Mutagens in coffee and tea

Tea consumption and cancer

Following the report from Hawaii (Heilbrun et al., 1986) of relationships between tea consumption and respectively rectal cancer (positive) and prostate cancer (negative), these questions were examined using data from a prospective mortality study of London men initiated in 1967. The small numbers of men who did not usually drink any tea prevented a reliable study of this sub group. Nevertheless no evidence of a dose-response relationship was found for rectal, colon or prostate cancer. Significant relationships were found, however, between tea consumption and deaths from stomach, lung and kidney cancers. In the case of stomach and lung cancer, these were partly due to the effects of social class and smoking, and possible reasons are considered for the residual relations.

Genetic toxicology evaluation of commercial beers. I. Development of procedures for the preparation of extracts from commercial beer products

Commercial beer was subjected to an investigation in order to establish standard conditions for preparing organic solvent extracts to be used in short-term genetic screening assays. Test samples for use in the evaluation were prepared by mixing several brands of commercially available beer into a composite pool which was then spiked with the mutagen, 2-nitrofluorene. The composite sample was then concentrated using varying ratios of beer to XAD-2 resin in a 1.5 cm X 30 cm column. Dry-weight analyses indicated that significant amounts of residue could be trapped by XAD-2 resin. Columns were sequentially eluted by methylene chloride, acetone and methanol followed by evaporation of the solvents under nitrogen gas. Residues from commercial products were not mutagenic, but mutagenic activity could be detected in residues from spiked beer, yielding nearly 90% of the expected biological activity in S. typhimurium TA98. A standard method amenable to processing large volumes of beer products was devised for application to other projects.

Studies on the use of plant extracts in assessing the effects of plant metabolism on the mutagenicity and toxicity of pesticides

We have carried out studies on the effects of plant metabolism on the mutagenicity of agricultural chemicals. Our approach is to use a cell-free plant extract, as a source of metabolic enzymes, in a standard Ames test. Using a number of test compounds, we observe that plant metabolism can alter the mutagenicity of several pesticides, and can in some instances give rise to metabolites apparently unique from those which are formed in animal cells. A number of parameters of the assay have been examined, and we find that the assay temperature and preincubation of the pesticide with the extract can significantly alter the outcome of the test. We also have devised a method of controlling for the effects that natural extracts can have on the spontaneous reversion rate of the Salmonella tester strains, in an effort to distinguish slight mutagenic responses from the effects of nutrients (e.g. histidine for his- bacteria) in the assay.

Increased sister chromatid exchange associated with smoking and coffee consumption

Sister chromatid exchange (SCE) is a very sensitive cytogenetic assay for detecting exposure to chemical mutagens and carcinogens. One application of SCE is the monitoring of populations believed to be exposed to such agents. We have, however, relatively little knowledge about common lifestyle factors that may influence SCE and therefore complicate any study designed to examine the effects of exposure to genotoxins. In this study, we assessed the effect of cigarette smoking and coffee consumption on SCE. Smoking was associated with an increase of approximately 2 SCEs per cell and a decrease in cell proliferation. A positive linear relationship between SCE and coffee consumption was also observed. This effect was similar for smokers and nonsmokers. Additionally, the folic acid content of cell culture medium seemed to affect neither SCE nor cell proliferation.

Mutagenicity of instant coffee and its interaction with dimethylnitrosamine in the micronucleus test

The mutagenicity of instant coffee and its interaction with dimethylnitrosamine (DMN) were examined in mice using the micronucleus test. Although neither a single nor multiple administration of instant coffee by gavage induced a significant rise in micronucleated cells over the dose range tested (100-2500 mg/kg), there was a tendency for the number of micronucleated cells to increase in a dose-related fashion. When coffee was administered with DMN, the difference in the frequency of micronucleated cells was small in comparison to a single treatment with DMN alone, thus indicating a lack of synergism between coffee and DMN.

Implication of active oxygen species in the direct-acting mutagenicity of tea

The present study shows that the L-arabinose resistance test with Salmonella typhimurium detects that freshly infused tea is highly mutagenic in the absence of mammalian microsomal activation. Both the mutagenesis protocol (preincubation test) and the additional genetic characteristics of the bacterial tester strain (excision repair deficiency, normal lipopolysaccharide barrier and the presence of plasmid pKM101) were critical factors in the optimal induction by tea of forward mutations to L-arabinose resistance. The TA104 strain--a histidine auxotroph specific to oxidative mutagens--was the most sensitive tester strain of the Ames test to the direct-acting mutagenicity of tea. In comparison with strain TA104, the sensitivity of the Ara forward mutation test was 18 times higher, one cup of tea (200 ml) inducing 3 X 10(6) AraR mutants. More than 90% of the mutagenicity of 150 microliter of a fresh tea infusion, or that of the equivalent amount (1.32 mg) of the corresponding lyophilized residue, was suppressed by 10 units of catalase. In contrast to catalase, superoxide dismutase was rather ineffective. These results indicate that hydrogen peroxide is produced in tea solutions, playing an essential role in its mutagenicity. In comparison, the role of superoxide anion seems negligible. Like catalase, the chelating agent DETAPAC showed a protective effect with respect to the mutagenicity of tea, suggesting the additional implication of hydroxyl radicals.

Simple and sensitive determination of methylglyoxal in biological samples by gas chromatography with electron-capture detection

Methylglyoxal was allowed to react with 4,5-dichloro-1,2-phenylenediamine, and the 6,7-dichloro-2-methylquinoxaline formed was determined by gas chromatography with electron-capture detection. The standard curve of the quinoxaline was linear up to 160 pmol/ml. The recoveries of methylglyoxal from coffee and rat liver homogenate were 84.1 and 77.6%, respectively. This procedure was very selective and so sensitive that as little as 9 fmol of the quinoxaline could be measured in biological and food samples.

Biological and chemical studies on overheated brewed coffee

Vapour formed from overheated decaffeinated coffee was condensed and tested for mutagenicity using the Ames assay in Salmonella typhimurium strains TA98 and TA100. Vapour produced at 73 and 100 degrees C exhibited no mutagenicity. The basic fraction of vapour produced at 350 degrees C showed weak mutagenicity towards strains TA98 with metabolic activation. The chemical analysis of this fraction identified pyridines and pyrazines as the major constituents. None of the compounds identified in this fraction has been reported as mutagenic when tested in the Ames assay.

Mutagenicity of human urine after the consumption of fried salted salmon

Mutagenicity in the urine of four non-smoking individuals who had eaten salted salmon cooked at home for both lunch and supper was monitored by means of Salmonella/microsome mutagenicity tests. Extracts from fresh and salted salmon had the same level of mutagenicity after being cooked for 10 min at 200 degrees C, but no activity was detected before cooking. Salmonella strains TA98 and TA1538 were equally sensitive to the mutagens and required metabolic activation. No mutagenicity was shown with TA100 and TA1535. Urine samples were tested using a concentrate prepared by means of an XAD-2 resin column. Mutagenicity was detected mainly in urine excreted during 4-5 hr after the ingestion of cooked salmon, but only weak mutagenicity, or none at all, was detected in the urine after the ingestion of vegetables. The levels of urinary mutagenicity due to salmon consumption were not affected when cabbage was eaten simultaneously. The excretion of mutagenic substances was completed within about 20 hr, and there were almost no mutagens in the urine 24 hr after the ingestion of cooked salmon.

Coffee is highly mutagenic in the L-arabinose resistance test in Salmonella typhimurium

The present study shows that the L-arabinose resistance test in Salmonella typhimurium detects coffee as a strong mutagen in the absence of mammalian microsomal activation. The response of the Ara forward mutation assay was 8.5 times higher than that of TA104, which is the most sensitive to coffee of the tester strains of the Ames test. Both the mutagenesis protocol (preincubation test) and the additional genetic characteristics of the bacterial tester strain (excision repair deficiency, normal lipopolysaccharide barrier, and the presence of plasmid pKM101) were critical factors in the optimal induction by coffee of forward mutations to L-arabinose resistance. All ten samples of roasted coffee analyzed with the Ara assay were highly mutagenic: one cup of coffee (150 ml) was calculated to induce 3-4 X 10(6) AraR mutants. In contrast, coffee prepared from unroasted beans (green coffee) had no mutagenic activity. Regular- and sugar-roasted coffees showed similar mutagenicities, but the specific mutagenic activity of instant coffees (1559 AraR mutants/mg) was almost 2 times that of noninstant ones (834 AraR mutants/mg). The Ara assay allowed the direct testing of coffee, although it was demonstrated that lyophilization has no effect on the mutagenicity of this beverage. Like roasted coffee, roasted barley induced a large number of AraR mutants per mg (227), though its specific mutagenic activity was approximately 4 and 7 times lower than that of noninstant and instant coffees, respectively.

Mutagenicity of urine from young male smokers and nonsmokers

The mutagenicity of urine from a healthy population of young adult men (average age of 23 years), including 61 smokers and 107 nonsmokers, was investigated with the Salmonella/microsome test using the tester strain S. typhimurium TA98. In quantifying the assay, the use of dichloromethane was suitable for eluting the mutagenicity of smokers' urine from the XAD-2 resin column. We assayed mutagenicity in condensates of such dichloromethane eluates and found that the mutagenicity of smokers' urine was significantly higher than that of nonsmokers' urine. In the smokers' group, correlation coefficient between "the mutagenicity of the urine" and "the actual number of cigarettes smoked on the day of urine collection" or "the average number of cigarettes smoked per day" was statistically significant at 0.266 or 0.454, respectively. Our results suggest a correlation between the increase of mutagens in urine and smoking habits.

Suppressive effects of coffee on the SOS responses induced by UV and chemical mutagens

SOS-inducing activity of UV or chemical mutagens (AF-2, 4NQO and MNNG) was strongly suppressed by instant coffee in Salmonella typhimurium TA1535/pSK1002. As decaffeinated instant coffee showed a similarly strong suppressive effect, it would seem that caffeine, a known inhibitor of SOS responses, is not responsible for the effect observed. The suppression was also shown by freshly brewed coffee extracts. However, the suppression was absent in green coffee-bean extracts. These results suggest that coffee contains some substance(s) which, apart from caffeine, suppresses SOS-inducing activity of UV or chemical mutagens and that the suppressive substance(s) are produced by roasting coffee beans.

Black tea consumption and cancer risk: a prospective study

In a prospective cohort study, men of Japanese ancestry were clinically examined from 1965 to 1968. For 7,833 of these men, data on black tea consumption habits were recorded. Since 1965, newly diagnosed cancer incidence cases have been identified: 152 colon, 151 lung, 149 prostate, 136 stomach, 76 rectum, 57 bladder, 30 pancreas, 25 liver, 12 kidney and 163 at other (miscellaneous) sites. Compared to almost-never drinkers, men habitually drinking black tea more than once/day had an increased relative risk (RR) for rectal cancer (RR = 4.2). This positive association (P = 0.0007) could not be accounted for by age or alcohol intake. We also observed a weaker but significant negative association of black tea intake and prostate cancer incidence (P = 0.020). There were no significant associations between black tea consumption and cancer at any other site.

Investigation of coffee in Drosophila genotoxicity tests

Two preparations of coffee (instant coffee and freeze-dried home-brew coffee) were tested in different mutagenicity assays in germ cells as well as in somatic cells of Drosophila melanogaster. The three end-points assayed in germ cells were sex-linked recessive lethals (mainly gene mutations and small chromosome aberrations), dominant lethals (cytotoxic effects as well as genotoxic effects) and sex-chromosome losses (chromosome breakage and non-disjunction). The aqueous coffee solutions were fed either to adult male flies for 3 days or to growing larvae during the whole larval development. Treated males were crossed with appropriately marked females, and the different genetic end-points were analysed in the F1 or F2 generation. The test concentrations (instant coffee 4% (w/v), home-brew coffee 3%) were acutely toxic in adult males (killing approximately 75 and 90% of the exposed flies, respectively). No increase in deaths was caused in larvae by the same concentrations. Only cytotoxic effects were observed in the test for dominant lethals. No conclusive genotoxic effects could be detected in any of the three germ cell assays. The coffee preparations were also tested for induction of mutation and mitotic recombination in somatic cells of the wing imaginal disc. Larvae trans-heterozygous for two recessive wing hair markers were fed high concentrations of the coffees for varying periods of time. Wings of surviving adult flies were analysed for mosaic spots. Twin spots exhibiting both mutant phenotypes are produced by mitotic recombination; single spots showing one or the other phenotype are the result of somatic mutation, such as gene mutation or deletion, or of mitotic recombination. Both coffees had weak effects on normal (repair-proficient) cells as well as on excision repair-defective cells in this assay. Additional experiments with pure caffeine and decaffeinated coffee show that these weak effects in somatic cells were most probably caused by the caffeine present in the two coffees.

The Copenhagen case-control study of bladder cancer. II. Effect of coffee and other beverages

During the years 1979-1981 a population-based case-control study of bladder cancer including papilloma was performed in greater Copenhagen. A total of 371 patients (280 males; 91 females), and a comparable age- and sex-stratified group of 771 controls (577 males; 194 females) remained for logistic regression analysis. Controls were selected at random from the general population of the study area. All persons were questioned about their drinking habits with respect to coffee, tea and other beverages, as well as their exposure to a number of known or suspected risk factors for bladder cancer. After adjustment for tobacco smoking, the relative risk of bladder cancer in relation to coffee drinking was not statistically significant among either men or women. A significant association was found between bladder cancer and tea drinking among men, but with no regular trend for increasing consumption. An association was found between risk of bladder cancer and both total daily liquid intake and non-cola soft drinks. This population-based case-control study provides no evidence of an isolated influence of coffee drinking or caffeine intake on bladder cancer risk.

Genotoxicity of cocoa in a series of short-term assays

Cocoa powder was evaluated for genotoxic activity and found to be inactive in the Ames assay, the mouse lymphoma assay, cytogenetic assays measuring chromosome breakage and SCE, and a cell transformation assay using Balb/c-3T3 cells. Although pure theobromine has been shown to be active in some of these test procedures, the levels of this methylxanthine present in cocoa powder were insufficient to elicit responses in this battery of tests.

Implication of hydrogen peroxide in the mutagenicity of coffee

A cup of instant coffee (150 ml) of normal strength (15 mg/ml) was found to contain about 500 and 750 micrograms of hydrogen peroxide soon after its preparation at 37 degrees C and 80 degrees C, respectively, but the concentration of hydrogen peroxide in the coffee increased with time for up to 24 h after its preparation. Thus coffee contains a hydrogen peroxide generating system. As extracts of green coffee beans were found to have very low capacity to generate hydrogen peroxide, this generating system is produced by roasting coffee beans. Hydrogen peroxide itself was only weakly mutagenic to Salmonella typhimurium TA100, but in the presence of methylglyoxal, which is also present as a mutagenic component in coffee, hydrogen peroxide showed strong mutagenicity. Hydrogen peroxide and methylglyoxal seem to be responsible for most of the mutagenicity of instant coffee.

Instant and brewed coffees in the in vitro human lymphocyte mutagenicity test

Incubation of instant and 'home brew' coffees (caffeinated and decaffeinated) and of coffee aroma with cultured human lymphocytes in the presence and absence of S-9 increased the number of total aberrations. However, the increase was smaller in the presence of S-9 than in its absence. Pure caffeine tested with or without S-9 at doses equivalent to levels in caffeine-containing coffee did not give statistically significant increases of any type of aberration when compared with controls. In all in vitro test systems used to date, coffee and coffee aroma or their reactive compounds were metabolically deactivated in the presence of S-9. This could explain the negative results obtained in mutagenicity assays in vivo.

Clastogenic agents in the urine of coffee drinkers and cigarette smokers

Organic material from the urine of smokers, coffee drinkers, and controls was extracted and separated into 3 fractions of differing hydrophobicity using preparative reversed-phase high-pressure liquid chromatography. Fractions were assayed for clastogenic activity using Chinese hamster ovary cells. Smoking, coffee drinking, or both habits together resulted in a substantial increase in the genotoxicity of organic material in all 3 fractions. The clastogenicity of fractions 1 and 2 (the two most hydrophilic) was abolished by the addition of either catalase or superoxide dismutase to the Chinese hamster ovary cell system, suggesting the involvement of active oxygen species in the clastogenic response. Clastogenicity of fraction 3, however, was resistant to the action of catalase and superoxide dismutase. Fractions were tested for their ability to generate hydrogen peroxide in vitro during a 10-min incubation at elevated pH. Fractions 2 and 3, but not fraction 1 from smokers, coffee drinkers, or those with both habits generated significantly more hydrogen peroxide at high pH than did the corresponding fractions from control subjects. For fractions 2 and 3 but not 1, the ability of a sample to generate hydrogen peroxide at high pH was positively correlated with its ability to generate chromosome aberrations at neutral pH in tissue culture. The data indicate that both coffee drinking and cigarette smoking result in the appearance of clastogenic materials in urine, and suggest that such clastogenic agents may produce chromosome aberrations via the production of active oxygen species.

The influence of roasting procedure on the formation of mutagenic compounds in coffee

Mutagenic products can be formed during the processing of food and especially as a result of heat treatment. Direct acting mutagenic activity was found in extracts of instant coffee and roasted coffee beans using Salmonella typhimurium TA100 in vitro. The mutagenic activities of the four pure coffee varieties examined (Coffea arabica Santos, Coffea arabica Columbia, Coffee robusta Indonesia, Coffee robusta Camerun) were within the same range. Twenty milligrams per plate freeze-dried powder prepared from aqueous roast coffee extracts induced between six and ten times the number of revertants found in the negative controls. Green coffee beans had no mutagenic activity. Mutagenicity increased with roasting time up to 4 min in the Probat drum roaster and then remained constant (i.e. no further increase after 8 min, the time normally used to roast coffee). The genotoxic compounds were quickly formed at temperatures below 220 degrees C (in normally roasted coffee the beans must reach a temperature of 220 degrees C). Mutagenic activity was independent of the roasting procedure (Jetzon procedure v. Probat drum roaster).

Characteristics of major mutagenicity of instant coffee

Detailed quantitative studies on the mutagenicity of methylglyoxal showed that its contribution to the total mutagenicity of instant coffee on S. typhimurium TA100 was minor although we reported previously (Kasai et al., 1982) that its contribution to the mutagenicity of freshly brewed coffee was about 50%. Cysteine suppressed the mutagenicity of methylglyoxal and of methylglyoxal when added to instant coffee, but did not affect the mutagenicity of coffee itself. Catalase suppressed most of the mutagenicity of coffee, but not that of methylglyoxal or of methylglyoxal added to coffee.

Mutagenicity studies on coffee. The influence of different factors on the mutagenic activity in the Salmonella/mammalian microsome assay

Recently, mutagenic activity on several strains of Salmonella typhimurium has been found in many heat-processed foodstuffs. The previously reported direct-acting mutagenic activity of coffee in Salmonella typhimurium TA100 (Ames assay) was confirmed in our study. In addition to TA100, a mutagenic effect of coffee was also found by using the newly developed strain TA102. The mutagenic activity was abolished by the addition of rat-liver homogenate. 10% S9 mix completely eliminated the mutagenic activity of 30 mg of coffee per plate. The addition of reduced glutathione to active S9 further decreased the mutagenic activity and also reduced the mutagenicity together with inactivated S9. The compound or compounds responsible for this inactivation are heat-labile and seem to be located in the cytosol fraction of the S9. Part of the mutagenicity of coffee was also lost spontaneously upon incubation at temperatures between 0 degrees and 50 degrees C. The loss of activity was dependent on temperature, being more pronounced at 50 degrees C compared to 0 degrees C (at 50 degrees C approximately 50% of the mutagenic activity was lost after 6 h). As anaerobic conditions prevented this loss of mutagenicity almost totally, oxidative processes are probably responsible for the inactivation. The stability of the mutagen was not influenced by incubation at low pH values (pH 1-3), with or without the addition of pepsinogen. The mutagenic properties of methylglyoxal, which to some extent could be responsible for the mutagenic activity of coffee, were compared with those of coffee. Methylglyoxal was strongly mutagenic towards Salmonella typhimurium TA100 and TA102. Its mutagenic activity was partially inactivated by the addition of 10% S9. Glyoxalase I and II together with reduced glutathione abolished the mutagenic activity of methylglyoxal but reduced the mutagenicity of coffee by only 80%. Since these enzymes occur in mammalian cells, the mutagenic compound(s) of coffee could also be degraded in vivo. This conclusion is supported by the fact that a long-term carcinogenicity study with rats was negative. These results clearly demonstrate that the effects observed in vitro do not necessarily also occur in vivo, but that in vitro experiments may contribute to the understanding of fundamental mechanisms of chemical carcinogenesis.

Mutagen content of wines contaminated with common yeasts

Wines exhibiting a microbial haze were collected and their microbial contents identified. Contaminant yeast species were cultured in grape musts under controlled conditions and extracts of the resultant wines were assayed for mutagen content using four strains of Salmonella in the Ames Salmonella/microsome/faecalase system. The wine extracts exhibited some toxicity to Salmonella but no mutagen content. It would appear that mutagen content is more a function of the grape species and must preparation than of microbial metabolism during fermentation.

Diet and other risk factors for cancer of the pancreas

The findings of a case - control study of cancer of the pancreas, which was conducted in the Baltimore metropolitan area, are reported. Two hundred one patients with pancreatic cancer were matched on age (+/- 5 years), race, and sex to hospital and non-hospital controls, the latter selected by random-digit-dialing (RDD). All subjects were interviewed regarding diet, beverage consumption, occupational and environmental exposures, and medical and surgical history. Significantly decreased risks were associated with consumption of raw fruits and vegetables and diet soda, and significantly increased risks were associated with consumption of white bread when cases were compared with hospital and RDD controls. A significantly reduced risk was associated with consumption of wine when cases were compared to RDD controls. Risk ratios for consumption of coffee were not significantly different from one, although there appeared to be a dose - response relationship in women. A moderate but statistically nonsignificant increase in relative odds was found for cigarette smoking, and cessation of smoking was associated with a marked reduction in risk. No significant associations were found with particular occupational exposures. Tonsillectomy was associated with a significantly reduced risk, a finding that has been observed for other cancers as well. The current evidence indicates that pancreatic cancer is likely to result from a complex interaction of factors and suggests that the study of its etiology requires a multidisciplinary approach involving both laboratory and epidemiologic components.

Ames mutagenicity tests of overheated brewed coffee

Five kinds of coffee samples were prepared from a commercial drip-grind coffee in order to examine the mutagenicity of brewed coffee using the Ames test. The samples prepared were a thick coffee syrup, coffee solid residues, dichloromethane and ethanol extracts of solid residues, a dichloromethane extract of a distillate from normally heated brewed coffee and dichloromethane extracts of distillates from overheated (150-300 degrees C) brewed coffee. The samples were tested for mutagenicity towards Salmonella typhimurium strains TA98 and TA100 both with and without metabolic activation (S-9 mix). Only the extracts of the distillates obtained from coffee heated to 150 degrees or 300 degrees C exhibited mutagenicity towards strain TA98 with S-9 mix.

Investigation of coffee in sister chromatid exchange and micronucleus tests in vivo

Administration of a single oral dose of instant coffee to Chinese hamsters at levels up to 2.5 g/kg body weight did not increase the frequency of sister chromatid exchanges. Furthermore, five consecutive daily oral doses of instant coffee given to Swiss OF-1 mice up to 3 g/kg/day did not induce increases in micronuclei above spontaneous levels. Similarly, no effect was observed in the micronucleus test after mice received two oral doses of coffee aroma of up to 50 ml/kg.

Mutagenicity of instant coffee on cultured Chinese hamster lung cells

Coffee showed mutagenic activity in cultured Chinese hamster lung (CHL) cells as assessed by using diphtheria toxin resistance as a selective marker. Most of the mutagenicity was suppressed in the presence of sodium bisulfite. The contribution of methylglyoxal to the total mutagenicity of coffee was less than 3%.

Time-course of mutagenicity due to flavonols in a pickled vegetable

The mutagenicity of the leafy vegetable, Takana (Brassica juncia var. integrifolia), pickled with salt for various durations was examined. The mutagenicity increased with increasing duration of pickling time, and analysis by HPLC showed that is was caused by mutagenic flavonols. The flavonols contained in the fresh Takana as glycosides were found to be freed by pickling. This was confirmed by acid hydrolysis.

Roasting coffee beans produces compounds that induce prophage lambda in E. coli and are mutagenic in E. coli and S. typhimurium

Freshly brewed blended coffee, instant coffee and instant caffeine-free coffee induced prophage lambda in lysogenic E. coli K12, strain GY5027. Because coffee prepared from green beans by the same extraction method as used for freshly brewed blended coffee had no prophage-inducing activity, this activity may be attributed to compounds produced in the roasting process. Roasting also produced compounds that were mutagenic in S. typhimurium TA100 and E. coli WP2 uvrA/pKM101.

Isolation of streptomycin-dependent strains from salmonella typhimurium TA98 and TA100 and their use in mutagenicity tests

Streptomycin-dependent (SMd) mutant strains of Salmonella typhimurium TA98 and TA100 were isolated. A highly sensitive detection system was obtained by using these SMd derivatives for the SMd leads to SMind mutation. The system was available for testing the mutagenicities of samples containing histidine, such as food.

Inhibitory effects of phenolics, teas and saliva on the formation of mutagenic nitrosation products of salted fish

The objectives of this study were to simulate in vitro some of the conditions that may prevail in man during the ingestion of a meal and to quantitate the inhibitory effect of phenolics and phenolic-containing beverages on the formation of mutagenic nitrosation products. The test system consisted of nitrosating (pH 2, 1 h, 37 degrees C) an aqueous fraction of a salt-preserved Chinese fish (Pak Wik) with or without the inhibitors to be tested and estimating the frequency of his+ revertants per survivor of Salmonella typhimurium (strain TA1535). The phenolics and teas were added to the nitrosation mixture. Catechin, chlorogenic acid, gallic acid, pyrogallol and tannic acid suppressed the formation of mutagenic nitrosation products. The inhibitory efficiency was comparable to that of ascorbic acid. A Japanese, a Chinese and a Ceylonese tea also prevented the formation of mutagenic nitrosated fish products at doses which are usually consumed by man. Moreover, saliva exerted an inhibitory effect. The inhibitory effect was not additive when the phenolics or saliva were added concurrently to the nitrosation mixture. The possibility that phenolics are involved in the apparent chemopreventive effect of fruits and vegetables is discussed.

Sulfite suppresses the mutagenic property of coffee

The mutagenicity of instant and freshly brewed coffee on Salmonella typhimurium TA100 and TA98 without S9 mix was inactivated by sodium sulfite. Sulfite ion at a dose of 200 ppm almost completely inactivated the mutagenicity of coffee made in the ordinary way (5-15 mg dry weight/ml). Sodium bisulfite and potassium metabisulfite had similar effects. On the contrary, L-ascorbic acid enhanced the mutagenicity of coffee. Sodium sulfite also inactivated the phage-inducing activity of coffee in inductest III. Sodium sulfite completely suppressed the mutagenicities of 1,2-dicarbonyls, namely diacetyl and glyoxal. Diacetyl is present in coffee, beer, butter and other foods and drinks. Because sodium sulfite, sodium bisulfite and potassium metabisulfite are widely used as food additives, they should be useful in reducing the levels of mutagens in foods.

Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea

Several plant phenolics, one instant coffee, one instant decaffeinated coffee, one roasted coffee, one Japanese tea, one black Indian tea, and one Chinese tea were examined for their inhibitory properties on mutagenicity resulting from the nitrosation of methylurea. Mutagenicity was estimated as the number of his+ revertants per survivor of Salmonella typhimurium TA1535 which was exposed in suspension to the nitrosation mixtures and the modulating agents for 20 min. Tannic acid, gallic acid and chlorogenic acid suppressed the mutagenicity of the model nitrosation system at concentrations similar to or even lower than ascorbic acid. The three tested coffees and three tested teas exerted an inhibitory effect on the mutagenicity of the test system at doses at which they are consumed.

Mutagenicity of hydrolysates of citrus fruit juices

Hydrolysates of citrus fruit juice were mutagenic according to the Ames test. The citrus fruit juices were hydrolysed with 1 M HCl, hesperidinase, naringinase and human intestinal bacteria. The hydrolysates were successively extracted with n-hexane, chloroform, diethyl ether and ethyl acetate. The mutagenicities of extracts were assayed by the Ames test, and the mutagens were analysed by gas chromatography and mass spectrometry (GC-MS). Mutagenicities of hydrolysates of citrus fruit juice were found in both the chloroform extracts and the ether extracts. The chloroform extracts were mutagenic to TA98 and TA100 with S9 mix, and the ether extracts were mutagenic to TA98 and TA100 with or without S9 mix. Some known flavonols such as kaempferol and quercetin were detected in the extracts of the hydrolysates by GC-MS. It is suggested that the mutagenicity of the extracts originated from those flavonols in the citrus fruit juice.

Induction of mitotic gene conversion by browning reaction products and its modulation by naturally occurring agents

Mitotic gene conversion in the D7 strain of Saccharomyces cerevisiae was significantly enhanced by exposure to non-enzymatic browning reaction products. These products were formed during the heating of sugar (caramelization reaction) or sugar-amino acid mixtures (Maillard reaction) at temperatures normally used during the cooking of food. Several modulating factors of this convertogenic activity were identified. These factors included two main groups: (1) trace metals which are widely distributed in the environment; and (2) several cellular enzymatic systems. The convertogenic activities of a heated glucose-lysine mixture and a commercial caramel powder were completely suppresses when yeast were concurrently exposed to these products and to either FeIII or CuII. Equimolar concentrations of MnII or sodium selenite had no effect on the convertogenic activity of the products of either model system. Horse-radish peroxidase, beef liver catalase and rat liver S9 preparations each decreased the frequency of gene conversion induced by the caramel powder and the heated glucose-lysine products. This modulating activity of the enzymes was lost if they were heat-inactivated. These studies indicate the presence of a variety of protective mechanisms which can modify genotoxic components in complex food mixtures.

Nonmutagenicity in vivo of the food flavonol quercetin

Mice given quercetin per os at concentrations that were about 10(3) times greater than the estimated average human intake of total flavonols were tested for mutagenicity with 2 complementary in vivo mutagenicity/carcinogenicity screening tests--the micronucleus test and the host-mediated assay employing the Ames Salmonella tester strain TA 98 as indicator organism. No mutagenic effect was detected with either test.

Mutagenicity screening of foods I. Results with beverages

Following a number of recent reports on the presence of mutagens in certain foods, a general survey of the mutagenic potential of a wide variety of food products has been initiated. Here, results for samples of 28 widely consumed beverages from 13 general categories are reported. Each sample was concentrated and fractionated by polarity and solubility to give up to seven fractions, each of which was assayed for mutagenic potential with Salmonella typhimurium TA98 and TA100 +/- fortified liver homogenate. Fractions showing evidence of either mutagenicity or toxicity were retested at the same and lower concentrations. The utility of the fractionation procedure and the sensitivity of the screening strategy were established by assaying six beverages spiked with known mutagens prior to fractionation. Statistical analysis of the data resulted in positive findings for seven beverages, although confirmation of these results through analysis of a second sample was obtained only for red wine, grape juice, and instant coffee. The remaining 21 beverages showed no strong evidence of mutagenic activity. For those foods for which the variation among replicate plates was largest, the false-positive rate for the two-stage screening procedure employed was estimated to be less than 1% while the false-negative rate for a beverage inducing a threefold increase in the background mutation rate was conservatively estimated to be limited to 14%.