Carboxymethyl chitin-glucan enriched diet exhibits protective effects against oxidative DNA damage induced in freshly isolated rat cells

The connection between dietary intake of carboxymethyl chitin-glucan (CM-CG, approximately 200 mg/kg body weight, during 21 days) and the response of freshly isolated rat cells to genotoxic treatment with a combination of photosensitizer Methylene Blue and visible light (MB+VL) was evaluated in presented study. Blood lymphocytes, testicular cells, and hepatocytes were isolated from rats fed by a standard or CM-CG enriched diet and in ex vivo conditions challenged with oxidative agent. Induced DNA damage was assessed using a modified comet assay. When added to the diet, CM-CG itself did not induce any negative effect on the health condition of animals or on level of DNA breaks in rat cells. Moreover, the cells isolated from CM-CG fed animals were more resistant to oxidative stress induced by visible light-excited Methylene Blue. In conclusion, we have demonstrated that carboxymethyl chitin-glucan represents a natural fungal polysaccharide that is able to exert antimutagenic properties upon application in diet.

Hydrophilic gels containing chlorophyllin-loaded liposomes: development and stability evaluation

The aim of this study was to develop and characterize hydrophilic gels containing chlorophyllin(CHL)-loaded liposomes as well as to evaluate their stability. Two different CHL-loaded liposome dispersions using non-hydrogenated and hydrogenated soybean lecithin were prepared, characterized for their particle size, polydispersity index and trapping efficiency and incorporated in Carbopol 940 NF hydrogel. The gels obtained were analyzed for flow properties, pH values and CHL content. The control liposome-free gel was obtained by incorporating the CHL solution in the hydrogel. The stability of the gels was evaluated in terms of rheological properties, pH values and CHL content during 6 months' storage at 20 +/- 2 degrees C. Suitable gel formulations for topical use were obtained revealing shear-thinning plastic flow behaviour without significant thixotropy during the whole period of examination. High yield values of the samples during the whole period indicated a long-term stability of the gel formulations. The gel formulations expressed a mild acid value acceptable for topical preparations. After 6 months' storage the CHL content was highest in the gel containing non-hydrogenated lecithin liposomes, followed by the gel containing hydrogenated lecithin liposomes and liposome-free gel, indicating that the encapsulation of CHL in liposomes led to a greater stability of CHL.

Suppression of chemical mutagen-induced SOS response by allylbenzen from Asiasarum heterotropoides in the Salmonella typhimurium TA1535/PSK1002 umu test

A methanol extract from Asiasarum heterotropoides showed a suppressive effect of the SOS-including activity on the mutagen 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with chloroform, butanol, and water. The chloroform fraction showed a suppressive effect. Suppressive compounds in the chloroform fraction were isolated by silica gel column chromatography and identified as methyleugenol (1), elemicin (2), and gamma-asaron (3) by GC/MS, IR, and 1H- and 13C-NMR spectroscopy. These compounds suppressed the MeIQ-induced SOS response in the umu test. Gene expression was suppressed 52.2, 61.8, and 71.6% at a concentration of 0.1 mM, respectively. The ID50 values (50% inhibition dose) of these compounds were 0.080, 0.028, and 0.013 mM, respectively. On the other hand, Compounds 1-3 showed weak suppressive effect of the SOS-inducing activity on activated MeIQ. These results indicate that the inhibition of the SOS-inducing activity on MeIQ, which was caused by Compound 1-3 was due to the inhibition of metabolic activity by S9.

Potent suppressive effect of green tea polyphenols on tobacco-induced mutagenicity

Antimutagenic activity of green tea (Camellia sinensis) was studied using Salmonella typhimurium strains (TA 102) (Ames test). Aqueous tobacco extract was found to be mutagenic to S. typhimurium TA 102 at concentration of 50 mg/plate. Green tea polyphenols was found to inhibit the mutagenicity of tobacco in a concentration-dependent manner. Concentrations needed for 50% inhibition of mutagen-induced revertant formation was found to be 5 mg/plate. Green tea polyphenols was also found to inhibit the urinary mutagenicity in rats induced by tobacco extract. Moreover green tea polyphenols were found to inhibit in vitro nitrosation reaction produced by reaction sodium nitrite and methyl urea and further inhibition of mutagenicity indicating that green tea has dual action to bring out a reduction in the mutagenic and carcinogenic potential of tobacco.

Evaluation of chemopreventive action and antimutagenic effect of the standardized Panax ginseng extract, EFLA400, in Swiss albino mice

In the present investigation the chemopreventive action and antimutagenic effects of a standardized Panax Ginseng extract (EFLA400, processed Panax ginseng extract containing a high titre of ginsenoside Rg3 (>3.0% w/w) known as Phoenix ginseng) in Swiss albino mice have been evaluated. The oral administration of EFLA400 at 1, 3 and 10 mg/kg body weight at pre, peri and post-initiational phases, showed significant reductions in the number, size and weight of the papillomas. A significant reduction in tumour incidence (71.41 +/- 6.73%, 72.19 +/- 4.54% and 70.46 +/- 0.38% at 1, 3 and 10 mg/kg body weight, respectively) was observed in animals in the EFLA400 treated group compared with 100% tumour incidence in the control group. The cumulative number of papillomas during an observation period of 16 weeks was significantly reduced in the EFLA400 treated group (24 +/- 0.94, 16 +/- 1.41 and 11 +/- 1.41 at 1, 3 and 10 mg/kg body weight, respectively). However, the average latent period was significantly increased from 10.81 +/- 0.1 weeks in the control group to 12.39 +/- 0.28 weeks in the treated group (10 mg/kg body weight). The average tumour weight was recorded as 128.55 +/- 8.48, 116.00 +/- 8.48 and 57.5 +/- 3.29 mg in 1, 3 and 10 mg/kg body weight EFLA400 treated groups respectively. Chromosomal aberrations and micronuclei induction was also evaluated in bone marrow cells. These genotoxicity end-points were compared with papilloma occurrence at the same dose levels of carcinogen and ginseng. In the EFLA400 treated groups significantly reduced frequencies of chromosomal aberrations and micronuclei induced by DMBA and croton oil were observed. However, the maximum decrease in the frequencies of chromosomal aberrations and micronuclei were recorded in the 10 mg/kg body weight EFLA400 treated group than that of the 1 and 3 mg/kg body weight EFLA400 treated animals. The results from the present study suggest the dose dependent effectiveness of EFLA400 in chemoprevention and antimutagenicity in Swiss albino mice.

Protective effects of ethanolic neem leaf extract on DMBA-induced genotoxicity and oxidative stress in mice

We evaluated the effects of pretreatment with ethanolic neem leaf extract on 7,12-dimethylbenz[a]anthracene (DMBA)-induced genotoxicity and oxidative stress in male Swiss albino mice. The frequency of bone marrow micronuclei, the extent of hepatic lipid peroxidation and the status of antioxidants-reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were used as intermediate biomarkers of chemoprotection. In DMBA-treated mice, the increases in micronuclei and lipid peroxides were accompanied by compromised antioxidant defenses. Pretreatment with ethanolic neem leaf extract (200 mg/kg body weight) significantly reduced DMBA-induced micronuclei and lipid peroxides and enhanced GSH-dependent antioxidant activities. The results of the present study suggest that ethanolic neem leaf extract exerts protective effects against DMBA-induced genotoxicity and oxidative stress by enhancing the antioxidant status.

Potent antioxidative and antigenotoxic activity in aqueous extract of Japanese rice bran - association with peroxidase activity

To estimate the preventive potential of Japanese rice bran (Oryza sativa japonica) against the oxygen radical-related chronic diseases such as cardio-vascular diseases and cancer, antioxidative and antigenotoxic activities of the rice bran extracts were analyzed by using assay systems for lipid peroxidation and genotoxin-induced umu gene expression. When effects of the rice bran extracts under different extraction conditions on hydroperoxide generation from auto-oxidized linoleic acid were examined using aluminum chloride method, the water extract showed strong antioxidant activity, but the methanol and acetone extracts did not exhibit significant activity. The water extract of rice bran was divided into the ethanol-precipitable (EP) and supernatant fractions, and EP fraction showed the dominant antioxidant activity, but the supernatant fraction did not exhibit significant antioxidant activity. When the effect of EP fraction on umu C gene expression in SOS response associated with DNA damage in Salmonella typhimurium (TA 1535/pSK 1002) induced by 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) was analyzed, it showed a dose-dependent suppressive activity against Trp-P-1-induced umu C gene expression. The bio-chemical analysis of EP fraction indicates that the major antioxidative and antigenotoxic activity of EP fraction is associated with a proteinous component with the molecular weight of more than 30 KDa. As a possible active principle for the antioxidative and antigenotoxic activity in EP fraction, the strong activity of an oxygen radical-scavenging enzyme, peroxidase was detected, and the purified horseradish peroxidase also caused the similar antioxidative and antigenotoxic activities. The significance of this finding is discussed from the viewpoint of the preventive role of rice bran against oxygen radical-related chronic diseases.

Randomized controlled trial of dietary intervention: association between level of urinary phenolics and anti-mutagenicity

We have undertaken a randomized trial to confirm the ability of a class of phenolics, flavonoids, to increase urinary anti-mutagenicity in smokers. Ninety heavy smokers were recruited and randomly assigned to three groups, who were given three different diets. One diet was rich in flavonoids, but not based on supplementation ('flavonoid'), one was a normal iso-caloric diet with an adequate administration of fruit and vegetables ('normal'), and one was based on supplementation of flavonoids in the form of green tea and soy products ('supplement'). The urinary anti-mutagenicity-as inhibiting effect of the urinary extracts on the mutations induced by MeIQx-was measured in Salmonella typhimurium YG1024 in the presence of liver S9 from male Sprague-Dawley rats treated with Aroclor 1254. The amount of total phenolics in the urinary extracts was measured by use of spectrometric analysis. We found that important dietary modifications can be achieved through special recipes and instructions given by a cook during an intensive course. The intervention was focused on increasing the flavonoid intake, and it was successful in that respect. In fact, differences in flavonoid intake were appreciated mainly between the first group (normal diet) and the other two (flavonoid-rich and supplemented diet), suggesting that dietary modification can be as effective as supplementation. However, both urinary anti-mutagenicity and the amounts of urinary phenolics did not change as a consequence of the trial. These results suggest that only a small fraction of urinary phenolics is influenced by dietary changes in the intake of flavonoids, and that most urinary anti-mutagens and phenolics are metabolites of dietary flavonoids, whose formation is more affected by the activity and diversity of bacterial flora in the colon than by the quantity and type of intake. A strong correlation was found between urinary phenolics and anti-mutagenicity in all the groups involved in the trial. Such correlation was not explained by dietary variables.

Antimutagenic Activity of Lipidovit

Antimutagenic properties of Lipidovit produced from the biomass of Blakeslea trispora fungi was studied by its effect on induction of chromosome aberrations by chemical mutagens dioxidine and cyclophosphamide in mouse bone marrow cells. Antimutagenic activity of Lipidovit depended on the scheme of treatment. It was maximum during pretreatment of animals (5 day) or administration in combination with mutagens (5 days). The preparation was ineffective after single administration in combination with mutagens. Lipidovit exhibited no comutagenic properties.

Antioxidative and antimutagenic activities of healthy herbal drinks from Chinese medicinal herbs

Twenty-nine Chinese medicinal herbs and three healthy herbal drinks made of those herbs in a food processing pilot plant were tested for their antioxidative, free radical scavenging, mutagenic and antimutagenic activities. Water extracts of herbs (with few exceptions) and herbal drinks showed free radical scavenging activity. All water extracts of herbs and herbal drinks showed no mutagenicity toward Salmonella typhimurium tester strains TA98 and TA100 used in the Ames mutagenic tests. In the antimutagenic tests, the mutagenic activity of 4-nitroquinoline N-oxide (NQNO) toward S. typhimurium TA98 was markedly inhibited by water extracts of herbs and herbal drinks. Based on the results, it is suggested that the herbal drinks manufactured in pilot-plant scale are safe and can be served as health-promoting drinks for the public.

No Effects of Chlorophyllin on IQ (2-Amino-3-methylimidazo[4,5-f]-quinoline)-genotoxicity and -DNA Adduct Formation in Drosophila

Previously we demonstrated that chlorophyllin suppressed the genotoxicities of many carcinogens. However, the genotoxicity of IQ (2-amino-3-methylimidazo[4,5-f]quinoline), a carcinogenic heterocyclic amine, was not suppressed in Drosophila. On the contrary, it has been reported that chrolophyllin suppressed the genotoxicity of IQ in rodents, rainbow trout and Salmonella. We demonstrated that the chlorophyllin-induced suppression of MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline)-genotoxicity was associated with a decrease in MeIQx-DNA adduct formation in Drosophila larval DNA. MeIQx represents another type of heterocyclic amine and is similar to IQ in structure. In this study we utilized (32)P-postlabeling to examine whether chlorophyllin reduced IQ-DNA adduct formation in Drosophila DNA in the same way as MeIQx. The results revealed that the formation of IQ-DNA adducts was unaffected by treatment with chlorophyllin. This was consistent with the absence of any inhibitory effect on genotoxicity as observed in the Drosophila repair test. These results suggest that IQ-behavior in Drosophila is not affected by chlorophyllin, indicating that the process of IQ-DNA adduct formation followed by expression of genotoxicity in Drosophila may be different from that in other organisms.

Effect of chrysin, a flavonoid compound, on the mutagenic activity of 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and benzo(a)pyrene (B(a)P) in bacterial and human hepatoma (HepG2) cells

The aim of the present study was to investigate the antimutagenic effects of chrysin (CR), a flavonoid compound contained in many fruits, vegetables and honey. Earlier investigations with bacterial indicators showed that CR is one of the most potent antimutagens among the flavonoids. In the present study, we tested the compound in the Salmonella strains TA98 and TA100 in combination with benzo(a)pyrene (B(a)P) and 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and found pronounced protective activity over a concentration range between 10 and 100 microg/ml. The compound itself was devoid of mutagenic activity at all concentrations tested. In the micronucleus (MN) assay with human-derived HepG2 cells, a different pattern of activity was seen. CR itself caused significant induction of MN at dose levels > or =15 microg/ml; in combination experiments with B(a)P and PhIP, U-shaped dose-response curves were obtained and protection was found only in a narrow dose range (5 - 10 microg/ml). Our findings indicate that the molecular mechanisms that account for the antimutagenic effects of CR in bacterial cells are different from those responsible for the effects in HepG2 cells. Earlier reports indicate that the antimutagenic effects of CR towards B(a)P and heterocyclic amines in bacterial indicators is due to inhibition of the activity of CYP1A. In contrast to this, we found a significant induction of CYP1A1 activity in HepG2 cells by CR. It can also be excluded that induction of GST, which is involved in the detoxification of polycyclic aromatic hydrocarbons accounts for the protective effects of CR against B(a)P since this enzyme was not significantly induced in the HepG2 cells. In the case of PhIP, induction of UDGPT and/or inhibition of sulfotransferase seen in human derived HepG2 cells after exposure to CR might play a role in the antimutagenic effects. In conclusion, our findings show that data from antimutagenicity studies with bacterial indicators cannot be extrapolated to HepG2 cells, and that CR causes genotoxic effects at higher dose levels in the latter cells. The implications of these observations for human chemoprevention strategies are discussed.

Protective effect of a polyherbal formulation (Immu-21) against cyclophosphamide-induced mutagenicity in mice

The object was to evaluate the effects of a polyherbal formulation, Immu-21, against cyclophosphamide (CP)-induced chromosomal aberrations (CA) and micronuclei (MN) in mice. CP alone (40 mg/kg, i.p.) produced classical as well as non-classical chromosomal aberrations in mice, and the incidence of CA was significantly more in the CP treated group when compared with that of the control group. Immu-21, which contains extracts of Ocimum sanctum, Withania somnifera, Emblica officinalis and Tinospora cordifolia, was given at 100 mg/kg, daily, over 7 days, and 30 mg/kg daily over 14 days and inhibited both CP-induced classical and non-classical chromosomal aberrations ( approximately 40%-60% of control). A significant increase in MN was also observed in bone marrow erythrocytes of mice treated with CP, and pretreatment with Immu-21 also significantly reduced these. Cytotoxicity was evaluated by estimating the ratio of polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs). The present results indicate that chronic treatment with Immu-21 prevented CP-induced genotoxicity in mice.

Dietary fruit and vegetables protect against somatic mutation in vivo, but low or high intake of carotenoids does not

Epidemiological studies have demonstrated protective effects of vegetables and fruit on risk of cancer, but underlying mechanisms remain unclear. Intervention studies have in some cases contradicted previous epidemiological evidence, e.g. for beta-carotene supplementation and lung cancer, emphasizing the need for mechanistic data. We assessed in vivo mutagenic effects of several dietary items using the HPRT (hypoxanthine-guanine phosphoribosyl transferase) gene assay with T-lymphocytes from 312 individuals (158 lung cancer cases, 154 population controls), who provided information on diet and smoking habits. HPRT mutant frequency (MF) was significantly decreased in relation to intake of vegetables, citrus fruits and berries, respectively, as well as calculated vitamin C intake from diet. There was a significant U-shaped association with dietary carotenoid intake, with lowest MF near population average carotenoid intakes and higher mutation frequencies both at low and high intakes, and a similar borderline significant association was observed for beta-carotene. Our study is consistent with known diet-cancer associations and provides novel human in vivo mechanistic support for a cancer-protective effect of vegetables and fruit by modulation of somatic mutagenesis. Our results also provide support for the increase in lung cancer risk observed particularly in smokers in studies of beta-carotene supplementation.

Mutagenic and antimutagenic potential of the medicinal plants M. laevigata and C. xanthocarpa

Aqueous extracts of medicinal plants (Mikania laevigata and Campomanesia xanthocarpa) were screened for the presence of mutagenic activity in the Salmonella/microsome assay. The extracts of Campomanesia xanthocarpa showed frameshift (TA97a strain) signs of mutagenic activity without exogenous metabolism (S9 fraction). The infusions of Mikania laevigata, negative for mutagenic activity, showed high percentages of inhibition of mutagenesis induced by mutagens 2AF (2-amino fluorene), in the presence of exogenous metabolism (S9 fraction), for frameshift (TA98) and base pair substitution (TA100) lesions. In addition, these inhibitions were observed against mutagen SAZ (sodium azide) in assays with the TA100 strain, without exogenous metabolism (S9 fraction). A synergistic effect was also observed in frameshift mutagenic events, with direct action in the presence of 4NQO (4-oxide-1-nitroquinoline) and a tendency to a low percentage of action enhancement, in the presence of the 2AF mutagen. The variable responses observed in the extract assays show the potentials for interaction of the different active principles in genetic material.

Therapy of glioblastoma multiforme improved by the antimutagenic chloroquine

Object

Therapy of malignant tumors is frequently curtailed by the emergence of chemoresistant cell clones. Experimentally, the authors have demonstrated that chemotherapy for glioma in rats is markedly improved by the administration of the antimutagenic quinacrine. They studied the effects of chloroquine, an antimutagenic with an optimal pharmacological profile for human use, as adjuvant for the treatment of patients with glioblastoma multiforme (GBM).

Methods

In a prospective controlled randomized trial, 18 patients with GBM underwent standard treatment with surgery, chemotherapy, and radiotherapy; nine received an additional 150-mg dose of chloroquine daily starting 1 day after surgery and continued through the observation period. Nine matched patients were included as controls. Neuroimaging studies and clinical response were periodically compared. The follow-up period ranged from 24 to 50 months.

Survival time was defined as the main outcome measure. Survival was significantly longer in chloroquine-treated patients than in controls (33 ± 5 and 11 ± 2 months, respectively [p < 0.0002]). At the end of the observation period, four patients (46%) treated with chloroquine were alive, two had evidence of tumor remission after 2 years; in another two, tumor recurrence developed after 2 and 4 years of remission, respectively. No control patient survived more than 22 months after surgery.

Conclusions

Chronic administration of chloroquine greatly enhanced the response of GBM to antineoplastic treatment. Because the cytotoxicity of chloroquine on malignant cells is negligible, these favorable results appear mediated by its strong antimutagenic effect that precludes the appearance of resistant clones during radiotherapy and chemotherapy.

Study on the mutagenicity and antimutagenicity of a natural food colour (annatto) in mouse bone marrow cells

Most manufactured foods contain chemicals added as a deliberate part of the manufacturing process. The aims of the present study were to evaluate the mutagenicity and antimutagenicity of annatto, a natural pigment extracted from the Bixa orellana L. and widely used as a colorant in foods. The micronucleus test was performed in bone marrow cells from Swiss male mice treated with one of the three concentrations of annatto (1330, 5330 and 10,670 ppm), incorporated into the diet. The animals were fed with the diets for 7 days and sacrificed 24 h after the last treatment. For the evaluation of the antimutagenic potential of annatto, at day 7, the animals received an intraperitoneal injection of cyclophosphamide (50 mg/kg body weight). Under the concentrations tested annatto did not present mutagenic or antimutagenic activities on the mice bone marrow cells. However, an increased frequency of micronucleated cells was observed when the highest concentration (10,670 ppm) was administered simultaneously with cyclophosphamide. In conclusion, the data indicate that annatto colour, for the conditions used, is neither mutagenic nor an inhibitor of induced mutations, although it should be used carefully since high doses may increase the effect of a mutagen.

Interactions betweenN-acetylcysteine and sodium selenite in modulating the clastogenicity of urethane and 2-acetylaminofluorene in mice

Combined treatment with different agents represents a promising approach in cancer chemoprevention. Therefore, it is useful to assess in preclinical models the efficacy of combinations that are selected by taking into account mechanistic considerations. We designed 2 studies evaluating the interaction between N-acetylcysteine (NAC) and sodium selenite (Se), both given with the drinking water to Balb/c mice, in modulating clastogenic effects in bone marrow polychromatic erythrocytes. In a first study, a single i.p. injection of urethane considerably enhanced the frequency of micronucleated cells. While NAC produced a significant inhibition, Se further enhanced urethane clastogenicity. When given in combination at the same doses, NAC prevented the adverse effect of Se. In a second study, a single i.p. injection of 2-acetylaminofluorene enhanced the frequency of micronucleated cells. Se did not reduce this effect to a significant extent, while NAC produced a dose-dependent inhibition. When tested at the lower dose in combination with Se, the protective effect of NAC was unchanged. Especially in association with Se, NAC also prevented the toxicity of 2-acetylaminofluorene by normalizing the ratio of polychromatic to normochromatic erythrocytes. In conclusion, NAC attenuated the clastogenicity of both urethane and 2-acetylaminofluorene and the toxicity of this aromatic amine. In addition, NAC prevented the clastogenic and toxic effects resulting from the interaction of Se with urethane. Together with the findings of previous studies, it appears that, besides its intrinsic protective properties in carcinogenesis, NAC is capable of attenuating the adverse effects of several cytotoxic drugs and chemopreventive agents.

Inhibitory effect of chlorophyllin on the frequency of micronuclei induced by sodium nitrite in mice

In this report the potency of chlorophyllin (CHL) was evaluated to prevent two types of damage produced by nitrite in mice: the increase of micronucleated polychromatic erythrocytes (MNPE) and the bone marrow toxicity, measured as the index of polychromatic erythrocytes/normochromatic erythrocytes (PE/NE). The study was done in eight groups of male mice. The first three groups were administered orally for 4 days with sodium nitrite (10, 15 and 20 mg/kg), the daily administration with nitrite was followed by an intraperitoneal administration of CHL (4 mg/kg), three more groups were administered with the same amounts of nitrite, a seventh group of mice was treated with distilled water while another was treated with CHL (4 mg/kg). Our study produced two main results: (a) no bone marrow injury was induced by any of the tested chemicals, as indicated with the PE/NE index, and (b) CHL protected (as high as 44%) the MNPE produced in nitrite treated mice.

Antimutagenic effects of black tea (World Blend) and its two active polyphenols theaflavins and thearubigins in Salmonella assays

Almost two thirds of the world population consume tea everyday. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). The antimutagenic and anticarcinogenic activities of green tea were extensively investigated compared with those of black tea. Considering the potent antimutagenic effects of green tea we recognized the need to evaluate the antimutagenic effects of black tea (World Blend Tea, Southern Tea Co., Marietta, GA) in Salmonella strains TA97a, TA98, TA100 and TA102 in preincubation tests, both with and without S9 activation. Attempts have also been made to compare the results of the tea extracts with their two active polyphenols theaflavins and thearubigins. Antimutagenicity assays were carried out in bacterial plates treated with different concentrations (1%, 2.5%, 5%, 10% and 20%) of tea extracts against known bacterial mutagens sodium azide, 4-nitro-o-phenylenediamine, cumine hydroperoxide, 2-aminofluorene and danthron. A significant decrease in the number of revertant colonies was observed in the plates treated with 1% to 20% of tea extract plus positive mutagen when compared with positive mutagen only. Both the active polyphenols theaflavins and thearubigins extracted from the black tea (World blend) also showed significant antimutagenic effects against known positive compounds in these strains. In the experiments with S9 activation, the antimutagenic effects were significantly higher. These results indicate that black tea and its two polyphenols have significant antimutagenic effects in Ames Salmonella assays.

Anti-mutagenic activity of Phyllanthus amarus Schum & Thonn in vitro as well as in vivo

Methanolic extract of Phyllanthus amarus was tested for its anti-mutagenic activity in Salmonella typhimurium strains TA1535, TA100, and TA102 (Ames test). P. amarus extract was able to inhibit the activation and mutagenicity of 2-acetaminofluorene (2-AAF) and aflatoxinB(1) at concentrations of 0.25-2 mg/plate. It was also found to inhibit mutagenicity induced by direct acting mutagens sodium azide (NaN(3)), N-methyl-N-nitro-N-nitrosoguanidine (MNNG), and 4-nitro-0-phenylenediamine (NPD), at concentrations of 1 mg to 0.25 mg/plate. Urinary mutagenicity produced in rats by benzo[a] pyrene was found to be significantly inhibited by the oral administration of Phyllanthus extract. These results indicate significant anti-mutagenicity of the extract in vitro as well as in vivo.

Search for dietary antimutagens and anticarcinogens: methodological aspects and extrapolation problems

It is well documented that dietary factors play a crucial role in the aetiology of human cancer and strong efforts have been made to identify protective (antimutagenic and anticarcinogenic) substances in foods. Although numerous studies have been published, it is problematic to use these results for the development of nutritional strategies. The aim of this article is a critical discussion of the pitfalls and problems associated with the search for protective compounds. The main obstacles in regard to the extrapolation of the data to the human situation arise from: (i) the use of inadequate experimental in vitro models, which do not reflect protective mechanisms in man and therefore give misleading results; (ii) the use of genotoxins and carcinogens that are not relevant for humans; (iii) the lack of knowledge about dose-effect relationships of DNA-protective and cancer protective dietary constituents; (iv) the use of exposure concentrations in animal models which exceed by far the human exposure levels; and finally (v) the lack of knowledge on the time-kinetics of protective effects. More relevant data can be expected from in vitro experiments with cells possessing inducible phase I and phase II enzymes, short-term in vivo models with laboratory animals which enable the measurement of effects in organs that are targets for tumour formation, and human biomonitoring studies in which endpoints are used that are related to DNA damage and cancer.