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Antioxidant activity of polyphenols in carob pods.

We extracted polyphenols from carob (Ceratonia siliqua L.) pods, and evaluated the in vitro antioxidant activity of the crude polyphenol fraction (CPP). The total polyphenol content in CPP determined by the Folin-Ciocalteu method was 19.2%. The condensed tannin content determined by the vanillin and proanthocyanidin assay systems was 4.37% and 1.36%, respectively. beta-Carotene bleaching, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, inhibition of lipid peroxidation by the erythrocyte ghost, and microsomal assay systems were used to evaluate the antioxidant activity. CPP showed a stronger inhibitory effect against the discoloration of beta-carotene than other polyphenol compounds such as catechins and procyanidins. CPP had weaker antioxidant activity in the DPPH free radical scavenging, the erythrocyte ghost, and microsomal systems than authentic polyphenol compounds at the same concentrations. The activity adjusted by the polyphenol concentration was, however, comparable to that of authentic polyphenol compounds. Considering most carob pods are discarded and not effectively utilized at present, these results suggested that carob pods could be utilized as a functional food or food ingredient.

Antioxidants↗

Influence of green tea polyphenol in rats with arginine-induced renal failure.

To determine whether green tea polyphenol ameliorates the pathological conditions induced by excessive dietary arginine, green tea polyphenol was administered to rats at a daily dose of 50 or 100 mg/kg body weight for 30 days with a 2% w/w arginine diet. In arginine-fed control rats, urinary and/or serum levels of guanidino compounds, nitric oxide (NO), urea, protein, and glucose increased significantly, while the renal activities of the oxygen species-scavenging enzymes superoxide dismutase (SOD) and catalase decreased, compared with casein-fed rats. However, rats given green tea polyphenol showed significant and dose-dependent decreases in serum levels of creatinine (Cr) and urea nitrogen and urinary excretion of Cr, and they exerted a slight reduction of nitrite plus nitrate, indicating that green tea polyphenol reduced the production of uremic toxins and NO. In addition, in arginine-fed rats the urinary urea, protein, and glucose level increases were reversed by the administration of green tea polyphenol. Moreover, in rats given green tea polyphenol the SOD and catalase activities suppressed by excessive arginine administration increased dose-dependently, implying the biological defense system was augmented as a result of free radical scavenging. These results suggest that green tea polyphenol would ameliorate renal failure induced by excessive dietary arginine by decreasing uremic toxin, and NO production and increasing radical-scavenging enzyme activity.

Animals↗

Tea polyphenols inhibit the transport of dietary phenolic acids mediated by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers.

It was previously reported that a fluorescent marker dye, fluorescein, is transported via the monocarboxylic acid transporter (MCT). Fluorescein transport was competitively inhibited by MCT substrates such as ferulic and salicylic acids. Tea polyphenols, in particular, epigallocatechin gallate (EGCg) and epicatechin gallate (ECg), inhibited the transport of fluorescein. Tea polyphenols also inhibited the transport of salicylic and ferulic acids, suggesting tea polyphenols might be substrates of MCT. However, the transepithelial flux of tea polyphenols was much lower than that of the MCT substrates and was inversely correlated with the paracellular permeability of Caco-2 cell monolayers. These findings suggest that tea polyphenols are not substrates but inhibitors of MCT. Furthermore, the transepithelial transport of these polyphenols is mainly via paracellular diffusion. However, directional transport of ECg and EGCg from the basolateral to the apical side was observed, indicating that the behavior of tea polyphenols in the intestinal epithelium is complex.

Biological Transport↗

Extracts enriched in different polyphenolic families normalize increased cardiac NADPH oxidase expression while having differential effects on insulin resistance, hypertension, and cardiac hypertrophy in high-fructose-fed rats.

Insulin resistance and oxidative stress act synergistically in the development of cardiovascular complications. The present study compared the efficacy of three polyphenolic extracts in their capacity to prevent hypertension, cardiac hypertrophy, increased production of reactive oxygen species (ROS) by the aorta or the heart, and increased expression of cardiac NAD(P)H oxidase in a model of insulin resistance. Rats were fed a 60%-enriched fructose food and were treated once a day (gavage) for 6 weeks with 10 mL/kg of water only (F group) or the same amount of solution containing a red grape skin polyphenolic extract enriched in anthocyanins (ANT), a grape seed extract enriched in procyanidins and rich in galloylated procyanidins (PRO), or the commercial preparation Vitaflavan (VIT), rich in catechin oligomers. All treatments were administered at the same dose of 21 mg/kg of polyphenols. Our data indicate that (a) the ANT treatment prevented hypertension, cardiac hypertrophy, and production of ROS, (b) the PRO treatment prevented insulin resistance, hypertriglyceridemia, and overproduction of ROS but had only minor effects on hypertension or hypertrophy, while (c) Vitaflavan prevented hypertension, cardiac hypertrophy, and overproduction of ROS. All polyphenolic treatments prevented the increased expression of the p91phox NADPH oxidase subunit. In summary, our study suggest that (a) the pathogeny of cardiac hypertrophy in the fructose-fed rat disease involves both hypertension and hyperproduction of ROS, (b) polyphenolic extracts enriched in different types of polyphenols possess differential effects on insulin resistance, hypertension, and cardiac hypertrophy, and (c) polyphenols modulate the expression of NAD(P)H oxidase.

Animals↗

Tentative identification of polyphenols in Sempervivum tectorum and assessment of the antimicrobial activity of Sempervivum L.

Polyphenols were isolated from sliced fresh leaves of Sempervivum tectorum. After 21 h of extraction by methanol and removal of chlorophyll, ethyl acetate was used to separate oligomeric and polymeric polyphenols: 0.07% of oligomeric and 0.13% of polymeric polyphenols were found. After acidic hydrolysis of the oligomeric polyphenols, it was established by TLC, HPLC, and FAB mass spectra that kaempferol was the unique aglycon of the three main oligomeric constituents of S. tectorum. Paper chromatography suggested delphinidol to be the only anthocyanidin detectable in the material obtained by acidic hydrolysis of the polymeric polyphenol fraction. After Haslam degradation of the same polymeric polyphenol fraction, only 4-thiobenzyl-(-)-epigallocatechin and 4-thiobenzyl-(-)-epigallocatechin-3-gallate were found and tentatively identified. We concluded that procyanidins of B2 type could be the major components of the polymeric polyphenol fraction of this plant. Antimicrobial activity of Sempervivum L. leaves against six of seven selected microorganisms was observed.

Anti-Bacterial Agents↗

Risks and safety of polyphenol consumption.

This article gives an overview of the potential hazards of polyphenol consumption, as reported during the round-table discussion at the 1st International Conference on Polyphenols and Health, held in Vichy, France, November 2003. Adverse effects of polyphenols have been evaluated primarily in experimental studies. It is known, for example, that certain polyphenols may have carcinogenic/genotoxic effects or may interfere with thyroid hormone biosynthesis. Isoflavones are of particular interest because of their estrogenic activity, for which beneficial as well as detrimental effects have been observed. Furthermore, consumption of polyphenols inhibits nonheme iron absorption and may lead to iron depletion in populations with marginal iron stores. Finally, polyphenols may interact with certain pharmaceutical agents and enhance their biologic effects. It is important to consider the doses at which these effects occur, in relation to the concentrations that naturally occur in the human body. Future studies evaluating either beneficial or adverse effects should therefore include relevant forms and doses of polyphenols and, before the development of fortified foods or supplements with pharmacologic doses, safety assessments of the applied doses should be performed.

Animals↗

Study on the determination of polyphenols in tobacco by HPLC coupled with ESI-MS after solid-phase extraction.

A high-performance liquid chromatography method coupled with electrospray ionization-mass spectrometry for the determination of polyphenols in tobacco is studied. The polyphenols are extracted from a tobacco sample by being refluxed in a boiling water bath with 80% methanol and purified by solid-phase extraction with a C18 cartridge. The chlorogenic acid, rutin, scopoletin, caffeic acid, scopolin, and other polyphenols are satisfactorily separated on a Nova-Pak C18 chromatographic column (3.9 x 150 mm) with methanol and 0.05 mol/L potassium dihydrogen phosphate buffer solution gradient elution as mobile phase at a flow rate of 0.5 mL/min. Each of the polyphenols is monitored by photodiode array detector at its maximum wavelength: chlorogenic acid, 326.1 nm; rutin, 354.8 nm; scopoletin, 344.0 nm; caffeic acid, 323.7 nm; and scopolin, 365.2 nm. The limits of detection are: 100 ng/mL for chlorogenic acid, 125 ng/mL for rutin, 60 ng/mL for scopoletin, 50 ng/mL for caffeic acid, and 100 ng/mL for scopolin. The key polyphenols in tobacco are identified by comparing the retention time, the UV-spectrum, and the mass spectra with those of the standards. The recovery of tobacco polyphenols is 94-105%, and the relative standard deviations are 1.28-1.49%. This method is successfully applied to qualitatively and quantitatively analyze the polyphenols in tobacco with good results.

Chromatography, High Pressure Liquid↗

Cardioprotective effects of dietary polyphenols.

Dietary polyphenols have been shown to possess cardioprotective effects. For example, the most noted role of grape polyphenols is in the French Paradox, in which a diet high in saturated fat accompanied by regular consumption of red wine is associated with a low risk of coronary heart disease (CHD). Initially, the paradox was thought to be driven by the postulated major action of grape polyphenols in inhibiting LDL oxidation. Although many studies have shown inhibitory effects of polyphenols on LDL oxidation, there have been an equal number of studies that showed a null effect on this variable. Although there are contrasting viewpoints on the effects of polyphenols on LDL oxidation variables, there is increasing evidence that these compounds possess additional cardioprotective functions including altering hepatic cholesterol absorption, triglyceride assembly and secretion, the processing of lipoproteins in plasma, and inflammation. It is the purpose of this review to examine recent information on the multiple functions of dietary polyphenols, with an emphasis on grape polyphenols, in decreasing the risk of CHD by improving plasma lipid profiles and reducing inflammation.

Animals↗

Polyphenols enhance platelet nitric oxide by inhibiting protein kinase C-dependent NADPH oxidase activation: effect on platelet recruitment.

Several studies demonstrated an inverse association between polyphenol intake and cardiovascular events. Platelet recruitment is an important phase of platelet activation at the site of vascular injury, but it has never been investigated whether polyphenols influence platelet recruitment. The aim of the study was to analyze in vitro whether two polyphenols, quercetin and catechin, were able to affect platelet recruitment. Platelet recruitment was reduced by NO donors and by NADPH oxidase inhibitors and was enhanced by L-NAME, an inhibitor of NO synthase. Quercetin and catechin, but not single polyphenol, significantly inhibited platelet recruitment in a concentration-dependent fashion. The formation of superoxide anion was significantly inhibited in platelets incubated with quercetin and catechin but was unaffected by a single polyphenol. Incubation of platelets with quercetin and catechin resulted in inhibition of PKC and NADPH oxidase activation. Treatment of platelets with quercetin and catechin resulted in an increase of NO and also down-regulated the expression of GpIIb/IIIa glycoprotein. This study shows that the polyphenols quercetin and catechin synergistically act in reducing platelet recruitment via inhibition of PKC-dependent NADPH oxidase activation. This effect, resulting in NO-mediated platelet glycoprotein GpIIb/IIIa down-regulation, could provide a novel mechanism through which polyphenols reduce cardiovascular disease.

Adult↗

Physiological activity of irradiated green tea polyphenol on the human skin.

Physiological activity of irradiated green tea polyphenol on the human skin was investigated for further industrial application. The green tea polyphenol was separated and irradiated at 40 kGy by y-ray. For an anti-wrinkle effect, the collagenase inhibition effect was higher in the irradiated sample (65.3%) than that of the non-irradiated control (56.8%) at 200 ppm of the concentration (p < 0.05). Collagen biosynthesis rates using a human fibroblast were 19.4% and 16.3% in the irradiated and the non-irradiated polyphenols, respectively. The tyrosinase inhibition effect, which is related to the skin-whitening effect, showed a 45.2% and 42.9% in the irradiated and the non-irradiated polyphenols, respectively, at a 100 ppm level. A higher than 90% growth inhibition on skin cancer cells (SK-MEL-2 and G361) was demonstrated in both the irradiated and the non-irradiated polyphenols. Thus, the irradiation of green tea polyphenol did not change and even increased its anti-wrinkle, skin-whitening and anticancer effects on the human skin. The results indicated that irradiated green tea polyphenol can be used as a natural ingredient with excellent physiological functions for the human skin through cosmetic or food composition.

Antineoplastic Agents↗

Wine polyphenols decrease blood pressure, improve NO vasodilatation, and induce gene expression.

The effects of short-term oral administration of red wine polyphenolic compounds on hemodynamic parameters and on vascular reactivity were investigated in rats. Endothelial function and vascular smooth muscle contractility were studied in association with the induction of gene expression in the vascular wall. Rats were treated daily for 7 days by intragastric administration of either 5% glucose or red wine polyphenolic compounds (20 mg/kg). Administration of these compounds produced a progressive decrease in systolic blood pressure, which became significantly different on day 4. Aortas from rats treated with red wine polyphenolic compounds displayed increased endothelium-dependent relaxation to acetylcholine that was related to increased endothelial NO activity and involved a mechanism sensitive to superoxide anion scavengers. However, no increase in whole-body oxidative stress has been observed in rats treated with red wine polyphenolic compounds, as shown by plasma glutathione assay. Also, in the aorta, red wine polyphenolic compounds increased the expression of cyclooxygenase-2 and increased the release of endothelial thromboxane A(2), which compensated for the extraendothelial NO-induced hyporeactivity in response to norepinephrine, resulting from enhanced inducible NO synthase expression. The present study provides evidence that short-term oral administration of red wine polyphenolic compounds produces a decrease in blood pressure in normotensive rats. This hemodynamic effect was associated with an enhanced endothelium-dependent relaxation and an induction of gene expression (of inducible NO synthase and cyclooxygenase-2) within the arterial wall, which together maintain unchanged agonist-induced contractility. These effects of red wine polyphenolic compounds may be a potential mechanism for preventing cardiovascular diseases.

Animals↗

Antimicrobial activity of 10 different plant polyphenols against bacteria causing food-borne disease.

The antibacterial activities of 10 different plant polyphenols were evaluated by comparing their minimum inhibitory concentrations (MICs) against several food-borne pathogenic bacteria, Staphylococcus aureus (20 strains), some serotypes of the genus Salmonella (26 strains), Escherichia coli (23 strains), and some species of the genus Vibrio (27 strains). The polyphenols examined were epigallocatechin (1), epigallocatechin-3-O-gallate (2), punicalagin (3), tannic acid (4), castalagin (5), prodelphinidin (6), geraniin (7), procyanidins (8), a theaflavin mixture of black tea (9), and green tea polyphenols treated with loquat polyphenol oxidase (10). The average MICs of all polyphenols against S. aureus and the genus Vibrio (192+/-91 and 162+/-165 microg/ml, respectively) were much lower than the values against the genus Salmonella and E. coli (795+/-590 and 1519+/-949 microg/ml, respectively) (p<0.01). The coefficient of variation of the MICs of all polyphenols against S. aureus was the least and that against the genus Vibrio was the greatest. The mean MICs of each plant polyphenol against S. aureus (98-389 microg/ml) and the genus Vibrio (68-488 microg/ml) were similar. The relatively lower mean MIC values of 1, 2, 5, and 6 suggest the importance of 3,4,5-trihydroxyphenyl groups in antibacterial activity.

Anti-Bacterial Agents↗

Polyphenols stimulate AMP-activated protein kinase, lower lipids, and inhibit accelerated atherosclerosis in diabetic LDL receptor-deficient mice.

Because polyphenols may have beneficial effects on dyslipidemia, which accelerates atherosclerosis in diabetes, we examined the effect of polyphenols on hepatocellular AMP-activated protein kinase (AMPK) activity and lipid levels, as well as hyperlipidemia and atherogenesis in type 1 diabetic LDL receptor-deficient mice (DMLDLR(-/-)). In HepG2 hepatocytes, polyphenols, including resveratrol (a major polyphenol in red wine), apigenin, and S17834 (a synthetic polyphenol), increased phosphorylation of AMPK and its downstream target, acetyl-CoA carboxylase (ACC), and they increased activity of AMPK with 200 times the potency of metformin. The polyphenols also prevented the lipid accumulation that occurred in HepG2 cells exposed to high glucose, and their ability to do so was mimicked and abrogated, respectively, by overexpression of constitutively active and dominant-negative AMPK mutants. Furthermore, treatment of DMLDLR(-/-) mice with S17834 prevented the decrease in AMPK and ACC phosphorylation and the lipid accumulation in the liver, and it also inhibited hyperlipidemia and the acceleration of aortic lesion development. These studies 1) reveal that inactivation of hepatic AMPK is a key event in the pathogenesis of hyperlipidemia in diabetes, 2) point to a novel mechanism of action of polyphenols to lower lipids by activating AMPK, and 3) emphasize a new therapeutic avenue to benefit hyperlipidemia and atherosclerosis specifically in diabetes via activating AMPK.

AMP-Activated Protein Kinases↗

[Direct detoxification of N-acetoxy-PhIP by tea polyphenols: a possible mechanism for chemoprevention against PhIP-DNA adduct formation in vivo].

OBJECTIVE: We have shown that green tea inhibited food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP)-induced carcinogen-DNA adduct formation in rats, and this protective effect of tea appears not relote to the modifications of metabolic enzymes involved in PhIP metabolism. The aim of this study was to explore the direct reaction of tea and tea polyphenols with N-acetoxy-PhIP, an ultimate carcinogen of PhIP formed via metabolic activation. METHODS: DNA binding assays were conducted to examine the effect of aqueous extract of tea and tea polyphenols on the reaction of [3H]N-acetoxy-PhIP with DNA. The reaction mixtures were analyzed by HPLC for the possible product (s) formed by the reaction of [3H]N-acetoxy-PhIP with tea polyphenols. RESULTS: It was found that agueous extract of tea and tea polyphenols strongly inhibited covalent binding of [3H]N-acetoxy-PhIP to DNA, and the inhibition was concentration-dependent with respect to inhibitors. HPLC analyses of reaction mixture containing [3H]N-acetoxy-PhIP and tea polyphenols revealed the production of the parent amine, PhIP, indicating a redox mechanism. CONCLUSION: In view of the presence of tea polyphenols in rat and human plasma after ingestion of tea, these results suggest that direct reduction of ultimate carcinogen N-acetoxy-PhIP by tea polyphenols is likely to be involved in the mechanism of chemoprevention of tea against PhIP-DNA adduct formation in vivo.

Animals↗

[Ecological feedback significance of polyphenols in organic layer of forest soil].

By comparing polyphenols (total polyphenols and condensed tannin) and other chemical and biological properties in soil organic layers during the transformation and regeneration of pure mature spruce stand in middle Europe, the functions of polyphenols in forest ecosystem were approached. The results showed that polyphenols concentration had a significant positive correlation with effective cation exchange capacity (ECEC), but no relation with organic C. The net N mineralization had no significant correlation with total polyphenols, organic C and C/N ratio, but had a significant negative correlation with condensed tannin. Polyphenols concentration also positively correlated with 1 mol.L.-1 KCl extractable C and N. It is suggest that although the polyphenols have no obvious physiological function in tree metabolism, it should be paid attention to its ecological feedback significance in the whole ecosystem.

Ecology↗

Inhibitory effect of tea polyphenols on renal cell apoptosis in rat test subjects suffering from cyclosporine-induced chronic nephrotoxicity.

OBJECTIVE: To investigate the inhibitory effect of tea polyphenols on renal cell apoptosis in rat test subjects suffering from cyclosporine A (CsA)-induced chronic nephrotoxicity. METHODS: Four groups of rats with CsA-induced chronic nephrotoxicity were respectively treated with vehicle olive oil, tea polyphenols, CsA and tea polyphenols plus CsA. At the end of the 28th day of treatment, 24 hours urine and blood samples were obtained, and the animals were then sacrificed. The serum and urine samples were analysed for creatinine clearance, and kidney tissue was used for pathologic analysis of renal tubular injury and interstitial fibrosis. The TUNEL assay, apoptosis-related enzyme caspase-3 mRNA detected by RT-PCR, and its enzymatic activity were analysed for the possible detections of cell apoptosis. RESULTS: CsA-treated rats displayed increased apoptosis of the tubular and interstitial cells, in comparison with vehicle-treated controls (18.3 +/- 4.6 vs 4.8 +/- 1.3 cells/mm(2), P < 0.05). In comparison with animals treated by CsA, animals treated with CsA plus tea polyphenols demonstrated significantly improved levels of creatinine clearance (0.12 +/- 0.03 vs 0.22 +/- 0.02 ml.min(-1).100 g(-1) body weight, P < 0.05), tubular injury (2.29 +/- 0.43 vs 1.42 +/- 0.26, P < 0.05), and interstitial fibrosis (2.83 +/- 0.20 vs 1.46 +/- 0.19, P < 0.05), and showed a statistically significant decrease in tubular and interstitial cell apoptosis (18.3 +/- 4.6 vs 7.7 +/- 2.1 cells/mm(2), P < 0.05). The expression of caspase-3 mRNA and caspase-3 activity was significantly higher in the CsA-treated group than that of the CsA plus tea polyphenols (TP)-treated group (P < 0.05). CONCLUSION: These results suggested that tea polyphenols significantly inhibits apoptosis of the tubular and interstitial cells in rats with cyclosporine-induced chronic nephrotoxicity, and that tea polyphenols may be useful to prevent CsA-associated kidney toxicity.

Animals↗

[Green tea polyphenols inhibit low-density lipoprotein-induced proliferation of rat vascular smooth muscle cells].

The proliferation and migration of vascular smooth muscle cells (VSMCs) is one of the major mechanisms of intimal thickening in atherosclerosis and post-angioplasty restenosis. Elevated plasma levels of low-density lipoprotein (LDL) have been implicated in the pathogenesis of atherosclerotic vascular diseases. The purpose of this study was to determine the effects of green tea polyphenols on the proliferation and p44/42 mitogen-activated protein kinase (MAPK) activity in rat VSMCs simulated by native LDL. Rat aortic VSMCs were cultured and treated with LDL (100 microg/ml) in the absence or presence of green tea polyphenols, and the cell proliferation was subsequently quantified by non-radioactive MTS/PES assay and the cell cycle analyzed by flow cytometry. The p44/42 MAPK activity was evaluated by immunoblotting using anti-p44/42 phospho-MAPK antibody. Compared with the cells without polyphenol treatment, the proliferation of the VSMCs induced by LDL was dose-dependently inhibited by green tea polyphenols (P<0.05), with more numerous cells in G(0)G(1) phase (P<0.05) as shown by flow cytometry analysis. LDL significantly enhanced the p44/42 MAPK activity, an effect obviously inhibited by green tea polyphenols (at 100 microg/ml). These results suggest that green tea polyphenols can inhibit high levels of LDL-induced proliferation of phosphorylated p44/42 MAPK expression in rat VSMCs. Green tea polyphenols may, therefore, offer vascular protection by inhibiting VSMC growth in response to hypercholesterolemia.

Animals↗

Effects of tea polyphenols on hepatic fibrosis in rats with alcoholic liver disease.

BACKGROUND: As an anti-oxidation agent, tea polyphenols may have the effect of anti-fibrosis. This study was designed to observe the effect of tea polyphenols on hepatic fibrosis in rats with alcoholic liver disease and to explore the related mechanisms. METHODS: Sixty healthy Sprague-Dawley rats were divided randomly into normal control group, single alcohol group, and three alcohol groups given different doses of tea polyphenols. Alcohol or isovolumic normal saline and corresponding doses of tea polyphenols were given daily to the rats separately. The rats were sacrificed at the end of the 24th week. Masson staining was performed to observe liver fibrosis, serum endotoxin, and oxidant and anti-oxidant activity. RESULTS: Hepatic fibrosis was less severe in the rats of the alcohol groups given tea polyphenols than in the single alcohol group. Tea polyphenols increased the serum anti-oxidant capacity and decreased the endotoxin level. CONCLUSION: Tea polyphenols show anti-fibrosis effect in rats with alcoholic liver disease, and the mechanism may be related to the clearance of overall oxidant and decrease of the endotoxin level.

Animals↗