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PubMed1994

Inhibitory effects of plant polyphenols on rat liver glutathione S-transferases.

Several novel naturally occurring flavonoids and other polyphenols exerted varying degrees of concentration-dependent inhibition on uncharacterized rat liver glutathione S-transferase (EC 2.5.1.18, GST) isoforms. The order of inhibitory potencies of the five most potent polyphenols was tannic acid > 2-hydroxyl chalcone > butein > morin > quercetin, and their IC50 values were 1.044, 6.758, 9.033, 13.710 and 18.732 microM, respectively. Their inhibitions were reversible, as indicated by dialysis experiments. The optimum pH for the inhibitions by four of the compounds (tannic acid, butein, 2-hydroxyl chalcone and morin) was in the range of pH 6.0 to 6.5, but for quercetin the optimum pH was 8.0. These potent inhibitors possess one or more of the following chemical structural features: (a) polyhydroxylation substitutions, (b) absence of a sugar moiety, (c) for the chalcones, the presence of an open C-ring and hydroxylation at either the C-2 or C-3 position, (d) for the flavonoids, the attachment of the B-ring to C-2, and (e) a double bond between C-2 and C-3. Butein exhibited a non-competitive inhibition toward both glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). Interestingly, tannic acid showed a non-competitive inhibition toward CDNB but a competitive inhibition toward GSH. The inhibitory potency of tannic acid on rat liver GSTs was concentration and substrate dependent. Using CDNB, p-nitrobenzyl chloride, 4-nitropyridine-N-oxide, and ethacrynic acid as substrates, the IC50 values for tannic acid were 1.044, 11.151, 20.206, and 57.664 microM, respectively.

Animals↗
PubMed1995

Inhibition of 1,2,4-benzenetriol-generated active oxygen species and induction of phase II enzymes by green tea polyphenols.

Autooxidation of polyphenolic metabolites of benzene, such as hydroquinone (HQ), catechol (CT), 1,2,4-benzenetriol (BT) and pyrogallol (PG), produced several kinds of active oxygen species (AOS). BT and PG induced DNA breaks in the absence of metal ions, especially when producing AOS such as H2O2, O2-, HO. or 1 delta gO2. HQ and CT did not result in double-strand DNA breaks, except when ferrous ion was added, indicating the participation of the Fenton reaction. Polyphenolic fractions isolated from green tea (GTP) exerted inhibitory effects on the autooxidation of BT and suppressive effects on H2O2 or HO. generated from phenolic metabolites of benzene in the presence of S9 or an in vivo system. Additionally, although the activities of antioxidant and phase II enzymes were elevated by both GTP and phenolic metabolites of benzene, GTP counteracted the lowering GSH caused by phenolic metabolites of benzene in rat liver. The above results suggest that GTP and phenolic metabolites of benzene are antagonistic in their response to AOS, especially hydroxyl radical.

Animals↗
PubMed1986

Effects of plant-derived flavonoids and polyphenolic acids on the activity of mutagens from cooked food.

The ability of 3 plant flavonoids (morin, myricetin and quercetin) and 4 polyphenolic acids (caffeic acid, chlorogenic acid, ellagic acid and ferulic acid) to inhibit the genotoxic effects of a number of cooked-food mutagens (IQ, MeIQ, MeIQx, Trp-P-1 and Trp-P-2), was investigated in a bacterial mutation assay using Salmonella typhimurium TA98 as indicator and hepatic S9 mixes from either SWR mice or Syrian hamsters as metabolic activating systems. Although the polyphenolic acids failed to have an effect, the flavonoids generally inhibited IQ, MeIQ, MeIQx and Trp-P-1 induced mutagenesis in a dose-dependent manner, irrespective of the source of S9. This was not the case with Trp-P-2 where the flavonoids were only observed to inhibit when SWR mouse S9 but not Syrian hamster S9 was used. Of the 3 compounds, myricetin and quercetin were superior to morin in their inhibitory capacity.

Animals↗
PubMed1991

Loss of heterocyclic amine mutagens by insoluble hemicellulose fiber and high-molecular-weight soluble polyphenolics of coffee.

The presence of 2 kinds of components in brewed and instant coffee that could remove and destroy heterocyclic amine mutagens was demonstrated. The component that could remove the mutagens was insoluble fiber composed of hemicellulose. The fiber could tightly adsorb the mutagens Trp-P-1, Trp-P-2, Glu-P-1 and A alpha C, and those generated in roasted coffee beans. The component that could destroy the mutagens was high-molecular-weight soluble polyphenolics. They might be converted into quinone derivatives in the presence of molecular oxygen. The quinone derivatives might destroy the mutagens. The fibers and the polyphenolics in one cup of brewed or instant coffee had the capacity to remove and destroy a substantial amount of the mutagens in pyrolysates of foodstuffs.

Amines↗
PubMed1990

Biochemical response of Norway spruce (Picea abies (L.) Karst.) towards 14-month exposure to ozone and acid mist: part I--Effects on polyphenol and monoterpene metabolism.

Three-year-old clonal Picea abies (L.) Karst. plants, grown either on a sandy (No. 1) or on a calcareous (No. 2) soil, were treated with ozone (100 microg m(-3) and peaks of up to 360 microg m(-3)) and acid mist (pH 3.0) over two vegetation periods. Needles of the current (1987) and previous (1986) year were analysed at the end of the experiment for biosynthetic enzymes and in vivo activity of the phenylpropanoid pathway, for products of polyphenol metabolism (clones 11 and 14), and for mono- and sesquiterpenes (clones 14 and 16). 1. Polyphenol metabolism. The activity of cinnamyl alcohol dehydrogenase, an enzyme of the lignin pathway, was increased by the treatment by up to 83% in the needles of both age classes. Chalcone synthase was measured in mature tree material for the first time. This enzyme, as well as phenylalanine ammonia-lyase activities and the content of catechin, astringin, isorhapontin, picein and p-hydroxyacetophenone, exhibited no significant treatment-dependent differences. However, soil and age-class dependent differences occurred. Pulse-labelling experiments with l[U-(14)C]phenylalanine and [2-(14)C]acetate were carried out at four different stages of shoot development and showed label incorporation into (+)-catechin and proanthocyanidins. There was no effect of the ozone and acid mist treatment. 2. Monoterpenes. The content of needle terpenes was generally diminished by the ozone and acid mist treatment. Other factors tested, such as clone, needle age and soil, exerted a highly significant influence on the content of most of the needle monoterpenes.

Journal Article↗
PubMed1993

In vitro effects of natural plant polyphenols on the proliferation of normal and abnormal human lymphocytes and their secretions of interleukin-2.

The growth of two human lymphoid tissue derived cell lines, IM-9 and Molt-4 cells together with normal lymphocytes was studied in the presence of several plant natural products. Amongst the 11 test compounds studied, the flavonoids (fustin, taxifolin, phloretin) and the polyphenol tannic acid were potent inhibitors. At concentrations ranging from 10-50 microM they exerted varying degrees of inhibition on Molt-4 cell and normal lymphocyte cell proliferation but not on the non-malignant (IM-9) cells. The order of potency was tannic acid > phloretin > taxifolin > fustin. The IL-2 level was also enhanced in the Molt-4 but inhibited in normal lymphocytes. However, its level remained unchanged in the IM-9 cells. The amount of IL-2 secreted could be directly correlated to the percentage cell growth inhibition for only Molt-4 cells. Interestingly, our findings suggest the possibility of exploiting the natural plant polyphenols for their possible use in the treatment of lymphocyte malignancy.

Cell Division↗
PubMed1994

Prevention of heterocyclic amine formation by tea and tea polyphenols.

Heterocyclic amines (HCAs), formed during the cooking of meats and fish, are thought to be the genotoxic carcinogens associated with important types of human cancer in meat-eating populations, such as cancer of the breast, colon or pancreas. We studied the effect of black or green tea, and of the tea polyphenols theaflavine gallate (TFG, black tea) and epigallocatechin gallate (EGCG, green tea) on the formation of typical HCAs, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), using the model in vitro systems of Jägerstad. Green tea and black tea and solutions of TFG and EGCG lower the formation of PhIP by 62-85% during 1 h heating at 160 degrees C of 1 mmol creatinine, 1 mmol phenylalanine and 0.5 mmol glucose in 3.3 ml diethylene glycol-water (10:1), where the inhibitors replaced 0.3 ml of the water. The production of MeIQx and related HCAs, in the same system but with 1 mmol glycine instead of phenylalanine was likewise reduced, determined by amounts of mutagens formed. In the latter systems, the teas were not, or less effective, but the polyphenols were inhibitory. Thus, the tea products represent another approach to lower the formation of HCAs.

Antineoplastic Agents↗
PubMed2006

Antiproliferative and apoptosis inducing effect of lactoferrin and black tea polyphenol combination on hamster buccal pouch carcinogenesis.

Combination chemoprevention using tea polyphenols as one of the components has received growing consideration in recent years. The present study was designed to evaluate the antiproliferative and apoptosis inducing effects of bovine lactoferrin (bLF) and black tea polyphenol (Polyphenon-B: P-B) combination on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Topical application of DMBA for 14 weeks induced buccal pouch tumours that showed aberrant expression of cytokeratins, a marker for epithelial carcinomas. This was associated with increased cell proliferation and evasion of apoptosis as revealed by upregulation of proliferating cell nuclear antigen, NF-kappaB, mutant p53, Bcl-2 and downregulation of Bax, Fas and caspase 3 protein expression. Although dietary administration of bLF and Polyphenon-B alone significantly reduced tumour incidence, combined administration of bLF and Polyphenon-B was more effective in inhibiting HBP carcinogenesis by restoring normal cytokeratin expression, inhibiting cell proliferation and inducing apoptosis. These findings suggest that a "designer item" approach will be useful for human oral cancer prevention strategies.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2004

Polyphenol (-)-epigallocatechin gallate inhibits apoptosis induced by irradiation in human HaCaT keratinocytes.

Green tea is a rich source of polyphenols, and (-)-epigallocatechin-3-gallate (EGCG) is a major constituent of green tea polyphenols. In the present study, we investigated the effect of EGCG on apoptosis induced by irradiation in the human keratinocytic cell line HaCaT. Irradiation by gamma-ray induced apoptosis with concomitant cleavage of caspase-3 and its in vivo substrate poly(ADP-ribose) polymerase. Treatment of cells with EGCG inhibited irradiation-induced apoptosis as detected by Hoechst staining and internucleosomal cleavage of DNA, and prevented the cleavage of these proteins by irradiation. We also found that the treatment of cells with EGCG alone suppressed cell growth and induced apoptosis in these cells. Our results suggest that EGCG inhibits irradiation-induced apoptosis by inactivating the caspase pathway in HaCaT cells. Our study also indicates that EGCG has a dual effect on the survival of these keratinocytes.

Apoptosis↗
PubMed2005

Suppression of tumor cell invasiveness by hydrolyzable tannins (plant polyphenols) via the inhibition of matrix metalloproteinase-2/-9 activity.

Elevated expression of matrix metalloproteinases (MMPs), especially that of MMP-2 and MMP-9, is associated with increased metastatic potential in many tumor cells. Recently, green tea polyphenol epigallocatechin-3-O-gallate (EGCG) has been shown to inhibit the MMP-2/-9 activity as well as the invasiveness of tumor cells. In this study, we have examined the inhibitory effect of hydrolyzable tannins (plant polyphenols) on the tumor cell invasion. Our results demonstrate that beta-d-glucose whose hydroxy groups are substituted entirely with galloyl group and further some of them are cross-linked to form hexahydroxydiphenoyl group, for example, suppresses the invasiveness of tumor cells much more potently than EGCG via direct inhibition of the MMP-2/-9 activity. Among those examined, 1,2,4-tri-O-galloyl-3,6-hexahydroxydiphenoyl-beta-d-glucose (punicafolin) inhibits the invasion of HT1080 fibrosarcoma cells most potently. These hydrolyzable tannins would provide new leads for the development of potent inhibitors against tumor metastasis.

Animals↗
PubMed2006

ABTS radical-driven oxidation of polyphenols: isolation and structural elucidation of covalent adducts.

The formation of covalent adducts obtained from the reaction of the polyphenols, trans-3,3',4',5,7-pentahydroxyflavan (catechin) and 1,3,5-trihydroxybenzene (phloroglucinol), with ABTS radicals is reported. Two adducts derived from (+)-catechin and three adducts from phloroglucinol were isolated and identified using reversed-phase high performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS). The molecular masses of the (+)-catechin-derived adducts (I(c) and II(c)) were found to be 802 and 559 Da, respectively, whereas the masses of phloroglucinol-derived adducts (I(p), II(p), and III(p)) were 638, 395, and 381 Da, respectively. The initially formed adducts (I(c), I(p)) were unstable and degraded to secondary adducts (II(c), II(p), and III(p)) releasing part of the ABTS molecule. The structures of these adducts were elucidated by interpreting the results of MS/MS analysis of prominent ions generated by both positive and negative ion ESI-MS. The adducts were found to scavenge ABTS radicals, an observation that could explain the complex kinetic behaviour manifested by the reactions of ABTS radicals with polyphenols. A mechanism, which accounts for both the formation of the adducts and the degradation products of ABTS radicals, is proposed.

Benzothiazoles↗
PubMed2006

Preparation of biosensors by immobilization of polyphenol oxidase in conducting copolymers and their use in determination of phenolic compounds in red wine.

Electrochemically produced graft copolymers of thiophene capped polytetrahydofuran (TPTHF1 and TPTHF2) and pyrrole were achieved by constant potential electrolysis using sodium dodecylsulfate (SDS) as the supporting electrolyte. Characterizations were based on Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Electrical conductivities were measured by the four-probe technique. Novel biosensors for phenolic compounds were constructed by immobilizing polyphenol oxidase (PPO) into conducting copolymers prepared by electropolymerization of pyrrole with thiophene capped polytetrahydrofuran. Kinetic parameters, maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) and optimum conditions regarding temperature and pH were determined for the immobilized enzyme. Operational stability and shelf-life of the enzyme electrodes were investigated. Enzyme electrodes of polyphenol oxidase were used to determine the amount of phenolic compounds in two brands of Turkish red wines and found very useful owing to their high kinetic parameters and wide pH working range.

Biosensing Techniques↗
PubMed2006

Anxiolytic properties of green tea polyphenol (-)-epigallocatechin gallate (EGCG).

Naturally occurring polyphenols are potent antioxidants. Some of these compounds are also ligands for the GABA(A) receptor benzodiazepine site. This feature endows them with sedative properties. Here, the anxiolytic activity of the green tea polyphenol (-)-epigallocatechin gallate (EGCG) was investigated after acute administration in mice, using behavioral tests (elevated plus-maze and passive avoidance tests) and by electrophysiology on cultured hippocampal neurons. Patch-clamp experiments revealed that EGCG (1-10 muM) had no effect on GABA currents. However, EGCG reversed GABA(A) receptor negative modulator methyl beta-carboline-3-carboxylate (beta-CCM) inhibition on GABA currents in a concentration dependent manner. This was also observed at the level of synaptic GABA(A) receptors by recording spontaneous inhibitory synaptic transmission. In addition, EGCG consistently inhibited spontaneous excitatory synaptic transmission. Behavioral tests indicated that EGCG exerted both anxiolytic and amnesic effects just like the benzodiazepine drug, chlordiazepoxide. Indeed, EGCG in a dose-dependent manner both increased the time spent in open arms of the plus-maze and decreased the step-down latency in the passive avoidance test. GABA(A) negative modulator beta-CCM antagonized EGCG-induced amnesia. Finally, state-dependent learning was observable after chlordiazepoxide and EGCG administration using a modified passive avoidance procedure. Optimal retention was observed only when animals were trained and tested in the same state (veh-veh or drug-drug) and significant retrieval alteration was observed in different states (veh-drug or drug-veh). Moreover, EGCG and chlordiazepoxide fully generalized in substitution studies, indicating that they induced indistinguishable chemical states for the brain. Therefore, our data support that EGCG can induce anxiolytic activity which could result from an interaction with GABA(A) receptors.

Animals↗
PubMed2005

The tea polyphenols EGCG and EGC repress mRNA expression of human telomerase reverse transcriptase (hTERT) in carcinoma cells.

Tea polyphenols have inhibitive effects for carcinogenesis. A reporter system controlled by hTERT promoter was constructed to evaluate the effects of tea polyphenols, (-)-epigallocatechin-3-gallate (EGCG) and (-)-epigallocatechin (EGC) on the repression of hTERT transcription. The hTERT promoter activity was selectively repressed by 20-40 microM EGCG and EGC in a dose- and time-dependent manner. Real-time RT-PCR confirmed that the endogenous hTERT mRNA level was decreased in H1299, OECM-1 and SAS cells treated with EGCG or EGC. Our results identified the repression activities of EGCG and EGC toward telomerase expression that might be linked to inhibition of carcinoma cell growth. This cell-based reporter system is useful for screening drugs targeting hTERT repression.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Comparative evaluation of the chemopreventive efficacy of green and black tea polyphenols in the hamster buccal pouch carcinogenesis model.

OBJECTIVES: To evaluate the comparative chemopreventive efficacy of green tea polyphenols (Polyphenon-E) and black tea polyphenols (Polyphenon-B) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. DESIGN AND METHODS: Hamsters were divided into 6 groups. Animals in group 1 served as controls. Animals in groups 2 and 3 were administered 0.05% Polyphenon-E and B, respectively, in the diet. The right buccal pouches of animals in groups 4-6 were painted with 0.5% DMBA three times a week for 14 weeks. While group 4 received no further treatment, hamsters in groups 5 and 6 received diet containing 0.05% Polyphenon-E and B, respectively. The status of carcinogen-metabolising enzymes, lipid peroxidation and glutathione-dependent antioxidants in the buccal pouch and liver, as well as the frequency of bone marrow micronuclei were used as biomarkers. RESULTS: Application of DMBA induced HBP carcinomas, increased genotoxicity with an imbalance in carcinogen-metabolising enzymes and the cellular redox status. Inhibition of HBP carcinomas by Polyphenon-E and B was associated with a significant decrease in phase I enzymes, modulation of lipid peroxidation and enhanced antioxidant and phase II enzyme activities. CONCLUSION: The greater efficacy of Polyphenon-B in inhibiting HBP carcinogenesis suggests that it may have a major impact in the chemoprevention of oral cancer.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2005

Tea polyphenol epigallocatechin 3-gallate impedes the anti-apoptotic effects of low-grade repetitive stress through inhibition of Akt and NFkappaB survival pathways.

V79 Chinese Hamster lung fibroblasts were subjected to repetitive low-grade stress through multiple exposures to 30 microM H2O2 in culture for 4 weeks. Akt/protein kinase B became phosphorylated at serine473 and threonine308 during this period of repetitive stress. Concurrent exposure of the cells to LY294002 (5 microM), a phosphoinositide-3 kinase inhibitor or 4.5 microM epigallocatechin 3-gallate (EGCG), a tea polyphenol almost completely blocked Akt activation by repetitive stress. Phosphorylation of I kappa B kinase (IKK) and transcriptional activity driven by nuclear factor kappa B (NFkappaB) were significantly enhanced by repetitive oxidative stress. These increases were largely abolished by simultaneous exposure to EGCG. The repetitively stressed cells demonstrated a significant resistance to apoptosis by subsequent acute stress in the form of ultraviolet radiation at 5 J/m2 or H2O2 (7.5 mM). The resistance to apoptosis conferred by repetitive stress was drastically reduced (>80%) by constant exposure to EGCG during the stress period while the presence of LY294002 or the NFkappaB inhibitor SN50 brought about a relatively moderate effect (about 50-65%). Our data indicate that activation of Akt and NFkappaB pro-survival pathways by repetitive low-grade stress results in a strong inhibition of the normal apoptotic response after subsequent acute stress. The tea polyphenol EGCG impedes the activation of both Akt and NFkappaB by repetitive stress and as a result preserves the normal apoptotic response during subsequent acute stress.

1-Phosphatidylinositol 4-Kinase↗
PubMed2005

Estrogenic activity of a polyphenolic extract of the leaves of Epimedium brevicornum.

The estrogenic activity of a polyphenolic extract of the leaves of Epimedium brevicornum and five fractions obtained by solid-phase extraction were investigated using estrogen-responsive bioassays, a yeast cell assay and the Ishikawa Var-I assay. The extract was found to exhibit significant estrogenic activity in both assays. Furthermore, bioassay-guided fractionation led to localisation of the estrogenicity in the relatively non-polar fractions of the polyphenolic extract.

Dose-Response Relationship, Drug↗
PubMed2005

Divergent effects of resveratrol, a polyphenolic phytostilbene, on free radical levels and type of cell death induced by the histone deacetylase inhibitors butyrate and trichostatin A.

We investigated the effects of the polyphenolic phytostilbene resveratrol on the steady-state free radical (FR) concentration and mode of cell death induced by the histone deacetylase inhibitors butyrate and trichostatin A. (i) There was no correlation between cell death induction by butyrate or trichostatin A (TSA) and FR levels. (ii) Treatment with resveratrol or N-acetyl-l-cystein (NAC) of cells, in which the FR concentration was high, resulted in an almost complete reduction of FR levels. (iii) When, however, the cellular FR concentration was marginal, resveratrol caused a minor, and NAC a marked increase of FRs as well as of the extent of cell death. Thus, resveratrol and NAC acted as antioxidants only when the cellular FR levels were high, and acted as pro-oxidants when facing a low FR concentration. (iv) Since resveratrol and the antioxidant NAC exhibited analogous effects, it is concluded that the observed actions of resveratrol are due to polyphenolic redox reactions and not related to the stilbene moiety of the molecule. (v) The results indicate that the redox status of a given cell type plays an important role in determining whether resveratrol and other antioxidants promote cell death or protect cells from it.

Acetylcysteine↗