Inhibition of mutagenic N-nitroso compound formation in sausage samples by using l-ascorbic acid and α-tocopherol

In this study 24 samples of sausage with different amounts of nitrite, l-ascorbic acid and α-tocopherol were prepared in order to determine the inhibitory effects of l-ascorbic acid and α-tocopherol as reductants against formation of mutagenic N-nitroso compounds that form in cured meat products. These mutagenic N-nitroso compounds were extracted by phosphate buffer and ethylacetate. The mutagenicity of extracts were investigated by salmonella/microsome assay. The number of revertants indicated the N-nitroso compounds content. Among the Salmonella typhimurium strains tested, the revertants of S. typhimurium TA100 were significantly reduced (P<0.5) by 60% when reductants were added to the samples.     

Studies on the mutagenicity of aniline in association with norharman in the Salmonella/mammalian microscome assay

The mutagenicity of aniline was investigated in association with norharman using Aroclor 1254–induced and uninduced liver S9 fractions. The non-mutagenicity of aniline in the Salmonella /mammalian microsome test was also re-examined under various experimental conditions. Aniline caused no increase in the number of revertants per plate in Salmonella typhimurium strains TA1535, TA100, TA1537, TA1538 and TA98 at concentrations of up to 5000 μg/plate. S9 preparations from rat liver, hamster liver, rat spleen, or hamster spleen were all ineffective in activating aniline to a mutagen in tests using various concentrations of S9 in S9 mix. In contrast to the results with aniline alone, mixtures of aniline and norharman were mutagenic in strain TA1538 in the presence of S9 fractions from liver of rats pretreated with Aroclor 1254. The observed mutagenicity decreased as a function of the concentration of S9 in S9 mix. In the presence of uninduced liver S9 preparations, the mutagenicity of the mixture of the two compounds was slight (three-fold).     

Studies on antimutagenic effect of milk cultured with lactic acid bacteria on the Trp-P2-induced mutagenicity to TA98 strain of Salmonella typhimurium.

The inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82.1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, Lll103 (10-3) and Lll102 (KM) also exhibited higher inhibition percentages.     

Mutagenicity and Safety Evaluation of Water Extract of Fermented Toona Sinensis Roemor Leaves

ABSTRACT:  The purpose of this study was to evaluate the mutagenicity and safety of water extract of fermented Toona sinensis Roemor leaves (WFTS). The WFTS was prepared by fermenting Toona sinensis Roemor leaves anaerobically for 14 d, and then extracting with boiling water. The mutagenic effects of WFTS were investigated using Ames test. No mutagenicity was found toward all tester strains ( Salmonella typhimurium TA98, TA100, TA102, TA1535). In the acute oral toxicity study, a single limit dose of 2.5 or 5 g/kg body weight (bw) WFTS was given to male Sprague-Dawley (SD) rats, then the rats were observed for 14 d. No acute lethal effect at a maximal dose of 5 g/kg bw WFTS was observed in rats. In the subacute study, the male rats were administered daily by gavage at a dose of 0.5 or 1 g/kg bw/d of WFTS for 28 d. The results indicated that no significant toxic effect was found in the parameters of body and organ weight, as well as hematological, biochemical, urinary, and pathological parameters between control and the WFTS-treated rats. The level of no observed adverse effect level (NOAEL) of WFTS in male rats was 1 g/kg bw for subacute toxicity study.     

Antimutagenicity of milk cultured with lactic acid bacteria against N-methyl-N'-nitro-N-nitrosoguanidine.

The antimutagenic effect of cultured milk using 71 strains of lactic acid bacteria belonging to the genus Lactobacillus, Streptococcus, Lactococcus, and Bifidobacterium on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine was investigated in vitro using Salmonella typhimurium TA 100 as an indicator bacterium. Each cultured milk sample displayed its characteristic antimutagenic effect on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine. The milk cultured with Lactobacillus acidophilus LA 106 (LA2) showed the highest inhibition of 77% against the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine among the strains tested. Changes in the antimutagenic effect of the milk cultured by Lb. acidophilus LA 106 (LA2) during incubation were also examined using N-methyl-N'-nitro-N-nitrosoguanidine as a mutagen.     

Mutagenicity evaluation of nitroanilines and nitroaminophenols in Salmonella typhimurium

In our studies of structure-activity relationships, three nitroanilines and nine nitroaminophenols were tested for their ability to induce mutations in Salmonella typhimurium strains TA1535, TA100, TA1537, TA1538 and TA98. The compounds m -nitroaniline, 4-nitro-2-aminophenol, and 3-nitro-6-aminophenol were active in two or more of these strains. The compounds o -nitroaniline, 2-nitro-3-aminophenol, 3-nitro-4-aminophenol, 4-nitro-3-aminophenol, 3-nitro-2-aminophenol, 2-nitro-6-aminophenol, 2-nitro-4-aminophenol and 2-nitro-5-aminophenol were inactive, both in the presence and in the absence of S9 mix. The compound p -nitroaniline was also inactive in all tests with the possible exception of that in strain TA98 in the presence of S9 mix, where it was either very weakly mutagenic or non-mutagenic. The mutagenic activity or inactivity of these compounds appears to be dependent on the positions of the amino, nitro, and hydroxy groups in their chemical structures.
Etude en mutagénèse des nitroanilines et nitroaminophénols sur Salmonella typhimurium .     

Isolation and characterization of some products of the BHA-nitrite reaction: examination of their mutagenicity

The reaction mixture and several products arising from the reaction of butylated hydroxyanisole (BHA) and nitrite in anaerobic aqueous acidic solution were separated and tested in the Salmonella mutagenicity test. Among the nine products separable by thin-layer chromatography, 1-hydroxyl-2-tert-butyl-4-methoxy-6-nitrobenzene (BHA-NO2), tert-butyl-substituted para-quinone (t-BuQ) and 3-tert-butyl-5-methoxy-1,2-benzoquinone (t-Bu-o-Q) are dominant. The last compound has not been previously reported in this system. Spot testing indicated at least one further compound of nitroso character and traces of tert-butylhydroquinone (t-BuHQ), which reacts with nitrite to yield t-BuQ. No evidence was found for the formation of the BHA dimer under our conditions. The substances gave no evidence of mutagenicity in the Salmonella typhimurium strains TA 98 and TA 100, either in the standard plate incorporation assay or in the procedure with preincubation with or without S9 mix. In some instances the substances were unstable in the test procedure.     

Modulation of the cytotoxicity and genotoxicity of the drinking water disinfection byproduct lodoacetic acid by suppressors of oxidative stress

Drinking water disinfection byproducts (DBPs) are generated by the chemical disinfection of water and may pose a hazard to the public health. Previously we demonstrated that iodoacetic acid was the most cytotoxic and genotoxic DBP analyzed in a mammalian cell system. Little is known of the mechanisms of its genotoxicity. The involvement of oxidative stress in the toxicity of iodoacetic acid was analyzed with the antioxidants catalase and butylated hydroxyanisole (BHA). lodoacetic acid toxicity was quantitatively measured with and without antioxidants in Salmonella typhimurium strain TA100 and with Chinese hamster ovary (CHO) cells. The endpoints included cytotoxicity in S. typhimurium or in CHO cells, mutagenicity in S. typhimurium, and genotoxicity in CHO cells. Neither catalase nor BHA reduced the level of iodoacetic acid induced cytotoxicity in S. typhimurium. In CHO cells neither antioxidant caused a significant reduction in iodoacetic acid induced cytotoxicity. However, in S. typhimurium, BHA or catalase reduced the mutagenicity of iodoacetic acid by 33.5 and 26.8%, respectively. Likewise, BHA or catalase reduced iodoacetic acid induced genomic DNA damage by 86.5 and 42%, respectively. These results support the hypothesis that oxidative stress is involved in the induction of genotoxicity and mutagenicity by iodoacetic acid.     

Antimutagenic activity of natural phenolic compounds present in the common bean ( Phaseolus vulgaris ) against aflatoxin B 1

Polyphenols with antimutagenic and anticarcinogenic properties are present in fruits, vegetables and legumes. In this study, the Salmonella typhimurium tester strains TA98 and TA100 were used in the microsuspension assay to examine the antimutagenic effect of phenolic compounds extracted from the common bean (Phaseolus vulgaris) against mutagenicity induced by aflatoxin B 1 (AFB 1 ). A dose-response curve was constructed for AFB 1 ; from which a level of 40ng AFB 1 /tube was selected for all antimutagenicity assays. The AFB 1 and phenolic extract (PE) were not toxic to the bacteria at concentrations tested. In the case of PE, results were similar to the number of spontaneous revertants for TA98 and TA100. The inhibitory effect of PE against AFB 1 mutagenicity was dose-dependent at the lower concentrations tested (2.5, 5, 10, 12.5, 15 and 25 μg-equivalent ( + )-catechin/tube for TA98; 0.5, 1, 1.5, 2.5, 5, 10 and 25 μg-equivalent ( + )-catechin/ tube for TA100). Further, a two-stage incubation procedure was used to investigate the potential interaction between PE and AFB 1 . The greatest inhibitory effect of the PE on AFB 1 mutagenicity occurred when PE and AFB 1 were incubated together. When the bacteria were first incubated with PE followed by a second incubation with AFB 1 , lower inhibition was observed. Lower inhibition was also observed when the bacteria were first incubated with AFB 1 followed by a second incubation with PE. The results suggest that the mechanism of inhibition could involve the formation of a chemical complex between of PE and AFB 1 .     

Change in mutagenicity in white rice after accelerated and long-term storage

ABSTRACT:  Certain reactions that occur in food during storage, such as nonenzymatic browning and lipid oxidation, form compounds that have been shown to be mutagenic. It is possible that over long storage periods, significant amounts of these products could be formed. Although some research has been published concerning the mutagenicity of foods due to processing or cooking, little research has been done regarding mutagenicity of foods stored for an extended time. The objective of this research was to determine the potential mutagenicity of white rice held in accelerated and long-term storage using the Ames Salmonella /microsome assay. Fresh long-grain white rice was packaged in foil laminate pouches and held at 60 °C for 18 wk. Rice stored for > 25 y in an oxygen-free environment at or below room temperature in size number 10 cans was obtained from residential storage. The standard plate-incorporation method was used to evaluate the mutagenic potential of all treatments using Salmonella typhimurium tester strains TA97a, TA98, TA100, and TA102. Samples were plated at 5 dilutions with and without rat liver S9 enzyme. A solvent control was also plated for each strain. Treatments yielding counts at least double the solvent control level were considered mutagenic. Plate counts for all treatments fell well below the required doubling of the solvent control value. White rice held in accelerated and long-term storage appears not to increase in mutagenic compounds as measured by the Ames assay, supporting its use for long-term storage purposes such as emergency preparedness and humanitarian food aid.     

MUTAGENICITY OF HEATED COTTONSEED FRYING OIL

A control experiment showed that cottonseed oil used in frying falafel developed significant mutagenic activity. As a result, one hundred samples of fresh and used cottonseed oil employed commercially for frying falafel were collected from restaurants in thirteen major cities of Egypt. Samples were examined for mutagenic activity using the Salmonella typhimurium assay with and without S9. Six of the heated oil samples showed significant mutagenic activity. None of the fresh unheated oil samples were mutagenic. Salmonella typhimurium TA 102 gave a higher response than did either TA 100 or TA 98.
Peroxide, hydroxyl, acid and conjugated diene values were much higher for mutagenic samples. Iodine values, however, were lower. Liquid chromatography fractionation revealed that the mutagenicity was concentrated in the polar fraction. The column fraction having the highest mutagenic activity was further examined by chromatographic and spectroscopic techniques.     

Metabolic activation and inactivation of metanil yellow and orange II in the Salmonella typhimurium his-reversion assay.

Among a variety of experimental protocols used, the combined use of 0.5% dextrose in bottom agar and 1 micromol of flavin mononucleotide (FMN) in preincubation mixtures without fraction S9 mix resulted in the highest level of induced Salmonella typhimurium his reversions with both dyes metanil yellow and orange 11 with strain TA100. Strain TA98 yielded notably lower levels of reversions under the same conditions. The presence of uninduced hamster liver S9 fraction resulted in a weak mutagenic response while Aroclor 1254-induced rat liver S9 fraction resulted in the complete absence of mutagenicity with both strains and with both dyes.     

2-Dodecylcyclobutanone does not induce mutations in the Salmonella mutagenicity test or intrachromosomal recombination in Saccharomyces cerevisiae

Treatment of foods, such as red meat and poultry, that contain palmitic acid with ionizing radiation leads to the formation of 2-dodecylcyclobutanone (2-DCB), a compound found only in irradiated foods. In this study, the Salmonella mutagenicity test and the yeast DEL assay were used to evaluate the genotoxic potential of 2-DCB. Salmonella Typhimurium tester strains TA98, TA100, TA1535, and TA1537 were exposed to 0, 0.125, 0.25, 0.5, and 1 mg per well of 2-DCB, with and without exogenous metabolic activation (5% S9 fraction), using the microtiter plate-based Miniscreen version of the test. 2-DCB did not induce mutations in the Salmonella mutagenicity test. When Saccharomyces cerevisiae strain RS112, which contains a nonfunctional duplication of the his3 gene that can be induced to form a functional HIS3+ gene by intrachromosomal recombination, was exposed to 0.63, 1.25, 2.5, or 5.0 mg/ml of 2-DCB, no increase in the rate of intrachromosomal (DEL) recombination was observed. The absence of genotoxicity observed in this study using purified 2-DCB agrees with the lack of genotoxic and teratogenic activity observed in previously conducted multigeneration feeding studies of laboratory animals (rats, mice, guinea pigs, and rabbits) that used radiation-sterilized poultry that contained 2-DCB as a unique radiolytic product.     

NNK和B[a]P在卷烟烟气基质中的联合致突变性

以苯并[a]芘(B[a]P)、甲基亚硝胺吡啶基丁酮(NNK)为目标化合物,设置卷烟烟气冷凝物(CSC)的浓度为0(CK),0.005,0.010,0.015,0.020 mg/mL;NNK的浓度为0(CK),0.005,0.010,0.020,0.040 mg/mL;B[a]P的浓度为0(CK),0.00025,0.00050,0.00075,0.00100 mg/mL,研究了NNK,B[a]P和CSC的联合致突变性。结果表明:①CSC,NNK和B[a]P均可诱导鼠伤寒沙门氏菌TA98,TA100发生突变,且剂量-效应明显。②B[a]P与CSC联合呈相加作用;B[a]P与NNK联合高剂量呈弱相加作用;CSC与NNK联合低剂量呈弱相加作用。③在不同情况下,三者联合作用致TA98呈弱相加作用。综上,NNK和B[a]P在卷烟烟气基质中的联合致突变性呈现量效、时效和先后作用顺序的复杂性。     

Rapid selection of nonhotspot mutants among hisD+ revertants of Salmonella typhimurium TA98 in Ames test by peptide nucleic acid (PNA)-mediated PCR clamping

Ames test is the most popular method of assessing mutagenicity using Salmonella typhimurium as an indicator. Recently, sequence analyses have been introduced for the investigation of mutation mechanisms. Most revertants (>70%) carry 2-bp deletion within an 8-bp CG repeat in hisD (hotspot mutation) in the Ames test using S. typhimurium TA98. We developed a new specific amplification method for nonhotspot mutants by peptide nucleic acid (PNA)-mediated PCR clamping. It markedly reduces the labor and cost of this kind of studies.     

Mutagenicity and Identification of the Reaction Products of Aqueous Chlorine or Chlorine Dioxide with L-Tryptophan

Nonvolatile products generated from reactions of graded molar ratios of aqueous chlorine or chlorine dioxide with L-tryptophan (1:1, 3:1 and 7:1) were shown to be direct-acting mutagens to Salmonella typhimurium TA100 and TA98. Increasing the ratio of disinfectant relative to amino acid led to increased mutagenic activity, with mutagenicity highest at the 7:1 molar ratio. Several fluorescent bands obtained after thin layer chromatographic fractionation of the reaction mixtures were shown to be more mutagenic than the reaction mixtures. GC/MS analysis of the compounds in a highly mutagenic fraction of the aqueous chlorine reaction products identified 1,1,3-trichloropro-panonc, 1,1,3,3-tetrachloropropanone and dichloroquinoline.     

Evaluation of mutagenic and antimutagenic activities of oligorutin and oligoesculin

Rutin and esculin have been polymerised by laccase. Five fractions with M(w)ˉ between 2127.42 and 8331.85g/mol for oligorutins, and between 688.12 and 6973g/mol for oligoesculins, were obtained. Fourier transformed infrared analysis showed that oligorutins were formed through C-C, C-O and CO linkages, while oligoesculins were obtained through C-C linkages. Monomers, their oligomers and their metabolites exhibited no mutagenic effect. Oligorutins and oligoesculins were more efficient in reducing the mutagenicity of methyl methanesulphonate, by, respectively, 69% and 64.8% in the presence of Salmonella typhimurium TA104, and 79.7% and 68.9% in the presence of S. typhimurium TA102, than were their monomers. The same oligomers revealed greater significant inhibitory effect of 2-aminoanthracene mutagenicity (respectively 82.4% and 79.3% in the presence of S. typhimurium TA104, and 89.2% and 82.9% in the presence of S. typhimurium TA102), than their monomers. Our results strongly suggest the enhancement of the tested monomer antimutagenicity after polymerisation.     

N-nitrosamine and mutagenicity formation in Chinese salted fish after digestion.

Salted and dried fish (Nemipterus virgatus), acquired from Hong Kong, was treated with 0.43-110 mM nitrite during in vitro digestion using gastric enzymes and the volatile N-nitrosamine content and mutagenicity on Salmonella typhimurium TA100 assayed without concentration. N-Nitrosodimethylamine (NDMA; the only nitrosamine detected) formation was second order in nitrite concentration. When 10 g of fish was treated with 6.96 mM nitrite, 394 nM NDMA was formed. Thiocyanate was catalytic for NDMA formation at nitrite concentration greater than 0.87 mM and when the ratio of thiocyanate to nitrite was greater than 1. Approximately a 50% inhibition in NDMA formation by ascorbic acid was seen when the ratio of ascorbate to nitrite was approximately 2 or greater and the nitrite concentration was 1.74 mM. Mutagenicity increased with increasing nitrite concentration but the addition of thiocyanate did not increase mutagenicity over nitrite alone. Ascorbate increased mutagenicity even though NDMA formation was inhibited. Even at nitrite concentrations greater than 100-fold higher than expected in vivo, there was insufficient NDMA formed to account for the observed mutagenicity. These data do not exclude the possibility that the observed mutagenicity was due to non-volatile N-nitroso compounds, however, this possibility seems unlikely given the effects of ascorbate and thiocyanate which would be expected to inhibit and enhance non-volatile N-nitroso compound formation.     

Inhibitory effects of water extract from longan twigs on mutation and nitric oxide production

This study examines the inhibitory effects of water extract from longan twigs (WLTs) on mutation and nitric oxide (NO) production. The results show that WLT inhibited the mutagenicity of 2-aminoanthracene (2-AA), an indirect mutagen, and 4-nitroquinoline-N-oxide (4-NQO), a direct mutagen toward Salmonella typhimurium TA 98 and TA 100. In addition, WLT in the range 0-0.6 mg/ml showed radical scavenging, reducing activities and chelating activity, as well as decreased lipid oxidative damage. Meanwhile, WLT also inhibited tyrosinase activity and NO generation in lipopolysaccharide (LPS) stimulated macrophages. High performance liquid chromatography analysis suggests that the major phenolic constituents in WLT are epicatechin, ellagic acid and gallic acid. These bioactive components may contribute to the protective effects of WLT. Our data suggests that WLT can be applied to antimutation, anti-inflammation and antityrosinase.     

Reactions of Aqueous Chlorine and Chlorine Dioxide with Tryptophan, N-Methyltryptophan, and 3-Indolelactic Acid: Kinetic and Mutagenicity Studies

Reactions of tryptophan, N-methyltryptophan and 3-indolelactic acid with aqueous chlorine or chlorine dioxide (ClO₂) in 0.1M potassium phosphate buffer, pH 6.0, were investigated to determine any structural relationships with regards to kinetics and mutagenicity. The reaction with ClO₂ followed pseudo-first order kinetics, with the half-life of the respective compounds being 36, 22, and 8 milliseconds. The formation of a dark precipitate in the reaction of tryptophan with HOCl precluded any kinetic comparison. The reaction products of tryptophan with hypochlorous acid (HOCl) or ClO₂ were mutagenic to Salmonella typhimurium TA98 and TA100; while those of N-methyltryptophan with HOCl and ClO₂ were more mutagenic toward TA98. Higher recoveries of the reaction products were achieved by passing the acidified (pH 2.5) mixture through an XAD-8/XAD-2 resin column.