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

Ellagic Acid Prevents Binge Alcohol-Induced Leaky Gut and Liver Injury through Inhibiting Gut Dysbiosis and Oxidative Stress

Alcoholic liver disease (ALD) is a major liver disease worldwide and can range from simple steatosis or inflammation to fibrosis/cirrhosis, possibly through leaky gut and systemic endotoxemia. Many patients with alcoholic steatohepatitis (ASH) die within 60 days after clinical diagnosis due to the lack of an approved drug, and thus, synthetic and/or dietary agents to prevent ASH and premature deaths are urgently needed. We recently reported that a pharmacologically high dose of pomegranate extract prevented binge alcohol-induced gut leakiness and hepatic inflammation by suppressing oxidative and nitrative stress. Herein, we investigate whether a dietary antioxidant ellagic acid (EA) contained in many fruits, including pomegranate and vegetables, can protect against binge alcohol-induced leaky gut, endotoxemia, and liver inflammation. Pretreatment with a physiologically-relevant dose of EA for 14 days significantly reduced the binge alcohol-induced gut barrier dysfunction, endotoxemia, and inflammatory liver injury in mice by inhibiting gut dysbiosis and the elevated oxidative stress and apoptosis marker proteins. Pretreatment with EA significantly prevented the decreased amounts of gut tight junction/adherent junction proteins and the elevated gut leakiness in alcohol-exposed mice. Taken together, our results suggest that EA could be used as a dietary supplement for alcoholic hepatitis patients.

Antiproliferative and apoptotic-inducing potential of ellagic acid against 1,2-dimethyl hydrazine-induced colon tumorigenesis in Wistar rats

Colon cancer remains one of the major worldwide causes of cancer-related morbidity and mortality in Western countries and is increasingly common in Asia. Ellagic acid (EA), a major component of polyphenol possesses attractive remedial features. The aim of this study is to divulge the potential effect of EA during 1,2-dimethyl hydrazine (DMH)-induced colon cancer in male Wistar albino rats. The rats were segregated into four groups: group I, control rats; group II, rats received EA (60 mg/kg b.wt./day, orally); rats in group III, induced with DMH (20 mg/kg b.wt.) subcutaneously for 15 weeks; DMH-induced group IV rats were initiated with EA treatment. Colon of the rats treated with DMH exhibited higher glycoconjugates and proliferation index such as elevated expressions of argyrophilic nucleolar organizing regions (AgNORs), proliferating cell nuclear antigen (PCNA), cyclin D1, matrix metalloproteins (MMP-2 and -9), and mast cells. DMH induction also increased phase I-metabolizing enzymes with simultaneous decrease in the phase II detoxifying enzymes. In contrast, dietary administration of EA significantly (p < 0.05) down regulated the proliferation index and restored back the levels of biotransformation enzymes. The carcinogenic insult also altered the expression of pro-apoptotic protein p53, whereas dietary EA administration significantly (p < 0.01) up regulates p53 expression to further induce apoptotic pathway. Ultrastructural changes in colon were also in accord with the above aberrations. Overall findings suggested that the suppression of colon cancer by EA in vivo involves inhibition of cell proliferation, activation of apoptosis, and efficient detoxification.

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.

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).

Analytical methods for assay of ellagic acid and its solubility studies

Ultra-violet (UV) spectrophotometric and high performance liquid chromatographic methods for quantitative determination of ellagic acid (EA), an antioxidant were developed. The analytical methods were validated for linearity, accuracy, intra- and inter-day variability, and precision. EA was eluted using a polyethylene glycol (PEG) column with mobile phase composed of acetonitrile and 5 mM potassium dihydrogen orthophosphate buffer pH 2.5 (80:20, v/v). The UV and high performance liquid chromatography (HPLC) methods have lower detection limits of 0.2 and 0.1 microg/ml, respectively. Because of the increasing pharmaceutical interest in phytochemicals and their solubility problems, solubility studies for EA were also carried out. Various organic solvents and surfactants were screened for assessing solubility of EA and the compound was found to be soluble in some pharmaceutically acceptable solvents like triethanolamine, polyethylene glycol 400 and N-methyl pyrrollidone (NMP). Aqueous and pH dependent solubility of EA were determined using UV and HPLC methods, respectively.

Effect of naturally occurring plant phenolics on the induction of drug metabolizing enzymes by o-toluidine

Plant phenolics modify the metabolic activation of several carcinogens, including aromatic amines. In this study, we have evaluated the effects of three structurally diversified plant phenolics, protocatechuic acid (PCA), tannic acid (TA) and ellagic acid (EA) on cytochrome p450-dependent enzymes and glutathione S-transferase (GST) activities after oral administration alone or in combination with o-toluidine in rat liver and kidney. Protocatechuic and ellagic acids significantly decreased the activities of ethoxy- (EROD), methoxy- (MROD) and penthoxyresorufin (PROD) dealkylases in liver. In kidney, all phenolics inhibited only the activity of PROD. Enzyme modulation in liver correlated with CA metabolism measured in plasma. Treatment of rats with ellagic acid 1 h before o-toluidine administration diminished the activities of all hepatic alkoxyresorufine dealkylases induced by o-toluidine but increased renal EROD. In contrast to EA, protocatechuic and tannic acids increased the activities of p450-dependent enzymes in liver. All phenolics administered in combination with o-toluidine increased the activity of GST, which was reduced after the treatment with o-toluidine alone. In addition, CA metabolism in plasma resulting from oral treatment with CA was measured. The formation of CA metabolites was reduced by PCA and EA, and the metabolism of CA induced by o-toluidine was depressed by administration of all three phenolics. Our results indicate that plant phenolics, especially EA, may modulate the genotoxic effects of o-toluidine by modifying pathways leading to the formation of its reactive metabolite. Moreover, as the result of CYP1A modification these compounds may affect the metabolism of CA.

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.

Therapeutic potential of dietary phase 2 enzyme inducers in ameliorating diseases that have an underlying inflammatory component

Many diseases associated with ageing have an underlying oxidative stress and accompanying inflammatory component, for example, Alzheimer's disease or atherosclerosis. Reviewed in this manuscript are: the role of oxidative stress in activating the transcription factor nuclear factor kappa B (NFκB), the role of NFκB in activating pro-inflammatory gene transcription, strong oxidants produced by cells, anti-oxidant defense systems, the central role of phase 2 enzymes in the anti-oxidant defense, dietary phase 2 enzyme inducers and evidence that dietary phase 2 enzymes decrease oxidative stress. It is likely that a diet containing phase 2 enzyme inducers may ameliorate or even prevent diseases that have a prominent inflammatory component to them. Research should be directed into the potential therapeutic effects of dietary phase 2 enzyme inducers in ameliorating diseases with an underlying oxidative stress and inflammatory component to them.Key words: Alzheimer's disease, atherosclerosis, diet, glutathione, inflammation, stroke.

The effects of ellagic acid on arylamine N-acetyltransferase activity in the bacterium Pseudomonas aeruginosa

Arylamine N-acetyltransferase (NAT) activity in Pseudomonas aeruginosa was inhibited by ellagic acid (EA), a naturally occurring dietary plant phenol. By measuring the acetylation of 2-aminofluorene (2-AF), the NAT activity was determined. In P. aeruginosa ATCC 27853, a NAT activity of 1.37 +/- 0.25 nmol/min/10(10) CFU for intact cell and a NAT activity of 5.92 +/- 0.20 nmol/min/mg protein for cytosolic preparation were measured. EA (ranging from 1 to 0.125 mM) showed a dose-dependent inhibition of NAT activities in the analysis of both intact cell and cytosolic preparations. Enzymatic kinetics were determined and found that EA was a potent non-competitive inhibitor of NAT activity in P. aeruginosa ATCC 27853. EA inhibition of NAT activities in P. aeruginosa ATCC 27853 was time-dependent for at least 4 hrs. These data strongly indicated that EA could suppress NAT activity in P. aeruginosa.

Tannins, xenobiotic metabolism and cancer chemoprevention in experimental animals

Tannins are plant polyphenolic compounds that are contained in large quantities in food and beverages (tea, red wine, nuts, etc.) consumed by humans daily. It has been shown that various tannins exert broad cancer chemoprotective activity in a number of animal models. This review summarizes the recent literature regarding both the mechanisms involved, and the specific organ cancer models used in laboratory animals. An increasing body of evidence demonstrates that tannins act as both anti-initiating and antipromoting agents. In view of the fact that tannins may be of valid medicinal efficacy in human clinical trials, the present review attempts to integrate results from animal studies, and considers their possible application in humans.

Biodistribution of, antimutagenic efficacies in Salmonella typhimurium of, and inhibition of P450 activities by ellagic acid and one analogue

Ellagic acid (EA) is generated by hydrolysis of ellagitannins present in fruit berries and edible nuts and grapes. Large doses of EA prevent lung tumorigenesis induced by the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. In this study, we document the efficacies of the EA structural analogue (3,4,7,8-tetrahydroxy-6H-benzo[b,d]pyran-6-one) (analogue 1) to inhibit specific P450 activities, pulmonary metabolism of NNK in A/J mice, and NNK-induced mutations in Salmonella typhimurium. Mouse lung microsomes metabolized benzyloxyresorufin, a marker of cytochrome P450 2B1 activity, more extensively than methoxyresorufin or ethoxyresorufin. The EA analogue was more effective than EA in inhibiting dealkylation of the three alkoxyresorufins, suggesting that it is a nonspecific inhibitor of P450s. Mouse lung microsomes hydroxylate testosterone in the 7alpha and 6beta positions, suggesting contributions of P450 2A1 and P450 3A2 isozymes, respectively. Inhibition of both pathways was more effective with the EA analogue than with EA. Mouse lung explants metabolized NNK by alpha-carbon hydroxylation (activation) and pyridine N-oxidation (deactivation). Both pathways were inhibited when 100 microM EA was added to the culture medium. The EA analogue was a better inhibitor of the activation of NNK to electrophilic species than EA. Mouse lung microsomes activate NNK to intermediates mutagenic to S. typhimurium. Inhibition of NNK mutagenicity by EA or the EA analogue was 20 or 65%, respectively. The distribution of the EA analogue in lung and liver was determined following gavage with 1.7 mmol of the EA analogue. In the lung, a maximal level of EA analogue corresponding to 105 nmol was observed 30 min after administration of the analogue. The level in liver tissues was 4-fold lower than in the lung. Results of this study demonstrate that the EA analogue is more effective than EA in inhibiting the pulmonary activation of NNK and suggest that the EA analogue could be effective in preventing lung tumorigenesis.

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.

Validation of 4-nitrophenol as an in vitro substrate probe for human liver CYP2E1 using cDNA expression and microsomal kinetic techniques

The involvement of human cytochrome P450 (CYP) 2E1 in the hydroxylation of 4-nitrophenol (4NP) to 4-nitrocatechol (4NC) has been investigated using cDNA expression and liver microsomal kinetic and inhibitor techniques. 4NP hydroxylation by human liver microsomes and cDNA-expressed human CYP2E1 exhibited Michaelis-Menten kinetics; the respective apparent Km values were 30 +/- 7 and 21 microM. Mutual competitive inhibition was observed for 4NP and chlorzoxazone (CZ) (an alternative human CYP2E1 substrate) in liver microsomes, with close similarities between the calculated apparent Km and Ki values for each individual compound. 4NP and CZ hydroxylase activities in microsomes from 18 liver donors varied to a similar extent (3.3- and 3.0-fold, respectively) and 4NP hydroxylase activity correlated significantly (rs > or = 0.75, P < 0.005) with both CZ hydroxylation and immunoreactive CYP2E1 content. The prototypic CYP2E1 inhibitor, diethyldithiocarbamate, was a potent inhibitor of 4NC formation and decreased 4NP hydroxylation by cDNA-expressed CYP2E1 and human liver microsomes in parallel. Probes for other human CYP isoforms namely (alpha-naphthoflavone, coumarin, sulphaphenazole, quinidine, troleandomycin and mephenytoin) caused < 15% inhibition of liver microsomal 4NP hydroxylation. These data confirm that, as in animal species, 4NP hydroxylation is catalysed largely by CYP2E1 in human liver and 4NP may therefore be used as an in vitro substrate probe for the human enzyme.