Inhibition of aflatoxin B1 mutagenesis in Salmonella typhimurium and DNA damage in cultured rat and human tracheobronchial tissues by ellagic acid

Ellagic Acid and Cancer Hallmarks: Insights from Experimental Evidence

Cancer is a complex and multifaceted disease with a high global incidence and mortality rate. Although cancer therapy has evolved significantly over the years, numerous challenges persist on the path to effectively combating this multifaceted disease. Natural compounds derived from plants, fungi, or marine organisms have garnered considerable attention as potential therapeutic agents in the field of cancer research. Ellagic acid (EA), a natural polyphenolic compound found in various fruits and nuts, has emerged as a potential cancer prevention and treatment agent. This review summarizes the experimental evidence supporting the role of EA in targeting key hallmarks of cancer, including proliferation, angiogenesis, apoptosis evasion, immune evasion, inflammation, genomic instability, and more. We discuss the molecular mechanisms by which EA modulates signaling pathways and molecular targets involved in these cancer hallmarks, based on in vitro and in vivo studies. The multifaceted actions of EA make it a promising candidate for cancer prevention and therapy. Understanding its impact on cancer biology can pave the way for developing novel strategies to combat this complex disease.

Biochemical and molecular aspects of 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis: a review

1,2-dimethylhydrazine (DMH) is a member in the class of hydrazines, strong DNA alkylating agent, naturally present in cycads. DMH is widely used as a carcinogen to induce colon cancer in animal models. Exploration of DMH-induced colon carcinogenesis in rodent models provides the knowledge to perceive the biochemical, molecular, and histological mechanisms of different stages of colon carcinogenesis. The procarcinogen DMH, after a series of metabolic reactions, finally reaches the colon, there produces the ultimate carcinogen and reactive oxygen species (ROS), which further alkylate the DNA and initiate the development of colon carcinogenesis. The preneolpastic lesions and histopathological observations of DMH-induced colon tumors may provide typical understanding about the disease in rodents and humans. In addition, this review discusses about the action of biotransformation and antioxidant enzymes involved in DMH intoxication. This understanding is essential to accurately identify and interpret alterations that occur in the colonic mucosa when evaluating natural or pharmacological compounds in DMH-induced animal colon carcinogenesis.

Biochemical and molecular mechanisms underlying the chemopreventive efficacy of rosmarinic acid in a rat colon cancer

To shed light on colon cancer chemoprevention, natural phytochemicals attract researchers by virtue of their beneficial biological effects. The chemopreventive potential of rosmarinic acid (RA) was tested by using the colon carcinogen, 1,2-dimethylhydrazine (DMH) by evaluating the Aberrant crypt foci (ACF), tumour incidence, lipid peroxidative byproducts, phase I & II drug metabolizing enzymes, cell proliferative and apoptotic proteins. Rats were divided into six groups and received modified pellet diet. Group 1 served as control rats, group 2 rats received RA (5mg/kg b.w. p.o.), rats in groups 3-6 received DMH (20mg/kg b.w., s.c.) for the first fifteen weeks. In addition to DMH, groups 4-6 received RA at the dose of 5mg/kg b.w. during initiation, post initiation stages and also for the entire study period. DMH treated rats showed an increase in the development of ACF, tumour formation and multiplicity and decrease in lipid peroxidative byproducts. Moreover, it modulates xenobiotic enzymes and reduces the expressions of proapoptotic proteins; increases expressions of anti apoptotic proteins at the end of the study. Supplementation with RA to carcinogen treated rats protected them from the above deleterious effects caused by DMH and thus RA may be used as a potent chemopreventive agent.

The Effects of Ellagic Acid upon Brain Cells: A Mechanistic View and Future Directions

Ellagic acid (EA, 2,3,7,8-tetrahydroxy-chromeno; C14H6O8) is a polyphenol derived from fruits (pomegranates, berries) and nuts. EA exhibits antioxidant capacity and induces anti-inflammatory actions in several mammalian tissues. EA has been characterized as a possible neuroprotective agent, but the number of reports is still limited to conclude whether and how EA exerts neuroprotection in humans. In this regard, performing additional studies considering the potential beneficial and/or toxicological roles for EA on brain cells would be an important step towards fully understanding of when and how EA may be securely utilized by humans as a neuroprotective agent. The aim of the present work is to discuss data related to the neuronal and glial effects of EA and the mechanisms underlying such events. Moreover, future directions are suggested as a potential guide to be utilized by researchers interested in investigating the neuronal and glial actions of EA hereafter.

Ellagic acid: an unusually versatile protector against oxidative stress

Several aspects related to the antioxidant activity of ellagic acid were investigated using the density functional theory. It was found that this compound is unusually versatile for protecting against the toxic effects caused by oxidative stress. Ellagic acid, in aqueous solution at physiological pH, is able of deactivating a wide variety of free radicals, which is a desirable capability since in biological systems, these species are diverse. Under such conditions, the ellagic acid anion is proposed as the key species for its protective effects. It is predicted to be efficiently and continuously regenerated after scavenging two free radicals per cycle. This is an advantageous and unusual behavior that contributes to increase its antioxidant activity at low concentrations. In addition, the ellagic acid metabolites are also capable of efficiently scavenging a wide variety of free radicals. Accordingly, it is proposed that the ellagic acid efficiency for that purpose is not reduced after being metabolized. On the contrary, it provides continuous protection against oxidative stress through a free radical scavenging cascade. This is an uncommon and beneficial behavior, which makes ellagic acid particularly valuable to that purpose. After deprotonation, ellagic acid is also capable of chelating copper, in a concentration dependent way, decreasing the free radical production. In summary, ellagic acid is proposed to be an efficient multiple-function protector against oxidative stress.

A comparative study for the evaluation of two doses of ellagic acid on hepatic drug metabolizing and antioxidant enzymes in the rat

The present study was designed to evaluate different doses of ellagic acid (EA) in vivo in rats for its potential to modulate hepatic phases I, II, and antioxidant enzymes. EA (10 or 30 mg/kg/day, intragastrically) was administered for 14 consecutive days, and activity, protein, and mRNA levels were determined. Although the cytochrome P450 (CYP) 2B and CYP2E enzyme activities were decreased significantly, the activities of all other enzymes were unchanged with the 10 mg/kg/day EA. In addition, western-blot and qRT-PCR results clearly corroborated the above enzyme expressions. On the other hand, while the NAD(P)H:quinone oxidoreductase 1 (NQO1), catalase (CAT), glutathione peroxidase (GPX), and glutathione S-transferase (GST) activities were increased significantly, CYP1A, 2B, 2C, 2E, and 19 enzyme activities were reduced significantly with 30 mg/kg/day EA. In addition, CYP2B, 2C6, 2E1, and 19 protein and mRNA levels were substantially decreased by the 30 mg/kg/day dose of EA, but the CYP1A protein, and mRNA levels were not changed. CYP3A enzyme activity, protein and mRNA levels were not altered by neither 10 nor 30 mg/kg/day ellagic acid. These results indicate that EA exerts a dose-dependent impact on the metabolism of chemical carcinogens and drugs by affecting the enzymes involved in xenobiotics activation/detoxification and antioxidant pathways.

The effect of rosmarinic acid on 1,2-dimethylhydrazine induced colon carcinogenesis

This study was carried out to investigate the chemopreventive potential of rosmarinic acid (RA) against 1,2-dimethylhydrazine (DMH) induced rat colon carcinogenesis by evaluating the effect of RA on tumour formation, antioxidant enzymes, cytochrome P450 content, p-nitrophenol hydroxylase and GST activities. Rats were divided into six groups and fed modified pellet diet for the entire experimental period. Group 1 served as control, group 2 received RA (10 mg/kgb.w.). Groups 3-6 were induced colon cancer by injecting DMH (20 mg/kgb.w.) subcutaneously once a week for the first four weeks (groups 3-6). In addition, RA was administered at the doses of 2.5, 5 and 10 mg/kgb.w. to groups 4-6 respectively. DMH treated rats showed large number of colonic tumours; decreased lipid peroxidation; decreased antioxidant status; elevated CYP450 content and PNPH activities; and decreased GST activity in the liver and colon. Supplementation with RA (5 mgkg/b.w.) to DMH treated rats significantly decreased the number of polyps (50%); reversed the markers of oxidative stress (21.0%); antioxidant status (38.55%); CYP450 content (29.41%); and PNPH activities (21.9%). RA at the dose of 5 mg/kgb.w. showed a most pronounced effect and could be used as a possible chemopreventive agent against colon cancer.

Inhibition of aflatoxin-induced liver damage in ducklings by food additives

Inhibitory effects of food additives on toxicity induced by aflatoxin B1 was conducted in 3-day-old ducklings. Aflatoxin B1 at a dose of 5 μg/day per animal for 14 days induced severe liver damage which included necrosis, fatty changes, and biliary hyperplasia. These changes were found to be inhibited by the daily administration of turmeric (50mg), curcumin (10 mg), and ellagic acid (10 mg) in the diet. Addition of BHA-butylated hydroxy anisole (10 mg), BHT-butylated hydroxy toluene (10 mg), garlic (500 mg), and asafoetida (50 mg) inhibited necrosis and degeneration of the tissue, while biliary hyperplasia persisted. Biochemical and haematological parameters were not significantly altered under the conditions studied.

Gene expression signature of DMBA-induced hamster buccal pouch carcinomas: modulation by chlorophyllin and ellagic acid

Chlorophyllin (CHL), a water-soluble, semi-synthetic derivative of chlorophyll and ellagic acid (EA), a naturally occurring polyphenolic compound in berries, grapes, and nuts have been reported to exert anticancer effects in various human cancer cell lines and in animal tumour models. The present study was undertaken to examine the mechanism underlying chemoprevention and changes in gene expression pattern induced by dietary supplementation of chlorophyllin and ellagic acid in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by whole genome profiling using pangenomic microarrays. In hamsters painted with DMBA, the expression of 1,700 genes was found to be altered significantly relative to control. Dietary supplementation of chlorophyllin and ellagic acid modulated the expression profiles of 104 and 37 genes respectively. Microarray analysis also revealed changes in the expression of TGFβ receptors, NF-κB, cyclin D1, and matrix metalloproteinases (MMPs) that may play a crucial role in the transformation of the normal buccal pouch to a malignant phenotype. This gene expression signature was altered on treatment with chlorophyllin and ellagic acid. Our study has also revealed patterns of gene expression signature specific for chlorophyllin and ellagic acid exposure. Thus dietary chlorophyllin and ellagic acid that can reverse gene expression signature associated with carcinogenesis are novel candidates for cancer prevention and therapy.

Red raspberries have antioxidant effects that play a minor role in the killing of stomach and colon cancer cells

Berries and berry extracts possess properties that make them important in the prevention of cancer. The high antioxidant levels of these extracts play a role, but components of the berries can have other effects on cell replication and survival. We chose to test the hypothesis that (i) although the antioxidant capacity of raspberry extracts is important for inhibiting the proliferation of tumor cells, other characteristics of the berry extracts are responsible for a major part of their antiproliferative activity, and that (ii) the relative importance of the antioxidant effect can depend on the cell type being studied. The aim of this study was to assess the relative roles of low pH and high antioxidant levels in the killing of 3 cell types by an aqueous extract from Meeker red raspberries. Stomach, colon, and breast cancer cells were treated with berry extract and with HCl and ascorbic acid solutions of the same pH. A dilution of 7.5% ascorbic acid solution, of the same pH and slightly higher antioxidant concentration than the berry extract, killed less than 10% of the stomach and colon cancer cells. In contrast, the berry extract at this same dilution killed more than 90% of these cells. Antioxidants played a more significant role in the killing of breast cancer cells, however. For these cells, approximately 50% of the killing could be attributed to antioxidant effects. We conclude that the antioxidant effect plays a minor role in the killing of 2 gastrointestinal cell types, but its role in inactivating a breast cancer cell line is much more significant. No evidence of apoptosis was observed, and caspase activation did not contribute to cell killing by the extract.

Dietary berries and ellagic acid prevent oxidative DNA damage and modulate expression of DNA repair genes

DNA damage is a pre-requisite for the initiation of cancer and agents that reduce this damage are useful in cancer prevention. In this study, we evaluated the ability of whole berries and berry phytochemical, ellagic acid to reduce endogenous oxidative DNA damage. Ellagic acid was selected based on >95% inhibition of 8-oxodeoxyguosine (8-oxodG) and other unidentified oxidative DNA adducts induced by 4-hydroxy-17ss-estradiol and CuCl(2) in vitro. Inhibition of the latter occurred at lower concentrations (10 microM) than that for 8-oxodG (100 microM). In the in vivo study, female CD-1 mice (n=6) were fed either a control diet or diet supplemented with ellagic acid (400 ppm) and dehydrated berries (5% w/w) with varying ellagic acid contents - blueberry (low), strawberry (medium) and red raspberry (high), for 3 weeks. Blueberry and strawberry diets showed moderate reductions in endogenous DNA adducts (25%). However, both red raspberry and ellagic acid diets showed a significant reduction of 59% (p < 0.001) and 48% (p < 0.01), respectively. Both diets also resulted in a 3-8 fold over-expression of genes involved in DNA repair such as xeroderma pigmentosum group A complementing protein (XPA), DNA excision repair protein (ERCC5) and DNA ligase III (DNL3). These results suggest that red raspberry and ellagic acid reduce endogenous oxidative DNA damage by mechanisms which may involve increase in DNA repair.

Isolation, purification and identification of ellagic acid derivatives, catechins, and procyanidins from the root bark of Anisophyllea dichostyla R. Br

The root bark of Anisophyllea dichostyla R. Br. is traditionally used in the Democratic Republic Congo for the treatment of several conditions such as anorexia, fatigue and intestinal infections. We have identified and quantitated several polyphenol antioxidants in the methanol extract of the root bark (120g). The polyphenol content (3.32g/kg) was predominantly ellagitannins (25%) and polyhydroxyflavan-3-ols (catechins and procyanidins, 75%) with 3'-O-methyl-3,4-methylenedioxo ellagic acid 4'-O-beta-d-glucopyranoside and (-)-epicatechin as the major species in each class. These two compounds and the following species were identified unequivocally by NMR spectroscopy: (+)-catechin, (-)-epicatechin 3-O-gallate, 3-O-methyl ellagic acid, 3,3'-di-O-methyl ellagic acid, 3'-O-methyl-3,4-methylenedioxo ellagic acid, 3'-O-methyl-3,4-methylenedioxo ellagic acid 4'-O-beta-d-glucopyranoside, and 3'-O-methyl ellagic acid 4-O-beta-d-xylopyranoside. The following additional compounds were purified by semi-preparative HPLC and tentatively identified on the basis of UV spectra, HPLC-ESI-MS and nano-ESI-MS-MS: (+)-catechin-3-O-beta-d-glucopyranoside, epicatechin-(4beta-->8)-catechin (procyanidin B(1)), epicatechin-(4beta-->8)-epicatechin (procyanidin B(2)), an (epi)catechin trimer, 3-O-methyl ellagic acid 4-O-beta-d-glucopyranoside, (-)-epicatechin 3-O-vanillate, 3,4-methylenedioxo ellagic acid 4'-O- beta-d-glucopyranoside, and 3,3'-di-O-methyl ellagic acid 4-O-beta-d-xylopyranoside. Fractionation of the raw extract by column chromatography on silicic acid yielded 10 fractions. In the hypoxanthine/xanthine oxidase antioxidant assay system, CC-9 which contained a range of polyphenols dominated by (-)-epicatechin-O-gallate proved to be the most potent antioxidant fraction (IC(50)=52 micro g/mL) in terms of ROS scavenging. In terms of XO inhibition CC-8, dominated by (epi)catechin trimer and which also contained appreciable amounts of 3'-O-methyl ellagic acid 4'-O-beta-d-xylopyranoside, as well as the catechins (+)-catechin-3-O-beta-d-glucopyranoside, epicatechin-(4beta-->8)-catechin (procyanidin B(1)), and (-)-epicatechin 3-O-gallate, proved to be the most potent (IC(50)=36 micro g/mL).

Potential impact of strawberries on human health: a review of the science

Epidemiological studies have noted a consistent association between the consumption of diets rich in fruits and vegetables and a lower risk for chronic diseases including cancer and cardiovascular disease. There is accumulating evidence that much of the health-promoting potential of these plant foods may come from phytochemicals, bioactive compounds not designated as traditional nutrients. In strawberries, the most abundant of these are ellagic acid, and certain flavonoids: anthocyanin, catechin, quercetin and kaempferol. These compounds in strawberries have potent antioxidant power. Antioxidants help lower risk of cardiovascular events by inhibition of LDL-cholesterol oxidation, promotion of plaque stability, improved vascular endothelial function, and decreased tendency for thrombosis. Furthermore, strawberry extracts have been shown to inhibit COX enzymes in vitro, which would modulate the inflammatory process. Individual compounds in strawberries have demonstrated anticancer activity in several different experimental systems, blocking initiation of carcinogenesis, and suppressing progression and proliferation of tumors. Preliminary animal studies have indicated that diets rich in strawberries may also have the potential to provide benefits to the aging brain.

DNA damaging activity of ellagic acid derivatives

A strain of yeast rendered repair deficient by the conditional expression of the RAD52 locus was used to search for natural products capable of damaging DNA. Four ellagic acid derivatives, namely 3,3'-dimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (1), 3,3',4-trimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (2), 3'-methyl-3,4-O,O-methylidene ellagic acid (3) and 3'-methyl-3,4-O,O-methylidene-4'-O-beta-D-glucopyranosyl ellagic acid (4), were identified by this assay as DNA damaging natural principles from several plants, including Alangium javanicum, Anisophyllea apetala, Crypteronia paniculata, Mouririi sp. and Scholtzia parviflora. Although none of the isolated principles mediated frank strand scission of DNA in vitro, all of them potently inhibited the growth of yeast in the absence of expression of RAD52.

Ellagic acid ameliorates nickel induced biochemical alterations: diminution of oxidative stress

Nickel, a major environmental pollutant is known for its clastogenic, toxic and carcinogenic potentials. The present investigation shows that ellagic acid proves to be exceptional in the amelioration of the nickel-induced biochemical alterations in serum, liver and kidney. Administration of nickel (250 micromol Ni/kg body wt) to female Wistar rats, resulted in increase in the reduced glutathione (GSH) content [kidney (*P<0.05) and liver (**P<0.001)] and Glutathione-S-transferase (GST) and glutathione reductase (GR) activities [kidney and liver, (**P<0.001)]. Ellagic acid treatment to the intoxicated rats leads to the formation of soluble ellagic acid-metal complex which facilitates excretion of nickel from the cell or tissue, thus ameliorating nickel-induced toxicity, as evident from the down regulation of GSH content, GST and GR activities with concomitant restoration of glutathione peroxidase (GPx) activity in liver and kidney. Our data shows that ellagic acid maintains cell membrane integrity through sequestration of metal ions from the extracellular fluid, as evident from the alleviated levels of serum glutamate oxaloacetate transaminase, (SGOT), serum glutamate pyruvate transaminase (SGPT) and lactate dehydrogenase (LDH) when compared to nickel treated group. Similarly, the enhanced blood urea nitrogen (BUN) and serum creatinine levels that are indicative of renal injury showed a reduction of about 45 and 40%, respectively. The data also show that treatment of ellagic acid after 30 min of nickel administration exhibits maximum inhibition in a dose-dependent manner. In summary, our data suggests that ellagic acid act as an effective chelating agent in suppressing nickel-induced renal and hepatic biochemical alterations.

Antimutagenic effects of natural phenolic compounds in beans

Polyphenols in fruits, vegetables (e.g., flavonols like quercetin) and tea (e.g., catechins such as epigallocatechin gallate) are good antioxidants with antimutagenic and anticarcinogenic properties. In the present study, the Salmonella typhimurium tester strain YG1024 was used in the plate-incorporation test to examine the antimutagenic effect of phenolic compounds, extracted from common beans (Phaseolus vulgaris), on 1-NP and B[a]P mutagenicity. Dose-response curves for 1-NP and B[a]P were obtained; the number of net revertants/plate at the peak mutagenic dosage were 880 for 1-NP and 490 for B[a]P. For the antimutagenicity studies doses of 0.1 microg/plate and 2 microg/plate for 1-NP and B[a]P, respectively, were chosen. We obtained a dose-response curve of ellagic acid (EA) against B[a]P and 1-NP mutagenicity. To test the bean extract, a dose of 300 microg/plate of EA was chosen as the antimutagenic control. The EA and bean extracts were not toxic to the bacteria at the concentrations tested. The inhibitory effects of the bean extracts and EA against B[a]P mutagenicity were dose-dependent. The percentages of inhibition produced against B[a]P (2 microg/plate) using 300 microg/plate of EA and for the extracts 500 microg equivalent catechin/plate were 82%, 83%, 81% and 83% for EA, water extract, water/methanol extract and methanol extract, respectively. However, for 1-NP mutagenicity, only the methanolic extract from beans showed an inhibitory effect. These results suggest that common beans, as other legumes, can function as health-promoting foods.

Prevention of N-nitrosodiethylamine-induced lung tumorigenesis by ellagic acid and quercetin in mice

The polyphenolic antioxidants, consumed as an integral part of vegetables, fruits and beverages, are suggested as possessing anticarcinogenic properties. In the present study we have looked into the anticarcinogenic potential of plant polyphenols ellagic acid (EA) and quercetin against N-nitrosodiethylamine-induced lung tumorigenesis in mice. Ellagic acid was able to significantly reduce tumour incidence to 20% from the control value of 72.2%. Similarly, tumour burden was also decreased, although not significantly, from 3.15 to 2.5. Quercetin (QR) caused the tumour incidence to decrease from 76.4% to 44.4% when fed until the third dose of carcinogen. Both of the polyphenols suppressed the tumour incidence mainly by acting at the initiation phase of the carcinogenesis, since continuing the feeding of polyphenols until the termination of the experiment did not cause any apparent change in tumour incidence or tumour burden. Besides this, ellagic acid was found to be a better chemopreventor than quercetin. In order to search for their mechanism of action, the effect of feeding of these compounds on reduced glutathione (GSH), an important endogenous antioxidant, and on lipid peroxidation was investigated. Both ellagic acid and QR caused a significant increase in GSH and decrease in NADPH- and ascorbate-dependent lipid peroxidation. Ellagic acid was found to be more effective in decreasing the lipid peroxidation and increasing the GSH. This may be one of the reasons for its observed better anticarcinogenic property as compared to quercetin.

Determining efficacy of cancer chemopreventive agents using a cell-free system concomitant with DNA adduction

The large (>2000) and expanding number of natural and synthetic agents with potential cancer chemopreventive properties renders it economically and physically impossible to test each of these agents for their efficacy in the widely accepted 2-year animal bioassay and clinical trials. Therefore, there is a growing need for relevant short-term screening tests to study these compounds such that only the most efficacious ones undergo extensive long-term studies. We have previously reported in a pilot study that the use of a microsome-mediated test system concomitant with DNA adduction is a pertinent and relevant model for rapidly studying the efficacy and mechanisms of cancer chemopreventive agents. We have extended this study to investigate 26 additional agents for their potential chemopreventive abilities by studying their effects on microsome-mediated benzo[a]pyrene (BP)-DNA adduction. These agents had differential effects on the two major adducts of BP-DNA, i.e., BP-7,8-diol-9,10-epoxide (BPDE)-deoxyguanosine (dG) and 9-OH-BP-dG-derived adducts. These agents were therefore categorized into five classes. Three test agents (ellagic acid, genistein and oltipraz) were strong inhibitors of both adducts. These agents diminished BP-DNA adduction by 65-95% and were categorized as Class I agents. Six other agents (benzyl isocyanate, R(+)-1-phenylethyl isocyanate, linoleic acid ethyl ester, (+)-biotin, indole-3-carboxylic acid and beta-carotene) moderately inhibited both BP-DNA adducts (25-64%); these compounds were identified as Class II agents. Six additional test agents inhibited only one adduct selectively and nine others were ineffective; these agents were categorized as Class III and Class IV, respectively. Interestingly, seven test agents enhanced BPDE-dG or 9-OH-BP-dG or both adducts and were categorized as Class V agents. Four of these Class V agents concomitantly inhibited BPDE-dG while enhancing 9-OH-BP-dG. This emphasizes the importance of studying individual DNA adducts in contrast to total DNA binding. In conclusion, Class I and Class II agents may be good candidates for further chemoprevention studies.

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part II: Mechanism-based inhibition of rat liver microsome-mediated aflatoxin B1-DNA binding by the candidate antimutagen 7,8-diacetoxy-4-methylcoumarin

7,8-Diacetoxy-4-methylcoumarin (DAMC), with no prerequisite for oxidative biotransformation has been reported to produce suicide inactivation of microsomal cytochrome P-450-catalysed formation of aflatoxin B1-8,9-oxide that binds to DNA. Parenteral administration of DAMC to rats caused significant inhibition of AFB1 binding to hepatic DNA in vivo as well as AFB1-induced micronuclei formation in bone marrow cells. These results highlight the antimutagenic potential of DAMC.

Inhibitory effects of ellagic acid on the direct-acting mutagenicity of aflatoxin B1 in the Salmonella microsuspension assay

Ellagic acid (EA) is a phenolic compound that exhibits both antimutagenic and anticarcinogenic activity in a wide range of assays in vitro and in vivo. It occurs naturally in some foods such as strawberries, raspberries, and grapes. In the previous work, we used the Salmonella microsuspension assay to examine the antimutagenicity of EA against the potent mutagen aflatoxin B1 (AFB1) using tester strains TA98 and TA100. Briefly, the microsuspension assay was approximately 10 times more sensitive than the standard Salmonella/microsome (Ames) test in detecting AFB1 mutagenicity, and EA significantly inhibited mutagenicity of all AFB1 doses in both tester strains with the addition of S9. The greatest inhibitory effect of EA on AFB1 mutagenicity occurred when EA and AFB1 were incubated together (with metabolic enzymes). Lower inhibition was apparent when the cells were first incubated with EA followed by a second incubation with AFB1, or when the cells were first incubated with AFB1 followed by a second incubation with EA alone, all with metabolic enzymes. The result of these sequential incubation studies indicates that one mechanism of inhibition could involve the formation of an AFB1-EA chemical complex. In the present study, we further examine the effect of EA on AFB1 mutagenicity, but without the addition of exogenous metabolic enzymes. We report the mutagenicity of AFB1 in the microsuspension assay using TA98 and TA100 without the addition of S9. Neither the concentrations of AFB1 (0.6, 1.2, and 2.4 microg/tube) nor the concentrations of EA (0.3, 1.5, 3, 10, and 20 microg/tube) were toxic to the bacteria. The results indicate that AFB1 is a direct-acting mutagen, and that EA inhibits AFB1 direct-acting mutagenicity.

Modulation of the mutagenicity and metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by phenolic compounds

NNK is a potent environmental carcinogen generated during tobacco processing and smoking. The carcinogenic response to tobacco smoking is modulated by nutritional factors. In this study, liver microsomes from phenobarbital and beta-naphthoflavone-treated or control hamsters were used to assay the mutagenicity (Salmonella typhimurium TA1535) of NNK. Western analysis of these microsomal preparations revealed an increased expression of protein recognized by polyclonal antibodies specific for P-450 1A2 in beta-naphthoflavone-induced microsomes and P-450 2B1/2B2 in phenobarbital-induced microsomes. Both inducers significantly increased the mutagenicity of NNK. Metabolism of NNK by the three microsomal preparations was compared. Metabolites formed by methyl-hydroxylation of NNK by microsomes from control animals were significantly greater than those formed by alpha-methylene hydroxylation. Phenobarbital treatment had the greatest effect on alpha-methylene hydroxylation while beta-naphthoflavone had the greatest effect on methyl hydroxylation. The antimutagenic action of the polyphenolic compounds ellagic acid, esculetin and propyl gallate correlated with an inhibition of the metabolism of NNK. There were, however, differences in the effects of these compounds on specific pathways of NNK metabolism depending upon the microsomal enzyme induction treatment. This suggests that phenolic compounds have selective affinity for specific P-450 isozymes activating NNK.

Antimutagenicity of ellagic acid against aflatoxin B1 in the Salmonella microsuspension assay

Ellagic acid (EA) is a phenolic compound with antimutagenic and anticarcinogenic properties. It occurs naturally in some foods such as strawberries, raspberries, grapes, black currants and walnuts. In the present study, we used the Salmonella microsuspension assay to examine the antimutagenicity of EA against the potent mutagen aflatoxin B1 (AFB1) using tester strains TA98 and TA100. Further, we used a two-stage incubation procedure that incorporates washing the bacterial cells free of the incubation mixture after the first incubation to investigate EA and AFB1 interaction. Three different concentrations of AFB1 (2.5, 5 and 10 ng/tube) were tested against five different concentrations of EA for TA98 and TA100. EA significantly inhibited mutagenicity of all doses of AFB1 in both tester strains with the addition of S9. EA alone was not mutagenic at the concentrations tested. The greatest inhibitory effect of EA on AFB1 mutagenicity occurred when EA and AFB1 were incubated together. Lower inhibition was apparent when the cells were first incubated with EA followed by a second incubation with AFB1, and also when the cells were first incubated with AFB1 followed by a second incubation with EA alone. The results of the sequential incubation studies support the hypothesis that one mechanism of inhibition could involve the formation of a chemical complex between EA and AFB1.

The dietary anticancer agent ellagic acid is a potent inhibitor of DNA topoisomerases in vitro

Ellagic acid and 12 related agents have been tested for their ability to inhibit the activities of human DNA topoisomerase (topo) I and II. Using specific in vitro assays, we found ellagic acid and flavellagic acid to be potent inhibitors of the catalytic activities of the two topoisomerases. The minimum concentration required to inhibit > or = 50% of catalytic activity (IC50) of ellagic acid was determined at 0.6 and 0.7 micrograms/ml for topo I and topo II, respectively. Flavellagic acid's IC50 was determined at 3.0 and 3.6 micrograms/ml for topo I and topo II, respectively. Unlike topoisomerase poisons, these two plant phenols did not trap the enzyme-DNA reaction intermediate, known as the cleavable complex. In contrast, ellagic acid prevented other topo I and topo II poisons from stabilizing the cleavable complex, suggesting that the mode of its action is that of an antagonist. Structure-activity studies identified the 3,3'-hydroxyl groups and the lactone groups as the most essential elements for the topoisomerase inhibitory actions of plant phenols. On the basis of these findings and other properties of ellagic acid, a mechanistic model for the documented anticarcinogenic effects of the agent is proposed.

Polyphenols as cancer chemopreventive agents

This article summarizes available data on the chemopreventive efficacies of tea polyphenols, curcumin and ellagic acid in various model systems. Emphasis is placed upon the anticarcinogenic activity of these polyphenols and their proposed mechanism(s) of action. Tea is grown in about 30 countries and, next to water, is the most widely consumed beverage in the world. Tea is manufactured as either green, black, or oolong; black tea represents approximately 80% of tea products. Epidemiological studies, though inconclusive, suggest a protective effect of tea consumption on human cancer. Experimental studies of the antimutagenic and anticarcinogenic effects of tea have been conducted principally with green tea polyphenols (GTPs). GTPs exhibit antimutagenic activity in vitro, and they inhibit carcinogen-induced skin, lung, forestomach, esophagus, duodenum and colon tumors in rodents. In addition, GTPs inhibit TPA-induced skin tumor promotion in mice. Although several GTPs possess anticarcinogenic activity, the most active is (-)-epigallocatechin-3-gallate (EGCG), the major constituent in the GTP fraction. Several mechanisms appear to be responsible for the tumor-inhibitory properties of GTPs, including enhancement of antioxidant (glutathione peroxidase, catalase and quinone reductase) and phase II (glutathione-S-transferase) enzyme activities; inhibition of chemically induced lipid peroxidation; inhibition of irradiation- and TPA-induced epidermal ornithine decarboxylase (ODC) and cyclooxygenase activities; inhibition of protein kinase C and cellular proliferation; antiinflammatory activity; and enhancement of gap junction intercellular communication. Curcumin is the yellow coloring agent in the spice tumeric. It exhibits antimutagenic activity in the Ames Salmonella test and has anticarcinogenic activity, inhibiting chemically induced preneoplastic lesions in the breast and colon and neoplastic lesions in the skin, forestomach, duodenum and colon of rodents. In addition, curcumin inhibits TPA-induced skin tumor promotion in mice. The mechanisms for the anticarcinogenic effects of curcumin are similar to those of the GTPs. Curcumin enhances glutathione content and glutathione-S-transferase activity in liver; and it inhibits lipid peroxidation and arachidonic acid metabolism in mouse skin, protein kinase C activity in TPA-treated NIH 3T3 cells, chemically induced ODC and tyrosine protein kinase activities in rat colon, and 8-hydroxyguanosine formation in mouse fibroblasts. Ellagic acid is a polyphenol found abundantly in various fruits, nuts and vegetables. Ellagic acid is active in antimutagenesis assays, and has been shown to inhibit chemically induced cancer in the lung, liver, skin and esophagus of rodents, and TPA-induced tumor promotion in mouse skin.(ABSTRACT TRUNCATED AT 400 WORDS)

Ellagic acid protects rat embryos in culture from the embryotoxic effects of N-methyl-N-nitrosourea

Ellagic acid is a naturally occurring plant phenol that has demonstrated anticarcinogenic and antimutagenic activity in several test systems. Given the common proposed etiopathogenic processes of mutagenesis, carcinogenesis, and teratogenesis induced by genotoxic chemicals, the present study was initiated to determine whether ellagic acid would protect rat embryos in culture from the teratogenic effects of N-methyl-N-nitrosourea (MNU). Ellagic acid alone (as used in these experiments; 50 microM in DMSO) was not embryotoxic. Ellagic acid (50 microM) significantly (P less than 0.01) prevented MNU (75 microM)-induced effects including mortality (absence of heart beat), abnormal formation of the cephalic neural tube derivatives, and delayed differentiation as assessed by a morphological scoring system. These embryoprotective effects were dose responsive. Sequential treatment of embryos with ellagic acid followed by MNU in fresh media also was embryoprotective with no diminution of effect. The site at which ellagic acid interrupts the critical teratogenic events induced by MNU is apparently within the embryo and/or placenta. This model of chemical embryoprotection may be useful in determining the role of cell death and/or mutation in the teratogenic mechanism of action of methylating agents.

Antimutagenicity of ellagic acid towards the food mutagen IQ: investigation into possible mechanisms of action

The ability of the plant phenol ellagic acid to inhibit the mutagenicity of the food mutagen IQ was evaluated using Salmonella typhimurium strain TA98 in the Ames mutagenicity test. Ellagic acid caused a concentration-dependent decrease in the S-9- and microsome-mediated mutagenicity of IQ. The plant phenol did not interact directly with the IQ-derived mutagenic species and did not modify the cytosol-mediated activation of the promutagen. At the concentrations used in the mutagenicity studies, ellagic acid failed to inhibit microsomal mixed-function oxidase activity, including that mediated by the P450I family responsible for the bioactivation of IQ, despite being an essentially planar molecule as indicated by computer-graphic analysis. The inhibitory effect of ellagic acid was independent of its ability to chelate Mg2+. However, pre-incubation of ellagic acid with the bacteria, followed by removal of the plant phenol, did not completely prevent the inhibitory effect of the phenol on the mutagenicity of IQ. Intraperitoneal administration of ellagic acid to rats caused a decrease in total cytochrome P-450 levels and related activities as well as in cytosolic glutathione S-transferase activity. Finally, the possibility that the reported anticarcinogenic action of ellagic acid reflects nothing more than non-selective destruction of hepatic cytochromes P-450, and thus reduced chemical activation, is considered.

The effect of ellagic acid on xenobiotic metabolism by cytochrome P-450IIE1 and nitrosodimethylamine mutagenicity

Ellagic acid (EA) is an inhibitor of the in vitro mutagenicity of N-nitrosodimethylamine (NDMA) in Salmonella typhimurium strain TA100 using pyrazole-induced rat liver 9000 x g supernatant (S-9). In order to understand this activity, the effect of EA on the metabolic hydroxylation of 4-nitrophenol, a substrate, as is NDMA, for cytochrome P-450IIE1 was studied using pyrazole induced rat S-9 and microsomal protein. It is shown that EA has an inhibitory effect on 4-nitrophenol hydroxylase with both enzyme preparations. This effect on cytochrome P-450IIE1 may be responsible, at least in part, for the inhibition of NDMA mutagenicity by EA.

Effect of allixin, a phytoalexin produced by garlic, on mutagenesis, DNA-binding and metabolism of aflatoxin B1

Allixin, a phytoalexin isolated from garlic, was examined for its effects on aflatoxin B1(AFB1)-induced mutagenesis using Salmonella typhimurium TA100 as the bacterial tester strain and rat liver S9 fraction as the metabolic activation system. The effects of allixin on the binding of [3H]AFB1 to calf thymus DNA and on the formation of metabolites of [3H]AFB1 were also determined. Allixin showed a dose-related inhibition of Histidine+ revertants induced by AFB1. Allixin at 75 micrograms/ml inhibited [3H]AFB1 binding to calf thymus DNA and reduced formation of AFB1-DNA adducts. In addition, allixin exhibited a concentration-dependent inhibition of the formation of organosoluble metabolites and the glutathione conjugates of [3H]AFB1. The data indicate that the effect of allixin on AFB1-induced mutagenesis and binding of metabolites to DNA may be mediated through an inhibition of microsomal P-450 enzymes. Allixin may thus be useful in the chemoprevention of cancer.

The effects of ellagic acid and 13-cis-retinoic acid on N-nitrosobenzylmethylamine-induced esophageal tumorigenesis in rats

Ellagic acid (EA) and 13-cis-retinoic acid (CRA), both alone and in combination, were tested for their ability to inhibit N-nitrosobenzylmethylamine-induced tumors in the rat esophagus. Groups of male rats were fed AIN-76A diet containing EA (4 g/kg), CRA (240 mg/kg), or a combination of EA and CRA (4 g/kg and 240 mg/kg), respectively, for 25 weeks. Two weeks after initiation of the diets, NBMA (0.5 mg/kg per injection) was administered s.c. once weekly for 15 weeks. After 25 weeks on the diets, the animals were necropsied. The incidence of esophageal tumors was 97-100% in all NBMA-treated groups. The multiplicity of tumors in NBMA-treated groups was reduced significantly by EA (60%), but not by CRA, or by EA + CRA. These results demonstrate that EA and CRA do not act synergistically to inhibit NBMA-induced esophageal tumorigenesis.

Effects of capsaicin on rat liver S9-mediated metabolism and DNA binding of aflatoxin

At concentrations of 25, 50, and 100 microM, capsaicin, which is the major component in various aspects of Capsicum hot peppers, decreased the binding of aflatoxin (AFB1) to calf thymus DNA by 19%, 44%, and 71%, respectively, in incubations with rat liver S9. At concentrations of 50 and 100 microM, capsaicin decreased the formation of AFB-DNA adducts (AFB1-N7-Gua) by 53% and 75% as determined by high-pressure liquid chromatography (HPLC). HPLC analysis of organo-soluble fractions showed that these effects correlated with a concentration-dependent decrease in S9-mediated metabolism of AFB1 by capsaicin. Capsaicin also altered the formation of water-soluble conjugates of AFB1. This was indicated by a decrease in radioactivity in water-soluble fractions and in glutathione conjugates of AFB1 analyzed by HPLC. These results suggest that capsaicin inhibited the biotransformation of AFB1 by modifying Phase I hepatic enzyme activity.

Glucose alters rat liver S9-mediated mutagenesis, metabolism and DNA-binding of aflatoxin B1

The administration of 30% glucose in drinking water to rats for 48 h caused a significant increase in the hepatic S9-mediated mutagenicity of aflatoxin B1, in Salmonella typhimurium TA100 and in the binding of alfatoxin B1, to calf thymus DNA in vitro. These effects correlated with a reduction in the metabolism and detoxification of aflatoxin B1, by S9 from glucose-treated rats and suggest that the oral intake of sugar may affect the hepatocarcinogenicity of aflatoxin B1.

Inhibition of benzo[a]pyrene dihydrodiol epoxide mutagenicity by synthetic analogues of ellagic acid

Dibenzo[b, d]pyran-6-one, hydroxylated and methoxylated derivatives of this ring system, and some other analogues of the natural product ellagic acid have been synthesized and examined as inhibitors of benzo[a]pyrene dihydrodiol epoxide (BPDE) mutagenicity in Salmonella typhimurium strain TA100. Some of these new compounds have inhibitory effectiveness comparable to the natural product. On the basis of our results, we suggest qualitative rules for predicting inhibitory activity of ellagic acid analogues.

Effect of glucose administration on hamster liver S9-mediated mutagenesis, metabolism and DNA-binding of benzo[a]pyrene and aflatoxin B1

Hamster liver S9 prepared from control animals and animals given 30% glucose in drinking water 48 h before killing was used in studies of benzo[a]pyrene (BaP) and aflatoxin (AFB1)-induced mutagenesis, metabolism of BaP and AFB1, and metabolite binding to calf thymus DNA. BAP-induced mutagenesis in Salmonella typhimurium TA100 was reduced 38.5% while AFB1-induced mutagenesis was increased 36% by S9 from glucose-treated hamsters. The reduction of [3H]BaP metabolite binding to calf thymus DNA in incubations with S9 from glucose-treated hamsters correlated with a decrease in unknown BP metabolite-deoxyribonucleoside adducts isolated by high performance liquid chromatography (HPLC). Differences in the 7R and 7S-diol epoxide-1 and 2 deoxyguanosine adducts of BaP between control and glucose-treated S9 were not observed. HPLC analysis of AFB1-DNA adducts showed a 25% increase in [3H]AFB1-N7-guanine in incubations of glucose-treated S9 with [3H]AFB1 and calf thymus DNA. HPLC analysis of the organosoluble fraction of incubations with [3H]BaP and [3H]AFB1 indicated a significant effect by glucose-treated S9 on metabolism. The effect of glucose on metabolism was further reflected in the reduction of both BaP and AFB1 metabolite conjugation with glucuronide and glutathione as determined by separation on an alumina column. These results indicate that the oral administration of 30% glucose in drinking water alters hamster liver S9-mediated mutagenesis and binding of BaP and AFB1 metabolites to DNA through an effect on the metabolism of these two carcinogens.

Inhibition of liver microsome-mediated mutagenesis, metabolism and DNA-binding of benzo[a]pyrene and benzo[a]pyrene 7,8-dihydrodiol in the rat following glucose administration

Aroclor 1254-induced rat liver microsomes prepared from control and glucose-treated rats (30% glucose in drinking water 48 h prior to sacrifice) were used in studies of benzo[a]pyrene (BaP) and BaP 7,8-dihydrodiol (BaP 7,8-DHD)-induced mutagenesis in Salmonella typhimurium TA100. Microsome-dependent metabolism and metabolite binding of BaP and BaP 7,8-DHD to calf thymus DNA was also investigated. BaP-induced mutagenesis in TA100 was inhibited 27% and BaP 7,8-DHD-induced mutagenesis was inhibited 55% by microsomes from glucose-treated rats. [3H]BaP and [3H]BaP 7,8-DHD metabolite binding to DNA was inhibited 17% and 20%, respectively. High performance liquid chromatographic (hplc) analysis of enzyme-hydrolyzed DNA yielded 7R and 7S-diol epoxide-1 deoxyguanosine (BPDE-1:dG) adducts and BPDE-2:dG adducts of [3H]BaP and [3H]BaP 7,8-DHD. These adducts were inhibited 38% and 50%, respectively, by microsomes from glucose-treated rats. Hplc analysis of organosoluble metabolites of [3H]BaP and [3H]BaP 7,8-DHD showed an inhibition of metabolism of 28% and 50%, respectively, by microsomes from glucose-treated rats. The inhibition of metabolism correlated with the effect of glucose treatment on inhibition of BaP and BaP 7,8-DHD-induced mutagenesis and adduct formation. These results suggest that the mechanism by which glucose produces its effects on mutagenesis, DNA-binding and adduct formation is by an inhibition of microsome-mediated metabolism of BaP and BaP 7,8-DHD.

Antimutagenicity profiles for some model compounds

The concept of activity profile listings and plots, already applied successfully to the display of mutagenicity data, has been modified for application to antimutagenicity data. The activity profiles are bar graphs that have been organized in two general ways: for antimutagens that have been tested in combination with a given mutagen and for mutagens that have been tested in combination with a given antimutagen. Doses from both the mutagen and the antimutagen are displayed and plotted together with results on enhancement or inhibition of mutagenic activity. The short-term tests that have been used extensively to identify mutagens and potential carcinogens are increasingly being used to identify antimutagens and potential anticarcinogens. Three model mutagens, N-methyl-N'-nitro-N-nitrosoguanidine, aflatoxin B1 and benzo[a]pyrene, and 4 model antimutagens, butylated hydroxyanisole, butylated hydroxytoluene, glutathione and disulfiram, were selected from the data surveyed in the published literature. It is not clear at the present time whether the inhibition of carcinogen-induced mutation is a good indicator of anticarcinogenic properties, and further research is needed. Nevertheless, the activity profiles are useful for the assessment of the available antimutagenesis data by providing rapid visualization of considerable dose information and experimental results.

Effect of tannic acid on rat liver S9 mediated mutagenesis, metabolism and DNA binding of benzo[a]pyrene

Tannic acid, a naturally occurring plant phenol, inhibited rat liver S9 mediated mutagenesis of benzo[a]pyrene in Salmonella typhimurium by 32-77% at concentrations of 5-50 micrograms/mutagenesis plate. Tannic acid (10-40 microM) had no affect on the formation of organosoluble metabolites of benzo[a]pyrene or of its water-soluble conjugates. It did, however, inhibit benzo[a]pyrene (B[a]P) metabolite binding to calf thymus DNA by 40% at a concentration of 40 microM and inhibited benzo[a]pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE): deoxyguanosine adduct formation in calf thymus DNA by 12-54% at concentrations of 10-40 microM. These results suggest that the antimutagenic effect of tannic acid and inhibition of B[a]P metabolite binding to DNA is by a previously described scavenging mechanism and/or by a DNA-affinity binding mechanism that prevents BPDE interaction with DNA as previously described for ellagic acid.

Mechanisms of inhibitors of mutagenesis and carcinogenesis. Classification and overview

The mechanisms of action of inhibitors of mutagenesis and carcinogenesis are reviewed in the light of our present knowledge. The identified mechanisms are classified into several categories and sub-categories, depending on the stage of intervention in the mutagenesis and carcinogenesis processes, and on the patterns of modulation of the host defense devices. Although a number of the known mechanisms fit into the proposed scheme, the available information on these problems is still fragmentary, and often inhibitors act through multiple mechanisms or can interact with other inhibitors. Moreover, due to the double-edged nature of many protective factors of the organism, and to the wide array of biological properties displayed by several inhibitors, the beneficial effects are in many instances counter-balanced by adverse reactions. Nevertheless, the present data-base on mechanisms of inhibitors, which is expected to grow rapidly in the near future, provides an extremely useful scientific premise for the primary prevention of mutation-related diseases. In this prospect, the elucidation of the underlying mechanisms complements the results emerging from the monitoring of protective end-points in mutagenicity and carcinogenicity test systems.

Inhibitory effect of ellagic acid on N-2-fluorenylacetamide-induced liver carcinogenesis in male ACI/N rats

The effect of ellagic acid (EA) on the hepatocarcinogenesis induced by N-2-fluorenylacetamide (FAA) was investigated in male ACI/N rats. Rats were fed diet containing 200 ppm FAA and 400 ppm EA for 16 weeks, and diet containing 400 ppm EA alone was fed to the animals for one week before FAA exposure and one week after the carcinogen treatment. Animals were killed at intervals up to 20 weeks after cessation of the carcinogen. Liver altered foci and neoplasms were quantified using gamma-glutamyl transpeptidase reaction as well as conventional staining for identification. Exposure to FAA alone induced a substantial number of altered foci and at the end of experiment (week 36), the incidence of hepatocellular neoplasms was 100%. In the group receiving EA together with FAA, the number of altered foci was decreased at all time points and at termination, the final incidence of hepatocellular neoplasms (30%) was also reduced. Thus, EA inhibited the hepatocarcinogenesis induced by FAA when it was administered concurrently with the carcinogen.