Suppression of mutation induction and failure to detect mutagenic activity with athabasca tar sand fractions.

5 different histidine-requiring strains of Salmonella typhimurium were used to test the mutagenic activity of 7 different fractions of Athabasca tar-sand. None of the 7 fractions (bitumen, maltenes, asphaltenes, saturated, monoaromatic, diaromatic and polyaromatic hydrocarbons), showed positive mutagenic response in any of the Salmonella typhimurium strains. We have tested a wide range of concentrations. The results obtained so far are consistent with the lack of mutagenic activity of all investigated fractions in the absence and in the presence of metabolic activation. Assuming that there might be an association between the absence of mutagenic activity and the complexity of the tar-sand fractions, we investigated the effect of the polyaromatic hydrocaron fraction on the mutagenicity of the carcinogenic agent 2-aminoanthracene. The data obtained indicate clearly that the polyaromatic hydrocarbon fraction suppresses the mutagenic activity of 2-aminoanthracene.     

The mutagenic activity of 4-chloromethylbiphenyl (4CMB) and Benzyl Chloride (BC) in the bacterial/microsome assay

The mutagenic activity of 4CMB was investigated in agar layer cultures of Salmonella typhimurium TA1535, TA1537, TA1538, TA98 and TA100, and Escherichia coli WP2 and WP2 uvrA. The mutagenic activity of BC was investigated in the Salmonella strains only. Assays were performed both in the absence and in the presence of S9 microsomal fraction obtained from a liver homogenate from rats pretreated with Aroclor 1254.     

Mutagenicity of five food additives in Ames/Salmonella/microsome test

The mutagenic activity of five food additives (K₂S₂O₅: potassium metabisulphite, KMB; K₂SO₄: potassium sulphate, KS; Na₂SO₃: sodium sulphite, SS; KNO₃: potassium nitrate, KN; NaNO₃: sodium nitrate, SN) were investigated using histidin auxotrophs TA98 and TA100 strains ofSalmonella typhimurium in the presence or absence of S9 mix. The test substance were investigated for their mutagenic effects at non toxic concentrations of 0.83, 1.66, 3.33 and 5.00 mg/plate with and without S9 mix. All the test substances were not mutagenic on TA98 and TA100 strains ofSalmonella typhimurium in the presence or absence of S9 mix except KS and SN. KS and SN showed a weak mutagenic effect on TA100 strain in the absence of S9 mix.     

Mutagenic evaluation of the monocyclic aromatic amine N-methylamino-2-nitro-4-N′,N′-bis(2-hydroxyethyl)aminobenzene in the Salmonella typhimurium/mammalian microsome test

The hair-dye component N-methylamino-2-nitro-4-N′,N′-bis(2-hydroxyethyl)aminobenzene was investigated for mutagenic activity in Salmonella typhimurium strains TA1535, TA100, TA1537, TA1538 and TA98. The testing was performed in the absence and in the presence of a rat-liver microsomal activation system induced by Aroclor 1254. Our results indicate that N-methylamino-2-nitro-4-N′,N′-bis(2-hydroxyethyl)aminobenzene does not induce mutations in Salmonella typhimurium strains, either in the absence or in the presence of the metabolic activation system. The purity of the compound was controlled by utilizing high-pressure liquid chromatography (HPLC) and thin-layer chromatography (TLC).     

Mutagenicity of alkylhydrazine oxalates in Salmonella typhimurium TA100 and TA102 demonstrated by modifying the growth conditions of the bacteria

Alkylhydrazines are important carcinogens. However, they show generally only weak mutagenicity and the activities reported from different laboratories are contradictory. We have developed a sensitive method to detect the mutagenicity of alkylhydrazines. The method is based on a modified preculturing procedures in the Ames test, the emphasis in the modification being a change in the growth period of tester strains. The optimal growth periods were found to be 11 h in Salmonella typhimurium TA100 and 5 h in Salmonella typhimurium TA102. We tested the mutagenic activity of 12 alkylhydrazines; 1,2-dimetehylhydrazine, 1,2-diethylhydrazine, 1,2-dipropylhydrazine. 1,2-dibutylhydrazine, 1,1-dimethylhydrazine, 1,1-diethylhydrazine, 1,1-dipropylhydrazine, 1,1-dibutylhydrazine, methylhydrazine, ethylhydrazine, propylhydrazine, and butylhdyrazine. All 12 alkylhydrazines were clearly mutagenic in Salmonella typhimurium TA102, and 10 hydrazines were mutagenic in Salmonella typhimurium TA100, both in the absence of S9 mix. The mutagenicity was inhibited by the addition of S9 mix or bovine serum albumin. This suggests deactivation of the mutagens by proteins.     

Comparison of the sensitivity of Salmonella typhimurium strains YG1024 and YG1012 for detecting the mutagenicity of aromatic amines and nitroarenes

Salmonella typhimurium YG1024 is a derivative of S. typhimurium TA98 with a high level of N-hydroxyarylamineO-acetyltransferase (OAT) activity. We have demonstrated that this strain is highly sensitive to the mutagenic actions of N-hydroxyarylamines derived from aromatic amines and nitroarenes. In this paper, we compared the sensitivities of YG1024 with those of S. typhimurium YG1012, which has about 4 times higher OAt activity than YG1024 but lacks plasmid pKM101. It turned out that YG1024 was more sensitive to the mutagenic actions of 1-aminonaphthalene, 1-nitropyrene, 1,8-dinitropyrene and 2-nitronaphthalene than YG1012 and showed comparable sensitivity to 2-hydroxyacetylaminofluorene, 2-aminoanthracene and 2-amino-6-methyldipyridol[1,2-α:3′,2′-d]imidazole (Glu-P-1) to YG1012. These results suggested that YG1024 is more suitable than YG1012 for the efficient detection of mutagenic aromatic amines and nitroarenes.     

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.     

Mutagenicity assessment of Salacia chinensis by bacterial reverse mutation assay using histidine dependent Salmonella typhimurium tester strains

Background and objectiveGenotoxicity analysis is one of the most important non-clinical environmental safety investigations required for pharmaceutical and agrochemical product registration. Any medicinal product must undergo a risk evaluation to determine its mutagenicity and carcinogenicity.Materials and methodsThe Ames test is a commonly used in vitro test for determining a test chemical's mutagenic activity. Histidine-dependent Salmonella typhimurium strains with a defective gene that causes the bacteria to synthesis the necessary amino acid histidine for life were tested for mutagenic potential. In order to reveal pro-mutagens and mutagens, the mutagenic potential of both plate integration and pre-incubation techniques was examined in the presence and absence of metabolizing system. Salacia chinensis has been widely used in ayurveda to treat various ailments. However, the information of mutagenicity of Salacia chinensis is scarce as per available literature.ResultsThe mutagenicity of a Salacia chinensis root extract was investigated utilizing the Ames assay with plate incorporation and pre-incubation protocols using the appropriate Salmonella typhimurium tester strains: TA98, TA100, TA1537, TA1535, and TA102 in the presence and absence of S9. The concentrations used were 0.3123, 0.625, 1.25, 2.5 and 5 mg/plate. The extract of Salacia chinensis root did not show any mutagenic effect in any of the Salmonella typhimurium strains at the concentrations tested in the absence or presence of metabolic activation.ConclusionThe root of Salacia chinensis was hence confirmed to be non-mutagenic and at least according to the results of this genotoxicity evaluation can be regarded as being safe for human use.     

Structural specificity of aromatic compounds with special reference to mutagenic activity in Salmonella typhimurium — a series of chloro- or fluoro-nitrobenzene derivatives

The mutagenicity of 21 chloro- or fluoronitrobenzene compounds and 9 chloro- or fluorobenzene compounds in Salmonella typhimurium (strains TA98, TA1538, TA1537, TA100 and TA1535) was examined. The tests were carried out under the conditions of absence and presence of liver microsomal activation.15 nitro-group compounds had mutagenic activity; above all, compounds of fluoronitrobenzene were mutagenic for both types of strain. On the other hand, chloronitrobenzene compounds were mutagenic for base-pair substitution strains only. Mutagenic activity was exhibited by all compounds having a chloro or fluoro substituent at the para and ortho position in the nitrobenzene nucleus. All compounds without a nitro substituent showed no mutagenic activity.     

Isolation and studies of the mutagenic activity in the Ames test of flavonoids naturally occurring in medical herbs

Quercetin, rhamnetin, isorhamnetin, apigenin and luteolin were isolated from medicinal herbs: Erigeron canadensis L., Anthyllis vulneraria L. and Pyrola chloranta L. The mutagenicity of these naturally occurring flavonoids was tested by the Ames method with S. typhimurium strains TA1535, TA1538, TA97, TA98, TA100 and TA102 in the presence and absence of metabolic activation. Of the above flavonoids only quercetin and rhamnetin revealed mutagenic activity in the Ames test. Quercetin induced point mutations in strains TA97, TA98, TA100 and TA102 of S. typhimurium. The presence of S9 rat liver microsome fraction markedly enhanced the mutagenic activity of quercetin in these strains. Rhamnetin appeared to be a much weaker mutagen in the Ames test. The compound induced mutations in strains TA97, TA98 and TA100 of S. typhimurium but only in the presence of metabolic activation.Comparison of the structure of the studied flavonoids with their mutagenic activity indicates that the mutagenicity of flavonoids is dependent on the presence of hydroxyl groups in the 3′ and 4′ positions of the B ring, and that the presence of a free hydroxy or methoxy group in the 7 position of the A ring also probably contributes to the appearance of mutagenic activity of flavonoids in the Ames test. It also appeared that the presence of methoxy groups, particularly in the B ring of the flavonoid molecule, markedly decreases the mutagenic activity of the compound.     

Effects of the hepatic S9 fraction from aroclor-1254-treated rats on the mutagenicity of benzo[a]pyrene and 2-aminoanthracene in the salmonella/microsome assay

The mutagenicity of benzo[a]pyrene and 2-aminoanthracene for Salmonella typhimurium TA98 in the plate-incorporation test was studied using liver S9 from untreated and Aroclor-1254-treated rats. The induction of liver S9 protein, arylhydrocarbon hydroxylase (AHH), and cytochrome P448/450 was followed with time. There was no change in protein concentrations with induction; AHH and cytochrome levels were increased at 1, 3, 5 and 7 days post Aroclor treatment. Benzo[a]pyrene mutagenicity was enhanced with Aroclor treatment while 2-aminoanthracene mutagenicity was depressed. The benzo[a]pyrene mutagenicity showed a positive correlation with the levels of AHH and cytochrome on the plate; 2-aminoanthracene showed a negative correlation with activity in induced samples.     

Lack of Mutagenicity of the Fungicide 2,4,5,6-Tetrachloroisophthalonitrile in the Ames Salmonella/Microsome Test

The fungicide 2,4,5,6-tetrachloroisophthalonitrile was found to be not mutagenic to five Salmonella typhimurium tester strains. Incorporation of either a liver or a kidney activation system did not increase the mutagenic activity of the fungicide.     

Mutagenic activities of ten imidazole derivatives in <Emphasis Type="Italic">Salmonella typhimurium</Emphasis>

Ten imidazole derivatives were tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100 both in the absence and presence of metabolic activation by the microsomal fraction S9 mix. In a general manner, derivatives tested exhibited a greater mutagenic activity in the TA100 strain comparing to the responses in TA 98. In the standard plate incorporation assay, 8 of these substances (80%) were found to be mutagenic for at least one of the two strains in the presence or absence of metabolic activation. Two compounds showed positive results in TA98 and 6 compounds were also mutagenic in TA100 without S9. In the presence of S9 mix, all of the 10 substances were non-mutagenic in TA98, whereas 4 compounds were positive in TA100. The results suggested the mutagenic potentials of the imidazole derivatives particularly inducing the reversion of base-pair substitutions. According to the structure-activity relationships phenyl groups in position 2 with different substituents can confer the mutagenic activity of the tested compounds. Methyl groups in different positions of these phenyl substituents can cause different types of mutations. This mutagenic effect is observed more clearly when the phenyl group is inhibited with a nitro group.     

Absence of mutagenic activity of benorylate,paracetamol and aspirin in the Salmonella//mammalian microsome test

Benorylate and its two major hydroyssis products, paracetamol and aspirin were examined for mutagenicity in the Salmonella/mammalian microsome screening test. The compounds were tested in 6 strains of Salmonella typhimurium (TA1535, TA1537, TA1538, TA100, TA97 and TA98) in the presence and absence of a rat-liver microsome activation system. Benorylate did not show evidence of mutagenic activity in the 6 strains tested with or without metabolic activation at concentrations ranging from 0.006 to 3 mg per plate. Paracetamol and aspirin likewise did not show any evidence of mutagenic activity at concentrations ranging from 0.1 to 50 mg per plate for the former and 0.01 to 50 mg per plate for the latter.     

Studies on the oxidation products from 2,4-diaminotoluene by hydrogen peroxide and their mutagenicities. II.

2,4-Diaminotoluene (DAT) was reacted with hydrogen peroxide at room temperature for 2 days, and the resulting red precipitates were separated into 5 fractions on silica gel column chromatography. On the gas chromatographic (GC) study, the first fraction (Fr. 1), which is mutagenic (1425 and 1391 revertants/μg in the absence and presence of S9 respectively) in Salmonella typhimurium TA98, contained several peaks. Fr. 1 was further separated into 4 subfractions (Fr. 1-I-Fr. 1-IV) by silica gel column chromatography. The red crystals were separated from Fr. 1-III and the structure of the compound was determined to be 1,8-diamino-2,7-dimethylphenazine from physicochemical and chemical evidence.Further, o-nitro-p-toluidine, p-nitro-o-toluidine, 3,3′-diamino-4,4′-dimethylazobenzene and 3,3′ diamino-4,4′-dimethylazoxybenzene were identified with authentic and synthesized samples by gas chromatography/mass spectrometry. These compounds without nitrotoluidines were mutagenic, and phenazine, azo and azoxy compounds induced 49, 301 and 245 revertants/nmole in Salmonella typhimurium TA98 with 25 μl S9 per plate, respectively.     

Application of the Salmonella typhimurium microsome test to the study of 25 drugs belonging to 5 chemical series

25 active-principle forms of pharmaceutical drugs belonging to 5 chemical series have been tested for mutagenic activity. To screen these drugs we used the Salmonella typhimurium assay on 5-histidine-requiring strains, with and without microsomal activation. Only the 3 nitroimidazole derivatives were mutagenic for strains TA100, TA1535 and TA98.     

Activation of benzo[a]pyrene and 2-aminoanthracene to bacteria mutagens by mussel digestive gland postmitochondrial fraction

The ability of the mussel postmitochondrial fraction (S9) to activate benzo[a]pyrene (BaP) and 2-aminoanthracene (2AA) to mutagenic metabolites towards Salmonella typhimurium strain TA98 was tested. The mechanisms involved in this activation were investigated and mussel cytochrome P-450-dependent monooxygenases and its NADPH cytochrome c reductase were found to contribute to the activation of BaP. This activation was improved by treating the mussel with 4,5,4′,5′-tetrachlorobiphenyl (TCB) (a 3-methylcholanthrene-type inducer of cytochrome P-450-dependent monooxygenase in marine fish) and was inhibited by α-naphthoflavone (ANF), a cytochrome P-450 inhibitor. However, both BaP activation and cytchrome P-450-related metabolic activities are much weaker in mussels than in vertebrates. Mussel S9 activates aromatic amines more effectively than BaP. Pretreatment of mussels with TCB or addition of ANF in the incubation medium has no effect on 2AA activation. As suggested by Kurelec (1985), aromatic amine metabolism may be supported by a flavoprotein mixed-function amine oxidase which is NADPH-dependent.     

Mutagenicity of styrene and styrene oxide

Incubation of S. typhimurium strain TA 1535 with styrene increased the number of his⁺ revertants/plate in presence of a fortified S9 rat-liver fraction. Styrene was also highly cytotoxic for Salmonella cells. Styrene oxide, the presumed first metabolite, had a mutagenic effect towards strains TA 1535 and TA 100 both with and without metabolic activation. Styrene is probably mutagenic because it is metabolized to styrene oxide.     

Antibacterial and cytotoxic activities of extracts from (Tunisian)Rhamnus alaternus (Rhamnaceae)

The petroleum ether, chloroformic, ethyl acetate, methanolic, Total Oligomers Flavonoids (TOF) enriched extracts, water extract as well as its fractions A₁, A₂, A₃ obtained from aerial parts ofRhamnus alaternus, a Tunisian-Mediterranean medicinal species, were investigated for the contents of phenolic compounds, cytotoxic activity against the K562 human chronic myelogenous leukaemia cell line and L1210 leukaemia murine cells and for antibacterial activity against Gram positive and Gram negative bacterial reference strains. A pronounced cytotoxic effect on both the cell lines was shown in the TOF, ethyl acetate, methanolic, aqueous extracts and A₂ fraction, with respectively IC₅₀ values 75, 232, 298, 606 and 571 μg/ml on K562 cells and 198, 176, 767, 560 and 614 μg/ml on L1210 cell line. Significant activity against bacterial reference strains:Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Salmonella enteritidis andSalmonella typhimurium was shown with ethyl acetate, TOF extracts and A2 fraction. The antimicrobial and cytotoxic activities showed byR. alatemus depended on the chemical composition of the tested extracts.     

Mutagenicity of methylated fluorenes and benzofluorenes

Methylated fluorenes were assayed for mutagenic activity towards Salmonella typhimurium TA98 and TA100. None of these methylfluorenes were mutagenic in the absence of metabolic activation. In the presence of 900 × g supernatant from Aroclor-induced rats, 9-methylfluorene and 1,9-dimethylfluorene were active towards TA98 and TA100. The structural requirement for mutagenic activity within this series was the presence of a single methyl substituent at the 9-position. Enhanced mutagenic activity was also observed for benzofluorenes similarly methylated at their benzylic positions.