Short Communication: Ames assay with Salmonella typhimurium TA102 for mutagenicity and antimutagenicity of metallic oxide powders having antibacterial activities

Metallic oxide powders (magnesium oxide, calcium oxide and zinc oxide) having antibacterial activity were examined for their mutagenicity and antimutagenicity by the Ames test with Salmonella typhimurium TA 102. These powders were not mutagenic to the tester strain and reduced the mutagenicity of methylglyoxal.     

The antimutagenic effect of selenium on 7,12-dimethylbenz(a)anthracene and metabolites in the amesSalmonella/microsome system

The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene, and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na₂SeO₃ reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion. Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na₂SeO₄ inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that form and concentration are important factors in this trace element's efficacy.     

Experimental databases on inhibition of the bacterial mutagenicity of 4-nitroquinoline 1-oxide and cigarette smoke

Two antimutagenicity databases were prepared by applying a co-treatment procedure to the Salmonella reversion assay. Ninety compounds belonging to various chemical classes were quantitatively tested for antimutagenicity towards the direct-acting mutagen 4-nitroquinoline 1-oxide (4NQO) in strain TA100 of S. typhimurium and 63 of them were additionally tested for antimutagenicity towards unfractionated mainstream cigarette smoke (CS) in strain TA98, in the presence of S9 mix. Twelve compounds (13.3%) inhibited 4NQO mutagenicity by at least 50%, with a MID₅₀ (dose inhibiting 50% of mutagenicity) varying over a 1226-fold range. Twenty-six compounds (41.3%) inhibited CS mutagenicity, with a MID₅₀ varying over a 520-fold range. Three compounds only, i.e., bilirubin, curcumin and myricetin, were capable of inhibiting the mutagenicities of both 4NQO and CS. However, myricetin and the other flavonoid rutin were at the same time mutagenic by inducing frameshift mutations following metabolic activation. There was a rather rigorous selectivity of antimutagenicity data depending on the chemical class of inhibitors and it was possible to discriminate protective effects within several pairs or series of structurally related compounds. For instance, all eight thiols and aminothiols inhibited 4NQO mutagenicity, which contrasted with the inactivity of the remaining 17 sulfur compounds tested, all of them lacking a free sulfhydryl group. The mutagenicity of CS was consistently inhibited by the majority of phenols (eight out of 10 tested) and by all two isothiocyanates, two dithiocarbamates, three indole derivatives, three tetrapyrrole compounds and three flavonoids tested. Although the results obtained cannot be extrapolated to other mutagens or test systems, they may provide a useful source of information for research in the area of antimutagenesis and for the development of chemopreventive agents.     

Assessment of the relationship between the antimutagenic action of riboflavin and glutathione and the levels of antioxidant enzymes

In this study the role of antioxidant enzymes on the antimutagenic actions of riboflavin and reduced glutathione against mutagenic potentials of 4-nitroquinoline 1-oxide and mitomycin C have been investigated. For this purpose the activities of catalase and superoxide dismutase enzymes have been determined in Salmonella typhimurium TA102 and TA100 strains preincubated with different combinations of 4-nitroquinoline 1-oxide, mitomycin C, riboflavin and reduced glutathione for thirty minutes. Also in part of the same samples, the mutagenicity has been determined for each combination of chemicals by using Salmonella preincubation test. The correlation between the levels of antioxidant enzymes and mutagenicity and antimutagenicity has been investigated.While riboflavin displayed a weakly antimutagenic effect on 4-nitroquinoline 1-oxide mutagenicity in TA102 and TA100 (0.25, 0.35 inhibition respectively), it did not have any effect on the strong mutagenicity of mitomycin C in both strains. Reduced glutathione, a well known antioxidant, had no antimutagenic effect against the mutagenicity of both compounds in TA102 and TA100 strains. The antioxidant enzymes, catalase and superoxide dismutase, seemed to have no direct effect on the antimutagenic action of riboflavin and mutagenic action of 4-nitroquinoline 1-oxide and mitomycin C because no change in the activities of catalase and superoxide dismutase was detected in relation to antimutagenicity of riboflavin and mutagenicity of 4-nitroquinoline 1-oxide and mitomycin C in both strains. It should be noted that many antimutagens have more than one mechanism of action and their effect depends on the mutagens being tested.     

Evaluation of mutagenic and antimutagenic properties of some bioactive xanthone derivatives using Vibrio harveyi test

Aims: Drug safety evaluation plays an important role in the early phase of drug development, especially in the preclinical identification of compounds’ biological activity. The Vibrio harveyi assay was used to assess mutagenic and antimutagenic activity of some aminoalkanolic derivatives of xanthone (1–5), which were synthesized and evaluated for their anticonvulsant and hemodynamic activities. Methods and Results: A novel V. harveyi assay was used to assess mutagenic and antimutagenic activity of derivatives of xanthone 1–5. Two V. harveyi strains were used: BB7 (natural isolate) and BB7M (BB7 derivative containing mucA and mucB genes on a plasmid pAB91273, products of these genes enhance error‐prone DNA repair). According to the results obtained, the most beneficial mutagenic and antimutagenic profiles were observed for compounds 2 and 3. A modification of the chemical structure of compound 2 by the replacement of the hydroxy group by a chloride improved considerably the antimutagenic activity of the compound. Thus, antimutagenic potency reached a maximum with the presence of tertiary amine and chloride atom in the side chain. Conclusions: Among the newly synthesized aminoalkanolic derivatives of xanthone with potential anticonvulsant properties, there are some compounds exhibiting in vitro antimutagenic activity. In addition, it appears that the V. harveyi assay can be applied for primary mutagenicity and antimutagenicity assessment of compounds. Significance and Impact of the Study: The obtained preliminary mutagenicity and antimutagenicity results encourage further search in the group of amino derivatives of xanthone as the potential antiepileptic drugs also presenting some antimutagenic potential. Furthermore, V. harveyi test may be a useful tool for compounds safety evaluation.     

Antimutagenic effect of heteroxylans,arabinogalactans, pectins and mannans in the Euglena assay

A series of plant cell wall polysaccharides – heteroxylans, arabinogalactans, pectins and mannans exerted antimutagenic (antibleaching) activity against acridine orange- and ofloxacin-induced mutagenicity in the Euglena assay. All polysaccharides tested exhibited a significant dose-dependent antibleaching activity and the percentage inhibition of mutagenicity ranged from 52 to 96%. It can be assumed that the antimutagenicity of the polysaccharides depends on their structural and compositional properties as well as on the different mode of action of both the mutagens tested.     

The antimutagenic properties of a polysaccharide produced by Bifidobacterium longum and its cultured milk against some heterocyclic amines

The antimutagenicity and fermentation pattern of three Bifidobacterium longum strains (B. longum, B. longum PS+, and B. longum PS-) in skim milk were studied. The increase in fermentation time significantly increased antimutagenicity with all strains tested against the mutagenicity of both 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in an Ames-like test using streptomycin-dependent strain SD510 of Salmonella typhimurium TA98. Bifidobacterium longum PS+, a polysaccharide-producing strain, had a longer lag phase but showed the highest inhibition percentage against both mutagens tested. The viability of B. longum PS+ cells was not affected by the low pH of 4.1, probably owing to the protection offered by the polysaccharide produced. The antimutagenicity of the fermented milk against Trp-P-1 was dose dependent. The strains were also able to bind with different amino acid pyrolysates, and B. longum showed the highest binding. Acetone extracts of fermented skim milk dissolved in water showed less antimutagenicity than extracts dissolved in dimethylsulfoxide. The isolated crude polysaccharide from B. longum PS+ showed a dose-dependent inhibition of the mutagenicity of Trp-P-1. Thus, we conclude that the polysaccharide of B. longum PS+ can be used as an antimutagen.     

Effects of Seasoning and Heating Device on Mutagenicity and Heterocyclic Amines in Cooked Beef

Pan-roasted beef showed a lower mutagenicity after various degrees of cooking than charcoaled one. The high mutagenicity of charcoaled beef was due to the formation of more heterocyclic amines, especially AαC (2-amino-9 H-pyrido- [2,3-b]indole) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) because of rapid and direct heating on the surface of the meat at a high temperature. Seasoning decreased mutagenicity of pan-roasted beef except the very well done sample with unchanged heterocyclic amine contents, but increased mutagenicity of charcoaled beef with decreased levels of AαC and PhIP, probably due to the change of heterocyclic amine precursors or alternatively to the occurrence of other mutagens.     

化学物质致突变性的检测方法研究进展

化学物质的致突变性评价对于预防人类疾病和控制环境污染具有非常重要的意义.为了检测化学物质的致突变性,对化学物质的致突变性评价中常用的一些主要方法及其应用的效果做了概述,并对当前致突变性检测的方法学中存在的问题以及发展趋势进行了简要的讨论.     

Antimutagenic activity against trp-P-1 of the edible Thai plant, Oroxylum indicum vent.

A methanolic extract of Oroxylum indicum strongly inhibited the mutagenicity of Trp-P-1 in an Ames test. The major antimutagenic constituent was identified as baicalein with an IC50 value of 2.78+/-0.15 microM. The potent antimutagenicity of the extract was correlated with the high content (3.95+/-0.43%, dry weight) of baicalein. Baicalein acted as a desmutagen since it inhibited the N-hydroxylation of Trp-P-2.     

Antimutagenic Acitivity against Trp-P-1 of the Edible Thai Plant,Oroxylum indicum Vent.

A methanolic extract of Oroxylum indicum strongly inhibited the mutagenicity of Trp-P-1 in an Ames test. The major antimutagenic constituent was identified as baicalein with an IC₅₀ value of 2.78±0.15 μM. The potent antimutagenicity of the extract was correlated with the high content (3.95±0.43%, dry weight) of baicalein. Baicalein acted as a desmutagen since it inhibited the N-hydroxylation of Trp-P-2.     

Assessing the Mutagenic Potential of Surface Sediments from Beijing Guanting Reservoir to Salmonella typhimurium

Mutagenicity of organic extracts from Beijing Guanting Reservoir sediments was investigated with TA98 and TA100 of Salmonella typhimurium. TA98 and TA100 were employed to detect frameshift mutation and base-pair substitution mutation, respectively. For TA100, no positive result was found, while TA98 was more sensitive and pro-mutagenic frameshift mutagens were mainly detected in sediments. Sediments from northern and southern Guanting Reservoir were at potential mutagenic risk. No mutagenicity was found in the sediments from the entrance of the tributaries, but strong mutagenicity was observed in the sediments from the outlet of the reservoir. Chemical analysis was also performed, and poor correlation was found between mutagenicity and organochlorine pesticides (OCPs). However, significant positive correlation was found for polycyclic aromatic hydrocarbons (PAHs) (r = 0.603–0.946), which showed that PAHs were dominated for the tested mutagenicity in the sediments. Polychlorinated biphenyls (PCBs) might induce mutagenicity or promote the mutagenicity of other substances.     

Mechanism of antimutagenicity of aquatic plant extracts against benzo[a]pyrene in the Salmonella assay

The mechanism of antimutagenicity of water extracts of grass-wrack pondweed (Potamogeton oxyphylus Miquel), curled pondweed (Potamogeton crispus L.) and smartweed (Polygonum hydropiper L.) towards benzo[a]pyrene mutagenicity in Salmonella typhimurium was investigated. The antimutagenic components in the aquatic plants were water-soluble, heat-resistant and had a high molecular weight; chlorophyll did not play an important role.     

Protective Effect of Nigella sativa and Nigella damascena Fixed Oils Against Aflatoxin Induced Mutagenicity in the Classical and Modified Ames Test

The antioxidant and mutagenic/antimutagenic activities of the fixed oils from Nigella sativa (NSO) and Nigella damascena (NDO) seeds, obtained by cold press-extraction from the cultivar samples, were comparatively investigated for the first time. The antimutagenicity test was carried out using classical and modified Ames tests. The fatty acid composition of the fixed oils was characterized by gas chromatography–mass spectrometry (GC-MS) while the quantification of thymoquinone in the fixed oils was determined by UPC². The main components of the NSO and NDO were found to be linoleic acid, oleic acid, and palmitic acid. The results of the Ames test confirmed the safety of NSO and NDO from the viewpoint of mutagenicity. The results of the three antioxidant test methods were correlated with each other, indicating NDO as having a superior antioxidant activity, when compared to the NSO. Both NSO and NDO exhibited a significant protective effect against the mutagenicity induced by aflatoxin B1 in Salmonella typhimurium TA98 and TA100 strains. When microsomal metabolism was terminated after metabolic activation of the mycotoxin, a significant increase in antimutagenic activity was observed, suggesting that the degradation of aflatoxin B1 epoxides by these oils may be a possible antimutagenic mechanism. It is worthy to note that this is the first study to assess the mutagenicity of NSO and NDO according to the OECD 471 guideline and to investigate antimutagenicity of NDO in comparison to NSO against aflatoxin.     

Antimutagenicity of propionic acid bacteria]

The antimutagenicity of the cell extracts of Propionibacterium shermanii VKM-103, P. pentosaceum CCM 1859 and P. acnes CCM 3322 against mutagenicity of sodium azide and N-methyl-N'-nitro-N-nitrosoguanidine was demonstrated for the first time. The extracts of propionic acid cocci didn't show such effect. The antimutagenic factor acts as a desmutagen, has polypeptide nature and evidently is an enzyme (enzymes). The inhibitory effect of the extract is due to the presence of more than one protein factor in it.     

Evaluation of mutagenic and antimutagenic activities of alpha-bisabolol in the Salmonella/microsome assay

alpha-Bisabolol (BISA) is a sesquiterpene alcohol found in the oils of chamomile (Matricaria chamomilla) and other plants. BISA has been widely used in dermatological and cosmetic formulations. This study was undertaken to investigate the mutagenicity and antimutagenicity of BISA in the Salmonella/microsome assay. Mutagenicity of BISA was evaluated with TA100, TA98, TA97a and TA1535 Salmonella typhimurium strains, without and with addition of S9 mixture. No increase in the number of his+ revertant colonies over the negative (solvent) control values was observed with any of the four tester strains. In the antimutagenicity assays, BISA was tested up to the highest nontoxic dose (i.e. 50 and 150 microg/plate, with and without S9 mix, respectively) against direct-acting (sodium azide, SA; 4-nitroquinoline-N-oxide, 4-NQNO; 2-nitrofluorene, 2-NF; and nitro-o-phenylenediamine, NPD) as well as indirect-acting (cyclophosphamide, CP; benzo[a]pyrene, B[a]P; aflatoxin B1, AFB1; 2-aminoanthracene, 2-AA; and 2-aminofluorene, 2-AF) mutagens. BISA did not alter mutagenic activity of SA and of NPD, and showed only a weak inhibitory effect on the mutagenicity induced by 4-NQNO and 2-NF. The mutagenic effects of AFB1, CP, B[a]P, 2-AA and 2-AF, on the other hand, were all markedly and dose-dependently reduced by BISA. It was also found that BISA inhibited pentoxyresorufin-o-depentylase (PROD, IC50 2.76 microM) and ethoxyresorufin-o-deethylase (EROD, 33.67 microM), which are markers for cytochromes CYP2B1 and 1A1 in rat liver microsomes. Since CYP2B1 converts AFB1 and CP into mutagenic metabolites, and CYP1A1 activates B[a]P, 2-AA and 2-AF, results suggest that BISA-induced antimutagenicity could be mediated by an inhibitory effect on the metabolic activation of these promutagens.     

Macerating Activity of endo-Polygalacturonase Produced by Saccharomyces fragilis

The effect was examined of aqueous dialyzates from 16 kinds of vegetables and fruits on the mutagenicity of some mutagens toward Salmonella typhimurium TA 100. Each dialyzate inhibited the mutagenicity of Trp-P-2, and the antimutagenicity was retained even after heating at 100°C for 20 min. Dialyzates of burdock, eggplant, spinach and apple also inhibited the mutagenicity of Trp-P-l, benzo[a]pyrene, sterigmatocystin, aflatoxin Bl, 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide and N-methyl-N′-nitroso-N-nitrosoguanidine. The dialyzates of apple reacted with S9 mix and Trp-P-2. A Sepharose CL 6B gel filtration study of the dialyzates of apple indicated that the antimutagenic activity of these dialyzates on Trp-P-2 and AF-2 was mainly detectable in the polyphenol-rich fractions.     

Cytochrome P4501A1-inhibitory action of antimutagenic anthraquinones in medicinal plants and the structure-activity relationship

We have earlier found that flavones and flavonols in vegetables specifically inhibited one of the carcinogenesis-related enzymes, cytochrome P450 (CYP) 1A1, and subsequently suppressed the mutagenicity of food-derived carcinogens. In this study, we explored other candidates for the enzyme inhibitor in Chinese medicinal plants. Some of them were antimutagenic toward 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). For example, Rheum officinale contained large amounts of anthraquinones as the active compounds, 3.4 mg of emodin, 2.1 mg of chrysophanol and 1.8 mg of rhein in 10 g of dry matter. Anthraquinones showed similar IC50 values for antimutagenicity against Trp-P-2 to those for inhibition of the N-hydroxylation activity of CYP1A1 toward Trp-P-2, indicating that the antimutagenicity was attributable to CYP inhibition. The structure-activity relationships were then examined with 14 commercial chemicals, and it was found that the interaction with an enzyme required three rings and an oxygen group in the side ring. This characteristic is similar to that of flavones and flavonols.     

Mutagenicity and antimutagenicity of air-borne particulates

A methanol extract of air-borne particulates collected in a suburban area of Okayama City showed not only mutagenicity but also antimutagenicity in the Ames test. Thus, when the mutagenicity of this preparation in Salmonella typhimurium TA98 (with metabolic activation) was measured, we observed that the dose response reached a plateau at 27 m3 air equivalent of the particulate, showing approximately equal numbers of revertants in the dose range 27-270 m3 equivalent. This plateau formation was not seen in the dose response of a blue-cotton extract of this preparation: the extract gave a linearly increasing dose response up to 270 m3 equivalent. This finding suggests that some factors that inhibit the mutagenicity were present in this methanol extract and that these inhibitors were not adsorbable to blue cotton, an adsorbent selective for compounds having 3 or more fused rings. From the portion unadsorbed to blue cotton, we isolated the antimutagenic factors and identified them as long-chain fatty acids: palmitic, stearic, oleic and linoleic acids. Analysis of several samples, including those from other parts of Japan, has suggested that these antimutagenic fatty acids are ubiquitous in air-borne particulates.     

噻吩磺隆的毒性及致突变性

选用大鼠、豚鼠及家兔,采用经口及皮肤,粘膜染毒途径,研究其急性毒性。同时有Ames试验,小鼠骨髓嗜多染红细胞微核试验及小鼠睾丸初级精母细胞染色体畸变试验进行致突变性研究,了解噻吩磺隆的毒性及致突变性。大鼠急性经口LD50大于5000mg／kg,经皮LD50大于2000mg／kg。家兔皮肤刺激试验阴性,轻度眼刺激性和弱致敏性。Ames试验,微核试验及小鼠睾丸初级精母细胞染色体畸变试验结果均为阴性。结论 噻吩磺隆属低毒性农药,在本实验条件下无致突变作用。