which are not extracted by DCM. The amount of these additional extractable compounds seems to depend on the composition of the sample. As DCM extracts are better suited for further fractionation and chemical analysis DCM is considered to be the best choice for a general solvent system for extraction of complex environmental mixtures.     

The use of the Salmonella/microsomal assay to determine mutagenicity in paired chemical mixtures.

The mutagenicities of two sets of chemicals acting singly and in pairwise combinations were determined by use of the Salmonella/microsomal assay. The first set consisted of the promutagens of benzo(a)pyrene and benzo(rst)pentaphene. The second set contained the direct-acting mutagens methyl-nitro-nitroso-guanidine and ethyl methane sulfonate. In the tests with the promutagens, the quantities of S-9 mix were varied over the range of 0.05 ml to 1.0 ml with increasing quantities of each chemical. The mutagenic responses or production of revertant colonies of the promutagens, acting singly and in pairwise combinations failed to show an additive effect. Excess quantities of S-9 mix appeared to inhibit partially or totally the mutagenic activity of each chemical, although for each particular dose there was an optimal quantity of S-9 mix to induce maximum activity. However, the direct-acting mutagens produced, individually, almost linear dose responses with increasing concentrations. In pairwise combinations, these chemicals also showed linear responses that closely approximated the theoretical additivity indicating that the mutagenicity of the mixtures was the sum of the activities of each component.     

Genotoxic and mutagenic activity of environmental air samples from different rural, urban and industrial sites in Flanders, Belgium

The present study reports mutagenic and genotoxic activities associated with ambient air collected at 15 sites characteristic for urban, industrial or rural conditions in Flanders. Airborne particulates (PM10) and semi-volatile compounds were collected on quartz filters (QF) and polyurethane foam (PUF) cartridges using a high-volume sampling device. The mutagenic and genotoxic potency of the organic extracts – Soxhlet extraction with acetone – was determined by use of the Salmonella mutagenicity standard plate-incorporation assay and the Vitotox^® assay, respectively. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC).Ambient air samples contained significant PAH levels and mutagenic activities at all 15 sites: direct mutagenicity of up to 47 revertants per cubic meter was found in the QF extracts and more limited activity of up to 11 rev m⁻³ in the PUF extracts. Metabolic activation of PUF extracts resulted in an important increase in mutagenic activity, up to 30 rev m⁻³, but no such increase was observed for QF extracts. The highest values were observed outside large cities at industrial sites and at a rural site contaminated by pollution from a chemical plant at a distance of 4 km. Also at the background location near the North Sea a significant mutagenic activity was measured in the QF extracts (+S9: 9 rev m⁻³; −S9: 7 rev m⁻³). Apparently, there is in Flanders a significant background exposure level to airborne mutagenicity, even in areas with limited or no nearby pollution sources. Based on the concentrations of 10 mutagenic PAHs and supposing additivity of their specific mutagenicities, only a few percent (mean 3%) of the observed indirect mutagenic activity could be explained. This implies that most mutagenic activity originated from other substances that were not identified or measured in our chemical analysis. This underscores the importance of bio-monitoring measurements.     

Structural determination of a directly mutagenic amino-nitrobiphenyl as the S9 metabolite of 2,4,2′,4′-tetranitrobiphenyl in Salmonella typhimuriumTA98

In order to elucidate the mechanisms of mutagenic activation of nitrobiphenyls by mammalian activation systems, 2,4,2′,4′-tetranitrobiphenyl was incubated with S9 and its mutagenic metabolites were separated by SiO₂ and Al₂O₃ column chromatography. The most mutagenic diamino-dinitrobiphenyl was isolated from the reaction mixture of 2,4,2′ ,4′-tetranitrobiphenyl with S9 mix at 37°C for 48 h, and its mutability was 4646 revertants/50 ng in Salmonella typhimurium TA98 without S9 mix. The deamination product of this most mutagenic metabolite was identical to 2,4′-dinitrobiphenyl by gas chromatography-mass spectrometry. Therefore, the structure of the metabolite was determined as 2,4′-diamino-2′,4-dinitrobiphenyl by its chemical and physico-chemical properties.