W.D. Powrie

The action of transition metals on the genotoxicity of simple phenols, phenolic acids and cinnamic acids

Simple phenols (catechol, 4-methyl catechol, resorcinol, phloroglucinol and pyrogallol), phenolic acids (p-hydroxybenzoic acid, protocatechuic acid, vanillic acid, gallic acid, syringic acid and salicylic acid), a phenylacetic acid (3,4-dihydroxyphenylacetic acid) and eugenol were assayed for clastogenic activity in Chinese hamster ovary (CHO) cells with and without the addition of a n S9 mixture, Cu2+ (10-4M) and Mn2+ (10-4M). All dihydroxylated and trihydroxylated phenolics induced chromatid breaks and exchanges. The introduction of a methyl group seems to reduce the clastogenic capacity. The addition of an S9 mixture or the transition metals Cu2+ and Mn2+ enhanced the chromosome-damaging activity in some phenolics and suppressed it in others.

A comparative genotoxicity study of chlorogenic acid (3-O-caffeoylquinic acid)

Chlorogenic acid, a compound which occurs naturally in many food items, was assayed for genotoxic activity in 3 different test systems: reverse mutations in the preincubation test with Salmonella typhimurium, gene conversion with Saccharomyces cerevisiae strain D7, and chromosome aberrations in Chinese hamster ovary (CHO) cells. Chlorogenic acid was directly convertogenic and clastogenic, but lacked a mutagenic capacity in the Salmonella bioassay. The transition metal Mn2+ enhanced the clastogenic and convertogenic activity of chlorogenic acid. In the presence of Mn2+ (10(-4)M), chlorogenic acid increased the frequency of his+ revertants in TA98 and TA100 strains of S. typhimurium. Caffeic acid and, to a lesser degree, quinic acid, which are components of chlorogenic acid, also showed genotoxic activity. The results show the importance of using several assays in combination with transition metals when testing for genotoxicity.

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.

Modified Atmosphere Packaging of Fruits and Vegetables

Consumer appeal for fresh, low-calorie, healthy, nutritious and high quality foods has grown steadily in the last 10 years. Such food trends may be attributed to consumer attitudes on lifestyle, nutrition, fitness, health and food quality [7, 103, 128, 239]. The 1990 Grocery Attitudes of Canadians study [104] indicated that 68% of grocery shoppers considered nutrition as extremely or very important. North Americans are concerned about foods in their diet in relation to weight control and chronic disease risks. Government agencies and health-promoting organizations are recommending a reduction of fat, cholesterol and salt in the diet and a greater consumption of fruits, vegetables and cereals with the view that such dietary changes may reduce the risk of heart disease and cancer incidence [7, 285]. Fresh commodities are now considered by consumers to be more nutritious than canned products and more flavourful [128].

Mutagenic activity of pyrazine derivatives: A comparative study with Salmonella typhimurium, Saccharomyces cerevisiae and Chinese hamster ovary cells

Abstract Three short-term assays were used to examine pyrazine and four of its alkyl derivatives (2-methylpyrazine, 2-ethylpyrazine, 2,5-dimethylpyrazine and 2,6-dimethylpyrazine) for the presence of mutagenic activity. Exposure of Salmonella typhimurium cultures to these compounds in an agar overlay did not result in the induction of revertants to histidine prototrophy, even when toxic doses were used. However, cultures of stationary phase Saccharomyces cerevisiae strain D5 showed an increase in aberrant colonies (but not mitotic recombinants) after exposure to each of the pyrazine compounds. Pyrazine and its derivatives all induced a significant (7- to 57-fold) increase in the frequency of chromosome aberrations (breaks and exchanges) in Chinese hamster ovary cells. These results indicate the need to use several assays and organisms when testing chemicals for the presence of mutagenic activity.

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.

Modified Atmosphere Packaging of Blueberries: Microbiological Changes

Abstract Blueberries were stored at 4°C in sealed pouches consisting of plastic films of intermediate barrier (IB) and high barrier (HB) properties. Microbial counts, headspace composition, fruit pH and soluble solids were followed with storage time. The atmosphere within the fruit packages constructed from IB film remained aerobic (6% O 2 ) with a relatively low carbon dioxide level (4% CO 2 ). Microbial growth was affected by the oxygen limitation after six weeks storage, but this storage condition could not suppress mould spoilage of the berries. In the packages constructed from the HB film, an anaerobic atmosphere developed within two weeks, and anaerobic respiration raised the carbon dioxide level to 70%. No microbial spoilage was observed in blueberries packed in HB film, even after 12 weeks storage.

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.

Clastogenic activity of dried fruits

The clastogenic activities of several commercially-dried fruits, including black and golden-seedless raisins, medium-sized California prunes, table dates, bananas, California black mission figs and breakfast apricots, were examined using Chinese hamster ovary (CHO) cells as the test organism and chromosome aberrations as the endpoint. Treatment of the CHO cells with water extracts of these dried fruits significantly increased the frequencies of metaphase plates with 1 chromosome break or exchange as well as the average number of chromosome exchanges per metaphase plate. A liver microsomal S9 mixture reduced this clastogenic activity. Dried fruits represent an example of widely consumed food products with strong genotoxic activities.

Clastogenic activity of bile acids and organic acid fractions of human feces

Chloroform extracts of fecal material from 4 subjects on normal mixed western diets were fractionated to obtain an acid fraction and a hexane extract containing neutrals and bases. The acid fraction from at least 2 of the donors induced an elevated frequency of chromosomal aberrations and exchanges in Chinese hamster ovary (CHO) cells. Since acid steroids are expected to be present in the acid fraction, 5 bile acids were assayed for clastogenic activity in CHO cells. Ursodeoxycholic acid induced chromosomal aberrations and exchanges, and this effect was enhanced by the addition of a microsomal S9 mix. However, the enhancement is probably due to physical factors rather than to enzymatic activity.