Mutagens in coffee and tea

Clastogenicity of furans found in food

Cultured Chinese hamster ovary (CHO) cells were exposed for 3 h to furan and 6 furan derivatives (furfural, furfuryl alcohol, 5-methyl furfural, 2-methyl furan, 2,5-dimethyl furan and 2-furyl methyl ketone). Each of the 6 furan derivatives induced a relatively high frequency of chromatid breaks and chromatid exchanges in the absence of a liver microsomal activation preparation. The response of the furans to the addition of an S9 mixture differed. The clastogenic activities of 5-methyl furfural, 2-furyl methyl ketone, furfural and furfuryl alcohol were increased, whereas that of 2-methyl furan and 2,5-dimethyl furan were significantly decreased. Furan itself showed a clastogenic activity only in the presence of an S9 mixture.

Non-mutagenicity of urine from coffee drinkers compared with that from cigarette smokers

The urine of human coffee drinkers who ingested 12 g of instant coffee per day, during 4 days in a first experiment or 12 g within 2 h in a second experiment, was fractionated by XAD-2 column chromatography. The non-polar urine fractions so obtained were not mutagenic in the Ames Salmonella tester strains TA98 or TA100 in either experiment, either with or without beta-glucuronidase treatment of the urine. The non-polar urine fraction of smokers, who smoked 20--30 cigarettes per day during 4 days in the first experiment or 7--18 cigarettes during 7 h in the second experiment, was mutagenic when metabolically activated.

Effect of pH and ammonium ions on mutagenic activity in cooked beef

Controversy surrounding the extraction procedure commonly used for isolating and concentrating mutagens from foods has resulted in a need for the re-examination of the reported mutagenicity in fried hamburgers. Using a procedure in which Na2SO4 and NaOH are substituted for (NH4)2SO4 and NH4OH respectively, mutagenic activity in extracts of hamburgers fried for 5 min appeared to be unchanged. However, when organic extractions are performed at pH conditions more moderate than those generally employed to isolate mutagens from foods, a 30-50% decrease in mutagenicity is observed.

Mutagenicity of hydrolysates of tea infusions

Hydrolysates of infusions of green tea and black tea were mutagenic by the Ames test. The tea infusions were prepared by a regular method and were hydrolysed with 1 M HCl, hesperidinase, naringinase and human intestinal bacteria. The hydrolysates were successively extracted with chloroform, diethyl ether and ethyl acetate. The mutagenicities of the extracts were assayed by the Ames test, and the mutagens were analysed by GC-MS. The ether extracts of the hydrolysates of infusions of both green tea and black tea were mutagenic of TA98 and TA100 with or without S9 mix. The most common mutagenic flavonols, kaempferol, quercetin and myricetin, were detected in the extract by GC-MS, and their combined mutagenicity represented about 70% of the whole mutagenic activity in the extract.

Clastogenic activity of caramel and caramelized sugars

Cultured Chinese hamster ovary (CHO) cells were exposed for 3 h to caramelized solutions of the sugars sucrose, glucose, mannose, arabinose, maltose and fructose. Each of these caramelized sugars induced a relatively high frequency of chromosome breaks and exchanges in the treated cells. The non-caramelized sugars did not increase the frequency of chromosome aberrations. A potent clastogenic effect was also observed when a commercially used caramel powder was assayed. Up to 54% of all examined metaphase plates of the treated CHO cells had at least one chromosome break or exchange. This chromosome-damaging action of commercial caramel powder was reduced in the presence of liver microsomal (S9) preparation or FeII and FeIII. The transition metals CuII and MnII neither enhanced nor reduced the clastogenic activity of the caramel powder.

Mutagenicity of alcoholic beverages

The mutagenicities of evaporated residues of alcoholic beverages were tested by the Ames method with the modification of pre-incubation, by using Salmonella typhimurium TA100 and TA98. 12 of 13 brands of whisky were mutagenic to TA100 without S9 mix. Addition of S9 mix decreased or abolished these mutagenicities. 5 brands of brandy and 1 apple brandy were tested, and all showed a similar type of mutagenicity to that of whisky. A fraction of brand-K whisky, containing a major mutagen(s), eluted from XAD-2 column with water, gave 3800 revertants of TA100 per plate at a dose equivalent to 10 ml of whisky.

Carcinogens occurring naturally in food

Carcinogens naturally occurring in food include metabolites of microorganisms which infect plants during harvesting and storage; products of the normal metabolism of plants and products of chemical changes occurring during processing, preservation, preparation or which are picked up from the environment, including contaminated water or soil. Some examples of these types of carcinogens are: fungal metabolites such as aflatoxins in peanuts stored under improper conditions; safrol from the oil of various plants; tannin in tea, grain and grapes; and polycyclic hydrocarbons including benzo (a) pyrene formed by smoking meat and fish. Epidemiological studies indicate that there is a high incidence of gastric cancer in the areas of the world where smoked fish are common in diets. Vitamin A may play a role in preventing the carcinogenic action of polycyclic hydrocarbons.

Fecalase: a model for activation of dietary glycosides to mutagens by intestinal flora

Many substances in the plant kingdom and in man's diet occur as glycosides. Recent studies have indicated that many glycosides that are not mutagenic in tests such as the Salmonella test become mutagenic upon hydrolysis of the glycosidic linkages. The Salmonella test utilizes a liver homogenate to approximate mammalian metabolism but does not provide a source of the enzymes present in intestinal bacterial flora that hydrolyze the wide variety of glycosides present in nature. We describe a stable cell-free extract of human feces, fecalase, which is shown to contain various glycosidases that allow the in vitro activation of many natural glycosides to mutagens in the Salmonella/liver homogenate test. Many beverages, such as red wine (but apparently not white wine) and tea, contain glycosides of the mutagne quercetin. Red wine, red grape juice, and tea were mutagenic in the test when fecalase was added, and red wine contained considerable direct mutagenic activity in the absence of fecalase. The implications of quercetin mutagenicity and carcinogenicity are discussed.