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PubMed2005

Polyphenols in cerebral ischemia: novel targets for neuroprotection.

Plant polyphenols are dietary components that exert a variety of biochemical and pharmacological effects. Recently, considerable interest has been focused on polyphenols because of their antioxidant, anti-inflammatory, and antiproliferative activities. Oxidative stress is thought to be a key event in the pathogenesis of cerebral ischemia. Overproduction of reactive oxygen species during ischemia/reperfusion could cause an imbalance between oxidative and antioxidative processes. Reactive oxygen species can damage lipids, proteins, and nucleic acids, thereby inducing apoptosis or necrosis. There is increasing evidence supporting the hypothesis that plant polyphenols can provide protection against neurodegenerative changes associated with cerebral ischemia. This article reviews the neuroprotective effects of plant extracts and their constituents that have been used in animal models of cerebral ischemia. The use of polyphenols as therapeutic agents in stroke has been suggested.

Animals↗
PubMed2005

Protective effects of tea polyphenols and caffeine.

Compounds derived from botanical sources, such as polyphenols from tea, have been of interest as possible therapeutic agents. Their benefits in terms of cancer chemoprevention have also been investigated primarily through in vitro and animal in vivo studies. Ultraviolet light from solar radiation has been proven to initiate and promote skin cancer, which is the most common malignancy in light-skinned populations. This review discusses the effects of tea polyphenols in preventing cutaneous carcinogenesis. Although many of the mechanisms and pathways discussed may be applicable to other carcinogens, this review focuses mainly on those related to ultraviolet light-induced processes and potential action sites for tea polyphenols. Since caffeine is a component of tea, and has also been suggested as a possible chemoprotective agent, it is included in this review. Based on data from numerous studies published in the scientific literature, tea polyphenols are promising chemopreventive agents against ultraviolet-induced skin cancers. Their antioxidant properties, inhibitory effects on signal transduction pathways, cell proliferation, angiogenesis and capacity for apoptosis induction, as well as possible immune protective effects, are among the mechanisms that contribute to skin cancer prevention.

Antioxidants↗
PubMed2005

Inhibitory effect(s) of polymeric black tea polyphenols on the formation of B(a)P-derived DNA adducts in mouse skin.

The biological activities and chemopreventive properties of green tea polyphenols have been demonstrated, while similar information regarding newly formed major polymeric polyphenols in black tea are not available. Cancer chemoprevention may be achieved by the inhibition of any stage of carcinogenesis. In the present study, we investigated the anti-initiating effects of five polymeric black tea polyphenol (PBP) fractions, by determining their effects on the formation of [3H]-B(a)P-derived DNA adducts as well as the activity of cytochrome P-450 isozymes CYP 1A1 and 1A2 in vitro employing rat liver microsomes. PBP 1-3 inhibited both the microsome catalyzed [3H]-B(a)P-derived DNA adduct formation as well as the activity of CYP 1A1 and 1A2 as assessed by the decreased formation of resorufin from the respective substrates. Further investigation revealed that topical pretreatment(s) of mice with PBP 1-5 (200 mug/day x 4) resulted in a significant decrease in the levels of single topical B(a)P (1 mg/mouse) - induced DNA adducts in epidermal DNA determined by employing 32P-post labeling analysis. Overall, our results suggest that black tea-derived PBPs have one of the chemopreventive properties shown by monomeric green tea polyphenols.

Animals↗
PubMed2000

Some polyphenols inhibit the formation of pentyl radical and octanoic acid radical in the reaction mixture of linoleic acid hydroperoxide with ferrous ions.

Effects of some polyphenols and their related compounds (chlorogenic acid, caffeic acid, quinic acid, ferulic acid, gallic acid, D-(+)-catechin, D-(-)-catechin, 4-hydroxy-3-methoxybenzoic acid, salicylic acid, L-dopa, dopamine, L-adrenaline, L-noradrenaline, o-dihydroxybenzene, m-dihydroxybenzene, and p-dihydroxybenzene) on the formation of 13-hydroperoxide octadecadienoic (13-HPODE) acid-derived radicals (pentyl radical and octanoic acid radical) were examined. The ESR spin trapping showed that chlorogenic acid, caffeic acid, gallic acid, D-(+)-catechin, D-(-)-catechin, L-dopa, dopamine, L-adrenaline, L-noradrenaline, and o-dihydroxybenzene inhibited the overall formation of 13-HPODE acid-derived radicals in the reaction mixture of 13-HPODE with ferrous ions. The ESR peak heights of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN)/13-HPODE-derived radical adducts decreased to 46+/-4% (chlorogenic acid), 54+/-2% (caffeic acid), 49+/-2% (gallic acid), 55+/-1% [D-(+)-catechin], 60+/-3% [D-(-)-catechin], 42+/-1% (L-dopa), 30+/-2% (dopamine), 49+/-2% (L-adrenaline), 24+/-2% (L-noradrenaline), and 54+/-5% (o-dihydroxybenzene) of the control, respectively. The high performance liquid chromatography-electron spin resonance (HPLC-ESR) and high performance liquid chromatography-electron spin resonance-mass spectrometries (HPLC-ESR-MS) showed that caffeic acid inhibited the formation of octanoic acid radical and pentyl radical to 42+/-2% and 52+/-7% of the control, respectively. On the other hand, the polyphenols and their related compounds had few inhibitory effects on the radical formation in the presence of EDTA. Visible absorbance measurement revealed that all the polyphenols exhibiting the inhibitory effect chelate ferrous ions. Above results indicated that the chelation of ferrous ion is essential to the inhibitory effects of the polyphenols.

Chromatography, High Pressure Liquid↗
PubMed2000

Protein-polyphenol interactions and in vivo digestibility of buckwheat groat proteins.

A rat model system, based on a diet with (Nb+) or without (Nb-) the inclusion of 0.7% of a 2:1 (w/w) mixture of Bacitracin and Neomycin sulfate (Nebacitin) was used to elucidate interactions of polyphenols with proteins in buckwheat. The treatment with the antibiotic Nebacitin suppresses the microflora in the large intestine and is used to obtain an estimate of the digestion occurring in the small intestine. Experimental buckwheat samples were obtained in order to contain different levels of polyphenol and were subjected to different hydrothermal treatments. It was found that a considerable interaction between polyphenols and proteins appeared during the hydrothermal treatment, and this interaction reduces the digestion of proteins through the small and large intestine. Microbial processes in the colon enhance the digestibility of protein, blocked by polyphenols in hydrothermally processed buckwheat.

Animals↗
PubMed2002

[The effect of an antioxidant tea polyphenols on cell apoptosis in rat model of cyclosporine-induced chronic nephrotoxicity].

OBJECTIVE: To investigate the effect of tea polyphenols on cell apoptosis in rat model of cyclosporine-induced chronic nephrotoxicity. METHODS: Four groups of animals in rat model of cyclosporine-induced chronic nephrotoxicity were respectively treated by olive oil (n = 6), tea polyphenols (TP, n = 6), cyclosporine A (CsA, n = 8) and TP plus CsA (n = 8). At the end of 28th day of treatment, all animals were sacrificed and blood was analyzed for blood serum creatinine and creatinine clearance, kidney tissue for pathologic analysis. The TUNEL assay, caspase-3 mRNA expression detected by reverse transcription-polymerase chain reaction (RT-PCR) and caspase-3 activity were used for the analysis of cell apoptosis. RESULTS: CsA plus TP ameliorated the CsA-induced decrease of renal function and interstitial fibrosis. There was a significant increase in the number of apoptosis-positive cells in the CsA-vs-CsA plus TP-treated group at four weeks (18.9 +/- 3.3 vs. 7.7 +/- 1.4, P < 0.05). The expression of caspase-3 mRNA and caspase-3 activity of CsA-treated group was significantly higher than that of CsA plus TP-treated group (P < 0.05). CONCLUSION: These results indicate that antioxidant tea polyphenols significantly inhibit apoptosis of tubular and interstitial cells in rat model of chronic cyclosporine-induced nephrotoxicity, and suggest that the decrease of cell apoptosis exerted by tea polyphenols may be one of mechanisms to protect renal function and tissue structure.

Animals↗
PubMedDate not supplied

Preclinical trial of the antitumoral therapeutic effectiveness of some natural polyphenolic biopreparations.

We have assessed the antitumoral action of the POLYAS I and POLYAS II vegetal polyphenolic biopreparations--separated and purified from Asclepias syriaca leaves - in rats with various experimental tumoral lines. We studied the therapeutic effect of different doses on the tumor generation process and compared it with the experimental oncostatic action of several standard chemotherapeutic drugs of clinical use (thiotepa, methotrexate, melphalan and cyclophosphamide). In our experimental treatment with the bioactive polyphenolic agents, we have used various doses, both higher and lower than the dose that had conditioned the expression of their antitumoral action upon Guerin T-8 lymphotropic epithelioma and upon Walker 256 carcinosarcoma. We found the antineoplastic effectiveness of those aromatic biopreparations from phytomass to be dose-dependent. We compared the evaluation indices of the antitumoral pharmacodynamic effect we obtained in the treatment with the POLYAS biopreparations with those of reference cytostatic agents. The antitumoral potential of the new natural biopreparations is higher than, equal or close to that of the standard oncochemotherapeutic agents. Antitumoral effectiveness can be improved by an experimental manipulation of the therapeutic doses--which proves the existence of a dose-response relationship. POLYAS I and POLYAS II polyphenolic biopreparations are compatible in point of effectiveness with the standard cytostatic agents, a fact that we considered relevant for the characterization of the POLYAS I and POLYAS II vegetal extracts as potential antineoplastic agents. The quantitative preclinical evaluation of the specific pharmacodynamic effect will be complemented by the investigation of the new polyphenolic biopreparations therapeutic effectiveness in tumors with various degrees of development.

Animals↗
PubMed2000

[Effects of tea polyphenols on cell kinetics and apoptosis of primary cultured rat skin keratinocytes].

In order to study the effects of tea polyphenols on cell growth and apoptosis of primary cultured rat skin keratinocytes, the safe dosage of tea polyphenols was determined by the release of lactate dehydrogenase(LDH). Cell counting(cytometry) and flow cytometry(FCM) were used to estimate the cell growth and the percentages of cells in different cell cycle phases or apoptosis. The results showed that tea polyphenols stimulated the cell growth from G1/G0 to G2/M phase, enhanced the synthesis of DNA(increase S phase) and increased the proliferative index(PI) from 18.17% to 25.62%. Also, it could block the occurrence of apoptosis. It is concluded that tea polyphenols could stimulate the growth of skin keratinocytes through stimulating the synthesis of cell DNA and inhibiting apoptosis.

Animals↗
PubMed2004

ROS-related enzyme expressions in endothelial cells regulated by tea polyphenols.

OBJECTIVE: Elevation of reactive oxygen species (ROS), especially the level of superoxide is a key event in many forms of cardiovascular diseases. To study the mechanism of tea polyphenols against cardiovascular diseases, we observed the expressions of ROS-related enzymes in endothelial cells. METHODS: Tea polyphenols were co-incubated with bovine carotid artery endothelial cells (BCAECs) in vitro and intracellular NADPH oxidase subunits p22phox and p67phox, SOD-1, and catalase protein were detected using Western blot method. RESULTS: Tea polyphenols of 0.4 microg/mL and 4.0 microg/mL (from either green tea or black tea) down-regulated NADPH oxidase p22phox and p67phox expressions in a dose-negative manner (P < 0.05), and up-regulated the expressions of catalase (P < 0.05). CONCLUSIONS: Tea polyphenols regulate the enzymes involved in ROS production and elimination in endothelial cells, and may be beneficial to the prevention of endothelial cell dysfunction and the development of cardiovascular diseases.

Animals↗
PubMed2004

[Isolation and structure identification of grape seed polyphenols and its effects on oxidative damage to cellular DNA].

AIM: To isolate polyphenols from grape seeds and to evaluate their antioxidant effects. METHODS: Pure compounds were isolated by using Diaion HP20, Toyopearl HW40 chromatography repeatedly, as well as semi-preparative RP-HPLC, from ethyl acetate extract of grape seeds. IR, MS, NMR, CD, X-Ray crystal diffraction spectral analysis were used to identify the structures. The antioxidant effects of different type of structures were screened by reducing power and DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) free radical scavenging tests. Then, SCGE (single cell gel-electrophoresis) technique was used to investigate the effects of these potent antioxidant phytochemicals on cellular DNA oxidative damage with mice spleen cells, damage was induced by H2O2. RESULTS: Eleven compounds were obtained including 3 novel structures, viniferones A, B and C. Proanthocyanidin B4, catecin, epicatechin and gallic acid showed strong antioxidant power, and at lower concentration (10 micromol x L(-1), 25 micromol x L(-1)), they can prevent cellular DNA damage, while 150 micromol x L(-1) catechin induced damage by itself. CONCLUSION: Viniferones A, B and C were reported for the first time. That polyphenols investigated were shown to be good cellular DNA oxidative damage-preventing phytochemicals at lower concentration, could be used to explain the nutrient effect of grape seed polyphenols at certain degree. At the same time, higher concentration of polyphenols can induce oxidative damage, suggesting that dose is one factor to determine the nutrient effects.

Animals↗
PubMed2005

[Near infrared determination of the content of caffeine in tea polyphenol].

In the present paper the caffeine in the tea polyphenol was analysed spectrally and quantitatively by using near infrared spectroscopy. From the original absorbance of caffeine in the tea polyphenol an obvious and strong peak can be viewed. By using second derivative, MSC (multiple scatter correction) and correlation analysis the spectral characteristics of caffeine in the near infrared region can be seen very clearly, thus the robust calibration model can be set up easily. The result obtained shows that through this technique the absorptive characteristic of those primary fundamentals of caffeine can be looked through easily, meanwhile, calibration test was performed to quantitatively measure the weight percent of caffeine in the tea polyphenol, and fine precision of the result was obtained in a comparatively very large range of concentration. The SEC(standard error of calibration) is 0.49%, and the correlation coefficient r is 0.993. The result shows that NIR is feasible and superior in analyzing the content of caffeine in tea polyphenol.

Caffeine↗
PubMed2001

Formation of novel bioactive metabolites from the reactions of pro-inflammatory oxidants with polyphenolics.

Dietary polyphenolics such as those in soy or red wine can have beneficial effects on the development of chronic human diseases. The mechanisms of action of isoflavones have been diverse and include their roles as weak estrogens, inhibitors of tyrosine kinase-dependent signal transduction processes and as antioxidants. Recent insights into the oxidative stress model of atherosclerosis suggest an interesting synthesis of these concepts. Sites of inflammation are associated with the formation of complex mixtures of reactive oxygen, nitrogen and halogenating species capable of modifying both endogenous biomolecules and polyphenolics. Of particular significance are the halogenation reactions mediated by myeloperoxidase that can modify key amino acids such as arginine and polyphenolics such as genistein. Hypochlorite, the reaction product of myeloperoxidase can halogenate polyphenolics to form stable derivatives with modified biological activity. Thus the in situ metabolism at sites of inflammation is unique and generates novel pharmacophores with potentially distinct modes of action from the parent compounds.

Flavonoids↗
PubMed2003

Optimization of catechol production by membrane-immobilized polyphenol oxidase: a modeling approach.

Although previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3-methylcatechol, 4-methylcatechol, catechol, and 4-chlorocatechol is demonstrated.

Catechol Oxidase↗
PubMed2002

Food-derived polyphenols inhibit pancreatic cancer growth through mitochondrial cytochrome C release and apoptosis.

There is increasing evidence that food-derived polyphenols have a beneficial effect for cancers. Our purpose was to determine the effect and mechanism of action of these compounds on pancreatic cancer. We measured effects of quercetin on pancreatic cancer in a nude mouse model. We also investigated the effects of quercetin, rutin, trans-resveratrol and genistein on apoptosis and underlying signaling in pancreatic carcinoma cells in vitro. Quercetin decreased primary tumor growth, increased apoptosis and prevented metastasis in a model of pancreatic cancer. In vitro quercetin and trans-resveratrol, but not rutin, markedly enhanced apoptosis, causing mitochondrial depolarization and cytochrome c release followed by caspase-3 activation. In addition, the effect of a combination of quercetin and trans-resveratrol on mitochondrial cytochrome c release and caspase-3 activity was greater than the expected additive response. The inhibition of mitochondrial permeability transition prevented cytochrome c release, caspase-3 activation and apoptosis caused by polyphenols. Nuclear factor-kappa B activity was inhibited by quercetin and trans-resveratrol, but not genistein, indicating that this transcription factor is not the only mediator of the polyphenols' effects on apoptosis. The results suggest that food-derived polyphenols inhibit pancreatic cancer growth and prevent metastasis by inducing mitochondrial dysfunction, resulting in cytochrome c release, caspase activation and apoptosis.

Animals↗
PubMed2004

Modulation of phosphatidylinositol-3-kinase/protein kinase B- and mitogen-activated protein kinase-pathways by tea polyphenols in human prostate cancer cells.

We have earlier shown that oral infusion of a polyphenolic fraction isolated from green tea, at a human achievable dose (equivalent to six cups of green tea per day), significantly inhibits prostate cancer (PCA) development and metastasis in transgenic adenocarcinoma of mouse prostate (TRAMP) model that closely mimics progressive form of human prostatic disease (Gupta et al. [2001]: Proc. Natl. Acad. Sci. U.S.A. 98:10350-10355.). A complete understanding of the mechanism(s) and molecular targets of PCA chemopreventive effects of tea polyphenols may be useful in developing novel approaches for its prevention. In this study, we employed two distinct human PCA cell lines viz. DU145 (androgen-unresponsive prostate carcinoma cells) and LNCaP (androgen-responsive prostate carcinoma cells) and, employing immunoblot analysis, we evaluated the effect of epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea and theaflavins (TF), the major polyphenol present in black tea on phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB) and mitogen-activated protein kinase (MAPK) pathways. Both EGCG and TF treatment were found to (i) decrease the levels of PI3K and phospho-Akt and (ii) increase Erk1/2 in both DU145 and LNCaP cells. Our data showing the inhibition of the constitutive levels of PI3K and the phosphorylation of Akt could be important because the treatment approaches should be aimed at the inhibition of the constitutive levels of PI3K and Akt. Our data also suggest that Erk1/2 could be involved in the anti-cancer effects of EGCG and TF. Taken together, our study, for the first time demonstrated the modulation of the constitutive activation of PI3K/Akt and Erk1/2 pathways by EGCG as well as TF. We suggest that detailed studies in appropriate tumor model system are needed to establish the relevance of the cell culture work to in vivo models.

Antineoplastic Agents↗
PubMed1995

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)

Animals↗
PubMed2000

Cell cycle dysregulation by green tea polyphenol epigallocatechin-3-gallate.

Epidemiological, in vitro cell culture, and in vivo animal studies have shown that green tea or its constituent polyphenols, particularly its major polyphenol epigallocatechin-3-gallate (EGCG) may protect against many cancer types. In earlier studies, we showed that green tea polyphenol EGCG causes a G0/G1-phase cell cycle arrest and apoptosis of human epidermoid carcinoma (A431) cells. We also demonstrated that these effects of EGCG may be mediated through the inhibition of nuclear factor kappa B that has been associated with cell cycle regulation and cancer. In this study, employing A431 cells, we provide evidence for the involvement of cyclin kinase inhibitor (cki)-cyclin-cyclin-dependent kinase (cdk) machinery during cell cycle deregulation by EGCG. As shown by immunoblot analysis, EGCG treatment of the cells resulted in significant dose- and time-dependent (i) upregulation of the protein expression of WAF1/p21, KIP1/p27, p16 and p18, (ii) downmodulation of the protein expression of cyclin D1, cdk4 and cdk6, but not of cyclin E and cdk2, (iii) inhibition of the kinase activities associated with cyclin E, cyclin D1, cdk2, cdk4 and cdk6. Taken together, our study suggests that EGCG causes an induction of G1-phase ckis, which inhibit the cyclin-cdk complexes operative in G0/G1 phase of the cell cycle thereby causing a G0/G1-phase arrest of the cell cycle, which is an irreversible process ultimately resulting in an apoptotic cell death. We suggest that the naturally occurring agents such as green tea polyphenols which may inhibit cell cycle progression could be developed as potent anticancer agents for the management of cancer.

Apoptosis↗
PubMed1986

The inhibition of digestive enzymes by polyphenolic compounds.

The ability of polyphenolic compounds to form insoluble complexes with other macro-molecules such as proteins has long been associated with the observed reduction in nutritive value resulting from their inclusion in animal diets. Naturally occurring polyphenols, and in particular condensed tannins isolated from various plant sources, have been shown to inhibit in vitro a number of digestive enzymes including trypsin, alpha-amylase and lipase. In addition, the results of various feeding trials suggest that similar reductions in intestinal digestive enzyme activity may result from the feeding of high polyphenolic diets. The evidence for this is summarised and discussed in relation to the possible effect of enzyme inhibition on reduced nutritive value and it is concluded that the observed reduction in protein availability found in vivo on consuming high tannin diets cannot simply be explained by the formation of dietary protein tannin complexes and that the ability of polyphenolic compounds to inhibit digestive enzymes may be of greater significance than realised previously.

Animals↗