Modifying action of vegetable juice on the mutagenicity of beef extract and nitrosated beef extract

Antimutagenic and antioxidant properties of phenolic fractions from Andean purple corn (Zea mays L.)

The antimutagenic and antioxidant properties of various phenolic fractions obtained from Andean purple corn were examined by the Ames test and the DPPH antiradical assay. An anthocyanin-rich water fraction (WF) and an ethyl acetate fraction (EAF) showed a dose-dependent antimutagenic behavior against the food mutagen Trp-P-1 with IC50 values of 321.7 +/- 21.36 and 95.2 +/- 10.95 microg of chlorogenic acid equiv/plate, respectively, indicating that EAF was a more potent antimutagen. The antioxidant activities for WF and EAF were 1.019 +/- 0.05 and 0.838 +/- 0.11 microg of Trolox equiv/mug of phenolics, respectively. Further fractionation of WF and EAF revealed an ethyl acetate subfraction, EA-IV, with high antimutagen potency that contained a quercetin derivative. The mechanism of antimutagenic action of the WF is predominantly a blocking effect on the S-9 Mix activation system of the mutagen, whereas for the EAF, it is a dual mechanism involving blocking of the S-9 Mix and a scavenging action on Trp-P-1 electrophiles.

Dietary chemoprevention of clastogenic effects of 3,4-benzo(a)pyrene by Emblica officinalis Gaertn. fruit extract

Dietary supplementation with extract of fruit of Emblica officinalis Gaertn. (a rich source of vitamin C) to mice in vivo significantly reduced the cytotoxic effects of a known carcinogen, 3,4-benzo(a)pyrene. Age-matched Swiss albino mice were fed by gavaging the fruit extract daily for 28 days. From day 9, one dose of the carcinogen was given on alternate days up to a total of eight doses. On day 29, all mice were transferred to normal diet. Control sets received the extract alone, the carcinogen alone and olive oil alone. All mice were sacrificed at 12 weeks and 14 weeks after the end of the experiment. Chromosome preparations were made from bone marrow after the usual colchicine-hypotonic-fixative-air drying-Giemsa staining schedule. Cytogenetic end points screened were the frequencies of chromosomal aberrations and of damaged cells induced. The cytotoxic effects were significantly lower in the mice given the fruit extract with the carcinogen than in those given the carcinogen alone.

Chemopreventive effect of chlorophyllin on mutagenicity and cytotoxicity of 6-sulfooxymethylbenzo[a]pyrene

The chemopreventive activity of chlorophyllin (CHL) was monitored by using 6-sulfooxymethylbenzo[a]pyrene (SMBP) which is an ultimate metabolite of benzo[a]pyrene (B[a]P). CHL was quite effective in reducing both cytotoxicity and mutagenicity for SMBP in dose dependent manner up to 12.5 mM CHL in Chinese hamster V79 cells. The inhibitory patterns of CHL for SMBP were also confirmed in Salmonella typhimurium strains TA98 and TA100. Mutation frequency caused by SMBP was diminished almost to a control level at a 50 nmol CHL. A similar but less effective prevention of CHL was indicated in the mammalian and the bacterial mutagenicity assays with 6-hydroxymethylbenzo[a]pyrene (HMBP). The inhibitory effect of CHL against assault of SMBP on V79 cells was found to be related to the reduced cellular uptake of SMBP and further the remarkably lowered DNA adducts.

Chlorophyll and chromosome breakage

Increased consumption of green vegetables in the diet has been associated with protection against carcinogenic effects and related mutagenic and clastogenic (chromosome breaking) activity of genotoxic agents. Chlorophyll, present in all green plant parts, has been suggested to be a major protective factor in the process. We have, however, observed that while a crude aqueous extract of Indian spinach leaf significantly reduced genotoxic effects, chlorophyll alone was ineffective. On the other hand, chlorophyll, both as an aqueous extract from the leaf and in a purified commercial form, induced a significantly high frequency of chromosome breaks in bone marrow cells of mice on oral administration. The crude aqueous extract of the leaf was non-toxic. The protective activity of the crude leaf extract may be attributed to the total effect of the interaction between different components, in which the clastogenicity of chlorophyll has been neutralized.

In vitro effect of vegetable and fruit juices on the mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline

The antimutagenic potencies of the juices of 28 fruits and 34 vegetables commonly consumed in Germany were investigated with respect to the mutagenic activities induced by 2-amino-3-methyl[4,5-f]-quinoline (IQ), and in part by 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in Salmonella typhimurium TA98 and TA100. With IQ, weak to strong antimutagenic activities were found in 68% of the fruits and 73% of the vegetables that were tested. In fruits, strong antimutagenic activities were detected in bananas, blackberries, blueberries, sweet and sour cherries, blackcurrants and redcurrants, pineapple and watermelon. Moderate antimutagenic activities were detected in greengage, kiwi, mangos, honeydew melons and plums. Weak antimutagenic activities were detected in apple, apricot, mirabelle, pears, peaches and strawberries, whereas white and red grapes and raspberries were inactive, and gooseberries and citrus fruits in general possessed marginal or no antimutagenic activities. In vegetables, strong to moderate antimutagenic activities were found for all cruciferous vegetables, except Chinese cabbage, which had only weak antimutagenic activity. Other vegetables with strong antimutagenic activities were beets, chives, horseradish, onions, rhubarb and spinach. Moderate antimutagenic activities were found with green beans and tomatoes, weak activities in eggplant, garden cress, many lettuces, leeks, mangold, cucumber, pumpkin, radish and summer squash. Asparagus, carrots, fennel leaves, parsley, green peppers and radishes were inactive. When fruit and vegetable juices were heated, a considerable reduction of antimutagenic potencies was seen with apple, apricot, kiwi, pineapple, beets, cabbage (Chinese, Savoy, red and white), cauliflower, leafy lettuce, cucumber, onions, radish and rhubarb. Antimutagenic factors in blackberries, blueberries, sweet and sour cherries, honeydew melons, mirabelle, plums, strawberries, Brussels sprouts, chicory greens, eggplant, garden cress, mangold, pumpkin, lamb's lettuce and spinach were, however, remarkably heat stable. Antimutagenic potencies in bananas, blackcurrants and redcurrants, greengages, gooseberries, mangos, watermelon, green beans, kohlrabi, horseradish, tomatoes and chives were partially reduced. Antimutagenic activities in the juices of eight apple cultivars were moderate in two, weak in four, and marginal or absent in two. No major differences, however, were detected in five batches of oranges and three batches each of grapefruits, asparagus, green beans, broccoli, cauliflower, spinach and tomatoes. No (or only minor) differences were seen between IQ, MeIQ and MeIQx and tester strains TA98 and TA100. Pineapple and celeriac juices inhibited the enzymatic system responsible for the activation of IQ, but had no desmutagenic activity. Peroxidase activity found to be present in broccoli, cauliflower, green beans and tomatoes may contribute to antimutagenic activities in these vegetables.

Antigenotoxic properties of lactic acid bacteria in the S. typhimurium mutagenicity assay

A high percentage of human tumors is reported to be related to dietary habits. One way to improve the nutritional impact is to increase the intake of protective factors, such as inhibitors of DNA damage and other types of anticarcinogens. Specific strains of lactic acid bacteria used to ferment milk are promising candidates that may be antimutagenic and anticarcinogenic. We have studied the antimutagenicity of 10 isolated strains of beneficial lactic acid bacteria. Four types of fermented milk products were also studied for their protective properties. The effect of these bacteria on the yield of revertants induced by nitrosated beef extract was investigated in the Salmonella typhimurium mutagenicity assay. Eight of 10 isolated Lactobacillus strains reduced the yield of his+ revertants almost back to the levels of the untreated controls. Different fermented fresh yogurts containing viable bacteria (probably Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus or Lactobacillus acidophilus and Bifidobacteria) showed protective effects as well. The degree of suppressing revertants was independent of the yogurt's fat content. In contrast, yogurt products that had been heat treated were not inhibitory. The other fresh fermented milk products (e.g., buttermilk, kefir, and "Dickmilch") were not antimutagenic in this study. The results imply that some bacteria used in milk processing have an antimutagenic potential and that this property is specific for the bacterial strain.

Vegetables, fruit, and cancer. I. Epidemiology

The epidemiologic literature on the relationship between vegetable and fruit consumption and human cancer at a variety of sites is reviewed systematically. A total of 13 ecologic studies, nine cohort studies, and 115 case-control studies are included. Cancer of all sites, cancers of lung, breast, colon, rectum, esophagus, larynx, oral cavity and pharynx, stomach, pancreas, prostate, bladder, ovary, endometrium, cervix, and thyroid, as well as mesothelioma and gestational trophoblastic disease, are considered. Relevant data from clinical trials, animal, and in vitro studies are included. It is concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites. The association is most marked for epithelial cancers--particularly those of the alimentary and respiratory tracts--and, currently, is weak to nonexistent for hormone-related cancers. The association exists for a wide variety of vegetables and fruit with some suggestion that raw forms are associated most consistently with lower risk. Possible mechanisms by which vegetable and fruit intake might alter risk of cancer and possible adverse effects of vegetable and fruit consumption will be considered in Part II of this review.

The possible role of probiotics as dietary antimutagen

Possible antimutagenic actions of probiotics--mainly lactic acid bacteria--were examined using in vitro and in vivo test systems. In the Ames test with Salmonella typhimurium TA1538 beef extract and nitrosated beef extract were used as mutagens. L. casei showed high antimutagenic activity on mutagenicity induced by nitrosated beef extract only without S9 mix, whereas Omniflora (a lyophilized preparation of lactobacilli and E. coli) and its cell-free culture broth exhibited antimutagenic action only on beef extract. The actions of probiotics were more homogeneous when living animals were used in the tests. Using busulfan as a mutagen both the chromosome aberration test (with Chinese hamster bone marrow cells) and the micronucleus test (with bone marrow cells of Chinese hamsters and mice) showed strong anticlastogenic action when L. casei, Omniflora or yoghurt (with living bifiobacteria) were given orally at the same time as the mutagen. Lactobacilli were effective also after i.p. injection. Cell-free culture broths had no or only weak antimutagenic effects. Mutagen-induced chromosome aberrations and micronuclei were reduced by up to 80% by the lactobacilli.

Prevention of cancer: vegetables and plants

1. Results of epidemiological studies indicate that a human diet rich in vegetables may lower the incidence of cancer. 2. This preventive effect of the vegetable diet against cancer could be ascribed to lowered intake of energy (joules) and its content of vitamins and carotene. 3. The consumption of vegetables means also less meat and fats as well as increased fiber content and specific chemopreventive compounds (indoles, plant phenols) present in such a diet. 4. The supposed mechanisms of prevention may include enhanced enzymatic detoxification of harmful compounds, and inhibition of their binding to cellular DNA, their adsorption on fiber, detoxification of radical forms of carcinogens by natural antioxidants in plants and probably many other ways too.