SEARCH · Search PubMed

Results for “Polyphenols”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed2000

Naturally occurring polyphenolic antioxidants modulate IgE-mediated mast cell activation.

Reactive oxygen species (ROS) are known to modulate activities of a host of kinases, phosphatases and transcription factors. Rutin and chlorogenic acid (CGA) are the major polyphenolic antioxidants present in the small molecular fraction of smokeless tobacco leaf extracts, as ascertained by reverse-phase high-pressure liquid chromatography (HPLC) and mass spectrometry. Levels of intracellular ROS in resting versus antigen-immunoglobulin E (IgE)-challenged murine mast cells were measured at 510 nm by fluorescence-activated cell sorting (FACS) using carboxy-dichlorofluorescein (DCFH-DA). Enhanced ROS production was observed in IgE-sensitized mast cells following antigenic challenge. Rutin and CGA reduced ROS levels in antigen-IgE-activated mast cells. Concomitantly, they also profoundly inhibited histamine release by these activated mast cells. In contrast, rutin and CGA augmented the inducible cytokine messages, i.e. interleukin (IL)-10, IL-13, interferon-gamma (IFN-gamma), IL-6 and tumour necrosis factor-alpha (TNF-alpha) in IgE-sensitized mast cells following antigen challenge. This study indicates that tobacco polyphenolic antioxidants that quench intracellular ROS, differentially affect two effector functions of antigen-IgE-activated mast cells. This model system may be employed to determine the molecular target of polyphenols. The potential role of these polyphenolic antioxidants on IgE-mediated allergy in vivo depends on a balance of their differential effects on mast cell activation.

Animals↗

PubMed1999

Analysis of tea polyphenols.

Tea is the most highly consumed beverage in the world, other than water. However, unlike water, tea contains substantial amounts of polyphenols that have unique biological activities and may be responsible for many of the health benefits of tea. As a result, it is essential to be able to measure the various tea-associated polyphenols. Total polyphenol content is currently measured by using methodology based on reducing activity. Several HPLC systems with detectors that, collectively, have wide ranges in sensitivity have been developed for analysis of individual flavonoids in tea and biological samples, and for theaflavins in tea. Catechins also have been measured in plasma by solid phase extraction, addition of a chromophore, and colorimetric quantification. Except for theaflavins in tea, routine and robust methods for the measurement of polyphenol condensation products (dimers and thearubigens) in tea and biological samples have not been developed. Although in vitro and animal studies suggest substantial metabolism of flavonoids in the gastrointestinal tract, only a single HPLC procedure has been assembled for monitoring the metabolic products of quercetin in urine of human subjects.

Animals↗

PubMed2001

Ester bond-containing tea polyphenols potently inhibit proteasome activity in vitro and in vivo.

It has been discovered that proteasome inhibitors are able to induce tumor growth arrest or cell death and that tea consumption is correlated with cancer prevention. Here, we show that ester bond-containing tea polyphenols, such as (-)-epigallocatechin-3-gallate (EGCG), potently and specifically inhibit the chymotrypsin-like activity of the proteasome in vitro (IC(50) = 86-194 nm) and in vivo (1-10 microm) at the concentrations found in the serum of green tea drinkers. Atomic orbital energy analyses and high performance liquid chromatography suggest that the carbon of the polyphenol ester bond is essential for targeting, thereby inhibiting the proteasome in cancer cells. This inhibition of the proteasome by EGCG in several tumor and transformed cell lines results in the accumulation of two natural proteasome substrates, p27(Kip1) and IkappaB-alpha, an inhibitor of transcription factor NF-kappaB, followed by growth arrest in the G(1) phase of the cell cycle. Furthermore, compared with their simian virus-transformed counterpart, the parental normal human fibroblasts were much more resistant to EGCG-induced p27(Kip1) protein accumulation and G(1) arrest. Our study suggests that the proteasome is a cancer-related molecular target of tea polyphenols and that inhibition of the proteasome activity by ester bond-containing polyphenols may contribute to the cancer-preventative effect of tea.

Calpain↗

PubMed1984

Relationship between polyphenol intake and blood glucose response of normal and diabetic individuals.

Five leguminous and eight nonleguminous foods were analyzed for polyphenol concentration by the Prussian Blue and the Folin Denis methods and correlated with blood glucose response (glycemic index) in normal or diabetic volunteers. Polyphenol concentrations and intakes per 50 g available carbohydrate portions were higher in the leguminous foods than those in the nonleguminous foods. In both normal and diabetic individuals, a negative correlation was observed between glycemic index and the concentration or total intake of polyphenols. Polyphenols, especially the large polymeric type or condensed tannins, appear to be responsible in part for the reduced glycemic response to carbohydrate foods and in part to lower blood glucose response to legumes compared with cereal products.

Blood Glucose↗

PubMed2000

Tea polyphenols: prevention of cancer and optimizing health.

The tea plant Camellia sinesis is cultivated in >30 countries. Epidemiologic observations and laboratory studies have indicated that polyphenolic compounds present in tea may reduce the risk of a variety of illnesses, including cancer and coronary heart disease. Most studies involved green tea, however; only a few evaluated black tea. Results from studies in rats, mice, and hamsters showed that tea consumption protects against lung, forestomach, esophagus, duodenum, pancreas, liver, breast, colon, and skin cancers induced by chemical carcinogens. Other studies showed the preventive effect of green tea consumption against atherosclerosis and coronary heart disease, high blood cholesterol concentrations, and high blood pressure. Because the epidemiologic studies and research findings in laboratory animals have shown the chemopreventive potential of tea polyphenols in cancer, the usefulness of tea polyphenols for humans should be evaluated in clinical trials. One such phase 1 clinical trial is currently under way at the MD Anderson Cancer Center in collaboration with Memorial Sloan-Kettering Cancer Center. This study will examine the safety and possible efficacy of consuming the equivalent of > or =10 cups (> or =2.4 L) of green tea per day. The usefulness of tea polyphenols may be extended by combining them with other consumer products such as food items and vitamin supplements. This "designer-item" approach may be useful for human populations, but it requires further study.

Animals↗

PubMed1992

Inhibitory effect of topical application of a green tea polyphenol fraction on tumor initiation and promotion in mouse skin.

A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1995

Cloning and characterization of polyphenol oxidase cDNAs of Phytolacca americana.

Two cDNA clones encoding polyphenol oxidases were isolated from a cDNA library constructed from a log-phase suspension culture of Phytolacca americana (pokeweed) producing betalains. The clones exhibit 93 and 86% sequence identity at the nucleotide and deduced amino acid levels, respectively. Both clones contain two copper-binding domains characterized by histidine-rich regions, which are found ubiquitously in all polyphenol oxidases/tyrosinases, and a putative third histidine-rich, copper-binding region, which is common to all plant polyphenol oxidases. One of the Phytolacca cDNA deduced amino acid sequences contains the ubiquitous transit peptide for all proteins targeted to the internal lumen of thylakoid membranes of plastids and is considered to be 98 residues in length based on a proposed sequence cleavage site motif. This would produce a processed peptide of approximately 54 kD. In addition to common features of transit peptides, it was found that an additional conserved region for polyphenol oxidases was located between the hydroxy amino acid-rich region and the thylakoid transfer domain. Spatial and temporal expression was investigated by northern blot analysis of total RNA from various organs of Phytolacca plants. Transcripts of the two clones were found to be 2.1 and 2.3 kb, respectively. Both transcripts were present only at substantial levels in ripening, betalain-containing fruit.

Amino Acid Sequence↗

PubMed1981

Spinach Thylakoid Polyphenol Oxidase : ISOLATION, ACTIVATION, AND PROPERTIES OF THE NATIVE CHLOROPLAST ENZYME.

Polyphenol oxidase activity (E.C. 1.14.18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. The higher molecular weight enzyme is the predominant form in freshly isolated preparations but on aging or further purification, the amount of lower molecular weight enzyme increases at the expense of the higher.Sonication releases polyphenol oxidase from the membrane largely in the latent state. C(18) fatty acids, especially linolenic acid, are potent activators of the enzymic activity. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time.Purified polyphenol oxidase utilizes o-diphenols as substrates and shows no detectable levels of monophenol or p-diphenol oxidase activities. The K(m) values for 3,4-dihydroxyphenylalanine and O(2) are 6.5 and 0.065 millimolar, respectively. Suitable substrates include chlorogenic acid, catechol, caffeic acid, pyrogallol, and dopamine; however, the enzyme is substrate-inhibited by the last four at concentrations near their K(m) A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present.

Journal Article↗

PubMed2002

Inhibition by apple polyphenols of ADP-ribosyltransferase activity of cholera toxin and toxin-induced fluid accumulation in mice.

The effects of crude polyphenol extracted from immature apples on the enzymatic and biological activities of a cholera toxin (CT) were investigated. When the apple polyphenol extract (APE) was examined for properties to inhibit CT-catalyzed ADP-ribosylation of agmatine, it was found that APE inhibited it in a dose-dependent manner. The concentration of APE to inhibit 50% of the enzymatic activity of CT (15 microg/ml) was approximately 8.7 microg/ml. The APE also diminished CT-induced fluid accumulation in two diarrhea models for in vivo mice. In the ligated ileum loops, 25 microg of APE significantly inhibited fluid accumulation induced by 500 ng of CT. In a sealed mouse model, even when APE was administered orally 10 min after a toxin injection, fluid accumulation was significantly inhibited at a comparable dosage. Lineweaver-Burk analysis demonstrated that APE had negative allosteric effects on CT-catalyzed NAD: agmatine ADP-ribosyltransferase. We fractionated the APE into four fractions using LH-20 Sephadex resin. One of the fractions, FAP (fraction from apple polyphenol) 1, which contains non-catechin polyphenols, did not significantly inhibit the CT-catalyzed ADP-ribosylation of agmatine. FAP2, which contains compounds with monomeric, dimeric, and trimeric catechins, inhibited the ADP-ribosylation only partially, but significantly. FAP3 and FAP4, which consist of highly polymerized catechin compounds, strongly inhibited the ADP-ribosylation, indicating that the polymerized structure of catechin is responsible for the inhibitory effect that resides in APE. The results suggest that polymerized catechin compounds in APE inhibit the biological and enzymatic activities of CT and can be used in a precautionary and therapeutic manner in the treatment of cholera patients.

ADP Ribose Transferases↗

PubMedDate not supplied

Antibacterial activity of polyphenol components in oolong tea extract against Streptococcus mutans.

The purpose of the present study was to determine the antibacterial activity of oolong tea extract on oral streptococci, including Streptococcus mutans and Streptococcus sobrinus, and to identify the response to its components. Antibacterial activity was found when the extract was added to S. mutans cells in chemically defined medium but not in complex broth media. Further, pretreatment with bovine serum albumin reduced the antibacterial activity. The extract showed antibacterial activity against all of the oral streptococci examined, with the highest activity against S. mutans MT8148R. This activity was found to originate from a monomeric polyphenol-rich fraction, and it was stronger than that of pure polyphenols. Moreover, some combinations of monomeric polyphenols showed the highest level of antibacterial activity. These results suggest that the antibacterial activity of oolong tea extract is caused by a synergistic effect of monomeric polyphenols, which can easily bind to proteins.

Animals↗

PubMed2000

Analyses of polyphenols in cacao liquor, cocoa, and chocolate by normal-phase and reversed-phase HPLC.

The antioxidant polyphenols in cacao liquor, a major ingredient of chocolate and cocoa, have been characterized as flavan-3-ols and proanthocyanidin oligomers. In this study, various cacao products were analyzed by normal-phase HPLC, and the profiles and quantities of the polyphenols present, grouped by molecular size (monomers to approximately oligomers), were compared. Individual cacao polyphenols, flavan-3-ols (catechin and epicatechin), and dimeric (procyanidin B2), trimeric (procyanidin C1), and tetrameric (cinnamtannin A2) proanthocyanidins, and galactopyranosyl-ent-(-)-epicatechin (2alpha-->7, 4alpha-->8)-(-)-epicatechin (Gal-EC-EC), were analyzed by reversed-phase HPLC and/or HPLC/MS. The profile of monomers (catechins) and proanthocyanidin in dark chocolate was similar to that of cacao liquor, while the ratio of flavan-3-ols to the total amount of monomeric and oligomeric polyphenols in the case of pure cocoa powder was higher than that in the case of cacao liquor or chocolate.

Anthocyanins↗

PubMed2001

Green tea polyphenol epigallocatechin inhibits DNA replication and consequently induces leukemia cell apoptosis.

Consistent with the putative role of green tea in cancer prevention, tea polyphenols have previously been shown to inhibit tumor cell proliferation by inducing G1 or G2/M cell cycle arrests, also documented is their ability to induce apoptosis (programmed cell death). However, it is unclear whether or not the cell cycle effects of polyphenols are related to their cell death-inducing ability. Here we report that the tea polyphenol (-)-epigallocatechin (EGC) inhibits DNA replication in three leukemia cancer cell lines, Jurkat T, HL-60 and K562. Among all the tested tea polyphenols, EGC was found to be the most potent in accumulation of S phase cells and inhibition of the S-G2 progression. In addition, EGC-mediated inhibition of S phase progression results in induction of apoptosis, as determined by sub-G1 cell population, breakage of endonuclear DNA, cleavage of poly(ADP-ribose) polymerase and loss of cell viability. When used in cells containing low S and high G1 and G2/M populations, EGC did not induce apoptosis. Furthermore, EGC did not inhibit M-G1 transition. Our finding that EGC inhibits S phase progression that results in leukemia cell death provides a novel and plausible molecular mechanism for how green tea may inhibit the growth of rapidly proliferating neoplastic cells.

Apoptosis↗

PubMed2001

The green tea polyphenol (-)-epigallocatechin-3-gallate blocks nuclear factor-kappa B activation by inhibiting I kappa B kinase activity in the intestinal epithelial cell line IEC-6.

The I kappa B kinase complex (IKK) mediates activation of the transcription factor nuclear factor-kappa B (NF-kappa B). We previously showed that green tea polyphenols inhibited endotoxin-mediated tumor necrosis factor-alpha (TNF alpha) production by blocking NF-kappa B activation. In this study, we evaluated whether green tea polyphenols inhibit NF-kappa B by blocking IKK activity. We assessed IKK activity by detecting changes in phosphorylation of an I kappa B alpha-glutathione S-transferase (GST) fusion protein. IEC-6 cells pretreated with an extract of green tea polyphenols (GrTPs; 0--0.4 mg/ml) had diminished TNF alpha-induced IKK and NF-kappa B activity. Of the various GrTPs, (-)-epigallocatechin-3-gallate (EGCG) was the most potent inhibitor. We next examined whether EGCG inhibited activated IKK. In cytosolic extracts of TNF alpha-stimulated cells, EGCG inhibited phosphorylation of I kappa B alpha-GST (IC(50) > 18 microM) consistent with inhibition of IKK activity. Using other polyphenols, we showed that the gallate group was essential for inhibition, and antioxidants were ineffective in blocking activated IKK. Importantly, EGCG decreased IKK activity in cytosolic extracts of NIK transiently transfected cells. This latter finding showed that our findings were not related to nonspecific kinase activity. In conclusion, EGCG is an effective inhibitor of IKK activity. This may explain, at least in part, some of the reported anti-inflammatory and anticancer effects of green tea.

Animals↗

PubMedDate not supplied

Chemopreventive effects of green tea polyphenols correlate with reversible induction of p57 expression.

Green tea polyphenols are known to induce apoptosis in certain types of tumor cells. However, the mechanism(s) that enables normal cells to evade the apoptotic effect is still not understood. In this study, Western blot analysis combined with cycloheximide treatment was used to examine the effects of green tea polyphenols on the expression levels of p57, a cyclin-dependent kinase and apoptosis inhibitor, in normal human keratinocytes and in the oral carcinoma cell lines SCC25 and OSC2. The results showed that the most potent green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), induced p57 in normal keratinocytes in a dosage- and time-dependent manner, while the levels of p57 protein in oral carcinoma cells were unaltered. The differential response in p57 induction was consistent with the apoptosis status detected by annexin V assay. The data suggest that the chemopreventive effects of green tea polyphenols may involve p57-mediated cell cycle regulation in normal epithelial cells.

Aged↗

PubMed2002

Effects of red wine polyphenolic compounds on the cardiovascular system.

Phenolic phytochemicals are widely distributed in the plant kingdom. Regarding the protective effects on organisms, the polyphenol group is the most important. In different experiments, it has been shown that selected polyphenols, mainly flavonoids, possess protective effects on the cardiovascular system, as well as anticancer, antiviral and antiallergic properties. In coronary heart disease, the protective effects include mainly antithrombic, antioxidant, anti-ischaemic and vasorelaxant properties of flavonoids. It has been hypothesised that the phenomenon of a low incidence of coronary heart disease in French people may be partially related to the pharmacological properties of polyphenolic compounds included in red wine. Many epidemiological studies have shown that regular flavonoid intake is associated with reduced risk of cardiovascular diseases. This review article discusses the chemical structure of polyphenols and their beneficial properties in the cardiovascular system. (Fig. 1, Ref 74.).

Animals↗

PubMed2001

Cancer Chemoprevention: Tea Polyphenol Induced Cellular and Molecular Responses.

Considerable evidence is now available showing that tea infusions can prevent tumor induction in experimental animals by a variety of chemical carcinogens. Such an action is mainly attributed to the polyphenolic constituets of tea. These polyphenols possess antioxidant activity and interfere with carcinogen activation, show anti-mutagenic and anti-genotoxic properties, exhibit anti-tumor promoting activity and alter certain events in signal transduction pathways. Tea polyphenols are known to exhibit cytotoxicity towards various human tumor cell lines as well as growth inhibition that is accompanied by cell cycle arrest. It has been demonstrated that the cytotoxicity result in inducton of apoptosis. Additionally, tea polyphenols are good candidates for sensitizing tumor cells leading to apoptotic death by cytotoxic drugs.

Journal Article↗

PubMed1995

[Inhibitory effect of green tea polyphenols varnish on oral main cariogenic bacteria.].

This study observed the bacteriostatic effect of green tea polyphenols varnish,found green tea polyphenols varnish had significant inhibitory action on Streptococcus mutans,Streptococcus sobrinus and Lactobacilli.growth test showed the growth inhibitory rate of S.mutans and S.sobrinus was positive proportion with the concentration of green tea polyphenols varnish,demonstrated green tea polyphenols varnish possess certain anticariogenic effect.

English Abstract↗

PubMed1996

[The role of dietary plant polyphenols in health maintenance].

Plant polyphenols are typical representatives of natural substances in foods of plant origin, in particular in fruit, tea and vegetables. They display multiple structure-conditioned interactions with various biomolecules. Their general property is the antioxidant and chelating effect and modulation of activity of various enzyme systems. In the diet they act mostly as health promoting factors during various chemical and physical stresses of the organism. They are antiatherogenic and anticarcinogenic, on the principle of inhibition of oxidative destruction of various oxylabel biological structures, inhibition of processes of bioactivation of carcinogens, blocking LDL oxidation and stimulating the activity of antioxidant and detoxication enzymes. Some of them have mutagenic properties in genotoxicity tests (quercetin, colours of red wine, phenolic acids of coffee), however, the results of animal experiments and epidemiological studies do not confirm the risk of neoplastic disease in subjects with a normal intake of these substances. The biological activity of plant polyphenols is part of the activity of other chemopreventive dietary constituents and essential nutrients. In this complex polyphenols act in many ways on the principle of synergism. The use of the health promoting properties of polyphenols isolate from plants and their administration in a pure state is not foreseen. However, under conditions it is desirable to increase the consumption of foods which are important sources of these substances.

Humans↗