Effects Of Tea Polyphenols Research Articles

Comparative evaluation of green and black tea consumption on the iron status of omnivorous and vegetarian people

The effect of tea polyphenols on the bioavailability of iron and the iron status of man is controversially discussed. Especially women prior to menopause are a vulnerable group regarding their iron status, with a vegetarian diet increasing this risk. This study aimed to determine several iron status parameters for men and women consuming a mixed diet or being vegetarians and drinking tea. In a cross-over study, the effect of tea consumption on the iron status of healthy male and female omnivorous compared to vegetarian volunteers was tested. All volunteers consumed either green tea or black tea (each 1L/d) for four weeks together with meals or avoided tea for four weeks (cross-over design). Blood samples were withdrawn prior to the one week depletion period, at the start of the intervention phase and thereafter weekly during intervention. The iron status parameters hemoglobin, hematocrit, transferrin, total iron and iron binding capacity were not affected by the consumption of tea. In contrast, plasma ferritin values were significantly reduced after tea consumption, especially in those women with basal ferritin values lower than 25μg/L, already after two weeks of intervention with tea (1L/d).

ATP-dependent potassium channels and mitochondrial permeability transition pores play roles in the cardioprotection of theaflavin in young rat

Previous studies have confirmed that tea polyphenols possess a broad spectrum of biological functions such as anti-oxidative, anti-bacterial, anti-tumor, anti-inflammatory, anti-viral and cardiovascular protection activities, as well as anti-cerebral ischemia-reperfusion injury properties. But the effect of tea polyphenols on ischemia/reperfusion heart has not been well elucidated. The aim of this study was to investigate the protective effect of theaflavin (TF1) and its underlying mechanism. Young male Sprague-Dawley (SD) rats were randomly divided into five groups: (1) the control group; (2) TF1 group; (3) glibenclamide + TF1 group; (4) 5-hydroxydecanoate (5-HD) + TF1 group; and (5) atractyloside + TF1 group. The Langendorff technique was used to record cardiac function in isolated rat heart before and after 30 min of global ischemia followed by 60 min of reperfusion. The parameters of cardiac function, including left ventricular developing pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal differentials of LVDP (± LVdP/dt (max)) and coronary flow (CF), were measured. The results showed: (1) compared with the control group, TF1 (10, 20, 40 μmol/l) displayed a better recovery of cardiac function after ischemia/reperfusion in a concentration-dependent manner. At 60 min of reperfusion, LVDP, ± LVdP/dt (max) and CF in the TF1 group were much higher than those in the control group, whereas left ventricular end-diastolic pressure (LVEDP) in the TF1 group was lower than that in the control group (P < 0.01). (2) Pretreatment with glibenclamide (10 μmol/l), a K(ATP) antagonist, completely abolished the cardioprotective effects of TF1 (20 μmol/l). Also, most of the effects of TF1 (20 μmol/l) on cardiac function after 60 min of reperfusion were reversed by 5-HD (100 μmol/l), a selective mitochondria K(ATP) antagonist. (3) Atractyloside (20 μmol/l), a mitochondrial permeability transition pore (mPTP) opener, administered at the beginning of 15 min of reperfusion completely abolished the cardioprotection of TF1 (20 μmol/l). The results indicate that TF1 protects the rat heart against ischemia/reperfusion injury through the opening of K(ATP) channels, particularly on the mitochondrial membrane, and inhibits mPTP opening.

Effect of Green Tea Catechins on the Postprandial Glycemic Response to Starches Differing in Amylose Content

The effect of tea polyphenols (TPLs), specifically tea catechins, on the postprandial glycemic response to cooked starches differing in amylose contents was investigated. The in vivo test using a mouse model showed a moderate reduction of the postprandial glycemic response to co-cooked normal (containing 27.8% amylose) or waxy corn starch with 10% TPLs (dry weight of starch), while an augmented glycemic response with a delayed blood glucose peak was observed when high amylose corn starch (HAC, containing 79.4% amylose) was used as the starch component. Enzyme kinetics results demonstrated that TPLs noncompetitively inhibit the digestion of waxy or normal corn starch, while the digestion rate of HAC starch was increased in the presence of TPLs, which supports the observed postprandial glycemic responses. Further studies using X-ray powder diffraction showed that the diffraction intensity (area under the diffraction curves) of normal and HAC starch was increased by 45% and 74%, respectively, whereas no change was observed for waxy corn starch. Consistently, dynamic laser light scattering studies using a solution of pure amylose showed an increased hydrodynamic radius of amylose molecules from ∼54 nm to ∼112 nm in the presence of TPLs. These experimental results indicate that there might exist an interaction between TPLs and amylose, which facilitates the association of amylose molecules to form a special nonordered structure that can produce a high and sustained postprandial glycemic response. Thus, a combination of tea polyphenols and specific starches could be used to manipulate postprandial glycemic response for glycemic control and optimal health.

Effect of tea polyphenols on microbiological and biochemical quality of Collichthys fish ball

Tea polyphenols (TP), as the most active constituents of tea, are considered natural food additives. This study examined the preservative properties of TP for Collichthys fish ball in well storage. Vacuum-packed Collichthys fish balls were treated with 0, 0.1, 0.15, 0.20, 0.25, and 0.30 g kg(-1) TP and stored at 0 °C for 17 days. Microbiological results were obtained using a biochemical test, API system kit, and 16S rDNA sequence analysis. Results confirmed that the dominant bacteria in Collichthys fish balls are the genera Serratia and Pseudomonas. Total viable counts dropped two orders of magnitude in Collichthys fish balls with 0.25 g kg(-1) TP compared with the control. The advantages of total volatile basic nitrogen value, 2-thiobarbituric acid value and texture value were clearly observed, whereas pH and whiteness value exhibited no significant decrease for the group treated with 0.25 g kg(-1) TP. More than 0.25 g kg(-1) TP added could retain excellent fish ball characteristics in terms of sensory assessment after 17 days. The shelf life of Collichthys fish balls supplemented with tea polyphenols can be prolonged for an additional 6 days in good condition at 0 °C storage.

Abstract B68: EGCG and theaflavin are direct inhibitors of the oncogenic lipid kinase, sphingosine kinase 1

Abstract Epigallocatechin-3-gallate (EGCG) and theaflavin are polyphenols from green and black tea, respectively, that have been shown to have anti-cancer/anti-inflammatory effects through their antioxidant properties. Recent studies indicate that these tea polyphenols may also target the sphingosine kinase (SphK)/sphingosine-1-phosphate (S1P) signaling pathway. Therefore we examined whether these tea polyphenols can directly inhibit SphK1 catalytic activity. To accomplish this, we performed in vitro SphK activity assays to determine the kinetics properties of EGCG and theaflavin toward SphK1. These analyses indicate that EGCG, and its related tea polyphenols theaflavin, GCG and catechin all directly inhibit SphK1 catalytic activity. Further kinetic analysis indicates that EGCG is a non-competitive inhibitor of SphK1 (Ki = 450-500 nM). These data are the first demonstration of a direct inhibitory effect of tea polyphenols on SphK1 catalytic activity. Importantly, given the oncogenic role of SphK1, they suggest that SphK1 is a target of the anti-cancer/anti-inflammatory actions of the tea polyphenols such as EGCG and theaflavin. They further suggest that inhibiting SphK1 activity, using tea polyphenols, can be an effective chemopreventative strategy and that the structures of these polyphenols could serve as novel molecular scaffolds for the development of SphK inhibitors. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B68.

The protective effects of tea polyphenols on the function of organs

Tea is widely accepted as a beverage all over the world, and as the technology developed, various studies have clearly demonstrated tea polyphenols possess potent neuroprotective effect. This effect has been attributed to their potent antioxidan, free radical scavenging, anti -inflammatory, regulating signal pathway actions, ect.. This article reviews the protective effects of tea polyphenols on the function of organs from these aspects; provides theoretical basis for clinical use,fundamental research and development of tea polyphenols' new products. Key words: Tea polyphenols; Ischemia/reperfusion; Brain protection

Effect of dietary tea polyphenols on growth performance and cell-mediated immune response of post-weaning piglets under oxidative stress

To gain insights into the effects of tea polyphenols (TP) on growth performance and cell-mediated immune response of piglets under oxidative stress, an oxidative stress model was established by intraperitoneally injecting weaned piglets with diquat. After intake of either basal diet or TP-supplemented diet for 7 d, half of the piglets in each group were challenged with diquat. Results showed that dietary TP alleviated growth depression to some extent. A T lymphocyte transformation test (LTT) demonstrated that TP promoted the proliferation and activation of T lymphocytes. The ratio of CD4+/CD8+ was elevated, indicating a recovering tendency from immune damages caused by oxidative stress. The increment of pro-inflammatory IL-1 caused by oxidative stress was attenuated, and the concentration of serum IFN-γ was decreased by TP-supplementation. However, the serum concentrations of anti-inflammatory cytokine, such as IL-4, were greatly enhanced by TP, which suggested an immune shift from Th1 to Th2. These findings supported the immunomodulatory potential of TP for piglets subjected to oxidative stress.

The effects of tea polyphenols onCandida albicans: inhibition of biofilm formation and proteasome inactivation

The adherence of Candida albicans to one another and to various host and biomaterial surfaces is an important prerequisite for the colonization and pathogenesis of this organism. Cells in established biofilms exhibit different phenotypic traits and are inordinately resistant to antimicrobial agents. Recent studies have shown that black and green tea polyphenols exhibit both antimicrobial and strong cancer-preventive properties. Experiments were conducted to determine the effects of these polyphenols on C. albicans. Standard growth curves demonstrated a 40% reduction in the growth rate constant (K) with a 2 mg/mL concentration of Polyphenon 60, a green tea extract containing a mixture of polyphenolic compounds. Cultures treated with 1.0 micromol/L -(-)epigallocatechin-3-gallate (EGCG), the most abundant polyphenol, displayed a 75% reduction of viable cells during biofilm formation. Established biofilms treated with EGCG were also reduced, by 80%, as determined through XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) colorimetric assays. Identical concentrations of epigallocatechin and epicatechin-3-gallate demonstrated similar biofilm inhibition. Further investigations regarding the possible mechanism of polyphenol action indicate that in vivo proteasome activity was significantly decreased when catechin-treated yeast cells were incubated with a fluorogenic peptide substrate that measured proteasomal chymotrypsin-like and peptidyl-glutamyl peptide-hydrolyzing activities. Impairment of proteasomal activity by tea polyphenols contributes to cellular metabolic and structural disruptions that expedite the inhibition of biofilm formation and maintenance by C. albicans.

Effects of tea polyphenols on freshness-keeping of partial-frozen silver carp in cold storage.

Effects of tea polyphenols on freshness-keeping of partial-frozen silver carp in cold storage.

Effect of tea polyphenols on the retrogradation of rice starch

The effect of tea polyphenols (TPLs) on the retrogradation of rice starch (RS) was investigated. TPLs-fortified RS exhibited retarding of retrogradation as assessed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The analytic samples had a water–RS/TPLs ratio of 2:1. RS/TPLs mixing ratios were 5/0, 5/0.3, 5/0.5, 5/0.7, and 5/1 (w/w) that equated with RS containing 0%, 6%, 10%, 14%, and 20% TPLs (based on RS weight), respectively. In the DSC analysis, the temperature and enthalpy of starch gelatinization obviously decreased as the polyphenols level increased. After storage at 4 °C, retrogradation enthalpy for RS with 10%, 14%, and 20% TPLs did not appear until storage of 20 days. After 10 days of storage at 4 °C, RS gel with 10%, 14%, or 20% TPLs had almost no recrystallization of the retrogradation. The overall results demonstrate that the marked inhibitory effect of TPLs on the retrogradation of RS.

In Vitro Effects of Tea Polyphenols on Redox Metabolism, Oxidative Stress, and Apoptosis in PC12 Cells

Tea polyphenols, especially catechins, have been reported to be potent antioxidants and beneficial in oxidative stress-related diseases including cancer. Numerous animal and cell culture models demonstrate anticancer effects of tea catechins. Experimental and epidemiological evidence suggests the use of black tea polyphenols (BTP), green tea catechins (especially epigallocatechin gallate [EGCG]), and other polyphenols in preventing the progression of cancer both in animal and human populations. In the present study, we have demonstrated alterations in oxidative stress and redox metabolism using an isolated cell-free system and also in PC12 cancer cells after treatment with EGCG and BTP. We have demonstrated that tea catechins, alter the production of reactive oxygen species, glutathione metabolism, lipid peroxidation, and protein oxidation under in vitro conditions. We have also demonstrated that EGCG and BTP affect redox metabolism under cell culture conditions. Induction of apoptosis was observed, after the treatment with tea polyphenols, as shown by increased DNA breakdown and activation of the apoptotic markers, cytochrome c, caspase 3, and poly-(ADP-ribose) polymerase. These results may have implications in determining the chemopreventive and therapeutic use of tea catechins in vivo.

Effect of tea polyphenols on TNF-α and hepatocytes in rats with alcoholic liver disease

Effect of tea polyphenols on TNF-α and hepatocytes in rats with alcoholic liver disease

Does adding milk remove the benefits of your daily cuppa?

. 2006). Thisinverse association was stronger in women; those con-suming at least five cups a day were 31% less likely todie from cardiovascular disease than those drinking onecup or less.A meta-analysis based on ten prospective cohort stud-ies and seven case–control studies, concluded that anincrease in daily black tea consumption of three cupsdecreased the risk of myocardial infarction by 11% [rel-ative risk 0.89, 95% confidence interval (CI) 0.79–1.01], although there was evidence of publication biasand geographical differences with benefits seen prima-rily in studies in continental Europe (Peters et al. 2001).In contrast, an inverse association between tea drinkingand heart disease has not been demonstrated by UKstudies. In fact, Woodward and Tunstall-Pedoe (1999)found a modest positive relationship between tea con-sumption and all-cause mortality, including coronaryheart disease in the Scottish Heart Study. However, thisstudy failed to control for important confounders asso-ciated with tea consumption and a recent review ofthe evidence has supported the benefits of regular teaconsumption for coronary heart disease prevention(Gardner et al. 2007).Some studies have also suggested that tea consump-tion may be associated with lower mortality amongindividuals with established cardiovascular disease. Forexample, Mukamal et al. (2002) followed 1900 patientswho had suffered a myocardial infarction for 3.8 yearsand reported lower all-cause mortality and cardiovascu-lar mortality among the moderate (<14 cups/week) andheavy tea drinkers (14 or more cups/week) comparedwith non-drinkers after controlling for a number of clin-ical and sociodemographic characteristics (hazard ratiofor all-cause mortality among moderate drinkers was0.72, 95% CI 0.55–0.94 and for heavy drinkers was0.56, 95% CI 0.37–0.84).In vitro and in vivo studies have suggested that thisreduced risk may be due to the antioxidant, anti-inflam-matory, antithrombogenic and vasodilating effects oftea polyphenols. Tea is rich in the polyphenolic com-pounds flavonoids, including catechins (particularly epi-gallocatechin-3-gallate), flavonols, theaflavins andthearubigins. Green tea leaves contain more catechinsowing to their high epigallocatechin-3-gallate content,while black tea leaves, which undergo oxidation duringmanufacturing, contain more complex thearubigins andtheaflavins (British Nutrition Foundation 2003). Tea fla-vonoids are released when boiling water is added andare known to be rapidly absorbed into the circulationfollowing oral ingestion. Human intervention trials sug-gest that tea consumption (up to six cups per day)impacts significantly on plasma antioxidant capacity(Rietveld & Wiseman 2003), although methodologicaldifferences, for example in assay methods, make studiesdifficult to compare. There is also evidence that thisantioxidant capacity of tea flavonoids may improveendothelial function, a sensitive parameter of vascularwall homeostasis, although the response varies betweenindividuals (Hodgson et al. 2006).Flavonoids are found in other foods and beverages,such as cocoa, fruits and vegetables and red wine, buttea is an important dietary source. In the UK, one studyestimated tea to account for 82% of total flavonoidintake (Hertog et al. 1997). Although no long-term ran-

Effects of tea polyphenols on the activities of α-amylase, pepsin, trypsin and lipase

Tea polyphenols (TP) possess many beneficial properties, such as reducing the risk of cancer and heart diseases, and acting as natural antioxidants for the food industry. At the same time, tea polyphenols might inhibit digestive enzymes and reduce food digestibility. To explore this possible antinutritional property, the effects of tea polyphenols on the activity of four typical digestive enzymes were investigated. HPLC analysis of the tea polyphenols extracted from Chinese green tea indicated that their catechin content was 93.6% (w/w), and that the content of ester bond-containing polyphenols was more than 82%. Measurement of the interaction of gelatin with tea polyphenols was first carried out, in order to model enzyme protein–TP interaction. It proved that tea polyphenols were capable of binding and precipitating protein, suggesting a potential ability of TP to denature digestive enzymes. In addition, the inhibitory effects of tea polyphenols on α-amylase, pepsin, trypsin and lipase were studied. In the presence of 0.05 mg/ml tea polyphenols, the inhibition ratios of α-amylase, pepsin, trypsin and lipase were, respectively, 61%, 32%, 38% and 54%, suggesting that TP might possess antinutritional properties.

Effects of Tea Polyphenols on Emulsification of Olive Oil in a Small Intestine Model System

Tea catechins have been shown to reduce plasma cholesterol and suppress hypertriacylglycerolemia by reducing triglyceride absorption. However, the mechanism is not yet clear. One of the possible mechanisms is that tea polyphenols may modify dietary fat emulsification in the gastrointestinal tract. The digestive enzyme (lipase) acts on specific emulsion interface properties (droplet size and surface area). Therefore, changes in these properties may modify emulsification and lead to changes in dietary fat digestion and absorption. In this study, the effect of both green and black tea on the changes of emulsification was examined by measuring the droplet size and the surface area. A model emulsion system containing olive oil, phosphatidylcholine (PC), and bile salt was developed to simulate small intestinal conditions. Initial changes in droplet size (from 1.4 to 52.8 microm and from 1.4 to 25.9 microm) of the emulsion were observed in the presence of 1.04 mg/mL and 0.10 mg/mL of total catechins prepared from green and black tea, respectively. Both teas caused similar changes on the emulsion properties; however, black tea was more effective than green tea. The underlying mechanisms of actions of tea polyphenols are discussed.

Effects of tea polyphenols on alcoholic liver injury in rats

Effects of tea polyphenols on alcoholic liver injury in rats

Protective effects of tea polyphenols on liver against triptolide-induced hepatic injury in mice

Protective effects of tea polyphenols on liver against triptolide-induced hepatic injury in mice

Effects of tea polyphenols on telomerase activity of a tongue cancer cell line: a preliminary study

The aim of this study was to determine, at the mRNA and protein levels, whether tea polyphenols (TPs) affect the expression of the human telomerase reverse transcriptase (hTERT) gene in the Tca8113 cancerous cell line. The expression of this gene was determined at the mRNA level by reverse transcription and polymerase chain reaction and at the protein level by Western blotting. The semi-quantitative scores of hTERT mRNA expression were analyzed by one-way analysis of variance. After 72 h of exposure to TPs, the mean (±SD) scores of hTERT mRNA expression in TP 0.1 g/l, TP 0.05 g/l and a control group were 0.32 ± 0.05, 0.41 ± 0.04 and 0.72 ± 0.05, respectively ( P < 0.05). The Western blot assay showed that TPs also decreased the expression of hTERT at the protein level. These results indicate that TPs reduce hTERT activity in the human Tca8113 cell line in a time- and dose-dependent manner, disabling telomerase activity and thereby terminating unlimited cancer cell proliferation. These findings suggest a mechanism behind TP's anticancer activity.

Bioavailability and antioxidant effect of epigallocatechin gallate administered in purified form versus as green tea extract in healthy individuals

Tea polyphenols have strong in vitro antioxidant activity. Due to their limited bioavailability, however, their contribution to in vivo antioxidant activity may depend on the form of administration. A human intervention study was performed to evaluate the bioavailability and antioxidant capacity of (−)-epigallocatechin-3-gallate (EGCG) administered as a single large dose in the form of either purified EGCG or as green tea extract (Polyphenon E). Plasma concentrations of tea polyphenols were determined by high-performance liquid chromatography (HPLC) analysis combined with coulometric array electrochemical detection (ECD). We found no differences in plasma EGCG concentrations and trolox equivalents determined by the trolox equivalent antioxidant capacity assay after administration of either form of EGCG. However, we found that the plasma antioxidant activity was significantly affected by changes in the plasma urate concentration, which may have interfered with the effect of tea polyphenols on the antioxidant activity. In addition, lymphocyte 8-hydroxydeoxyguanosine to deoxyguanosine (8-OHdG/10 6dG) ratios were determined by HPLC with ECD. The 8-OHdG/10 6dG ratios did not change significantly during the 24 h following both EGCG interventions but correlated significantly within individuals determined during the two interventions separated by 1 week. In summary, changes in plasma uric acid due to dietary intake were significantly correlated to the plasma antioxidant activity and exerted a stronger influence on the plasma antioxidant activity compared with the EGCG intervention. In future studies of dietary effects on the plasma antioxidant capacity, changes in plasma uric acid will need to be closely monitored.

Tea Polyphenols Inhibit Acetyl-CoA:1-Alkyl-sn-Glycero-3-Phosphocholine Acetyltransferase (a Key Enzyme in Platelet-Activating Factor Biosynthesis) and Platelet-Activating Factor-Induced Platelet Aggregation

Background: Tea extracts have antiallergic and anti-inflammatory actions in rats and mice. However the mechanism through which tea polyphenols act in vivo are still incompletely understood. We found inhibitory effects of black tea extracts on an fMLP-induced aggregating response in a rabbit platelet-polymorphonuclear leukocyte (PMN) system. Method: To elucidate whether 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) production in PMNs and/or PAF-stimulated platelet activation were inhibited, the effects of tea polyphenols were investigated on the enzyme activity of acetyl-CoA:1-alkyl-sn-glycero-3-phosphocholine acetyltransferase (EC 2.3.1.67), PAF biosynthesis in A23187-activated rabbit PMNs, and rabbit platelet aggregation. By comparing the inhibitory effects of 31 galloyl esters and gallic acid, the structure-inhibitory activity relationship was characterized. Results: Theaflavin and its galloyl esters and pentagalloyl glucose were found to be potent inhibitors of the acetyltransferase (IC₅₀ = 28–58 µM) and the PAF biosynthesis as well as (–)-epicatechin-3-O-gallate (IC₅₀ = 72 ± 13 µM) and (–)-epigallocatechin-3-O-gallate (IC₅₀ = 46 ± 6 µM). On the other hand, flavan-3-ols without galloyl group at C-3 and gallic acid did not show significant enzyme inhibition. In addition, theaflavin and its galloyl esters (IC₅₀ = 32–77 µM) and geranyl gallate, farnesyl gallate and geranylgeranyl gallate (IC₅₀ = 6.4–7.6 µM) were found to be potent inhibitors of PAF- and TPA-induced rabbit platelet aggregation but not A23187-induced aggregation. Conclusions: Theaflavin and its galloyl esters in black tea extract, and isoprenyl gallates were potent inhibitors of PAF synthesis and platelet aggregation and these activities may be relevant to the claimed therapeutic effects of tea extracts.