Antioxidant Effects Of Polyphenols Research Articles

Polyphenols in obesity and weight management: Are they worth further research? An umbrella review.

Polyphenols are widely known for their putative antioxidant and anti-inflammatory effects and their potential protective role in several diseases such as type 2 diabetes, cardiovascular disease and cancer. They have also attracted significant interest as 'anti-obesity' agents, although with mechanisms of action that have been exclusively demonstrated in animal and invitro studies. This umbrella review aims to evaluate current evidence surrounding the role of polyphenols in obesity and weight management and to establish the usefulness of these agents in combatting obesity. A search of systematic reviews and meta-analyses of randomised controlled trials was carried out. Nine systematic reviews (of which eight included a meta-analysis) were included. Evidence of polyphenols' effects on reducing bodyweight is mixed, and where the effects are significant, they are numerically small and unlikely to be of help in reducing bodyweight or preventing weight gain. Future research should focus on establishing the anti-inflammatory and antioxidant effects of polyphenols through well-designed randomised controlled trials. Such research could be more valuable and cost-effective since it has shown potential to improve human health.

Urinary Nitric Oxide Levels Are Associated with Blood Pressure, Fruit and Vegetable Intake and Total Polyphenol Excretion in Adolescents from the SI! Program.

Nitric oxide (NO) is important to cardiovascular health (CVH), and its bioavailability could be regulated by the antioxidant effect of polyphenols, improving endothelial function and consequently blood pressure (BP). However, scant research has been carried out on NO and CVH correlates in adolescent populations. Therefore, our aim was to investigate the association between NO and the CVH status and other health factors in adolescents. NO, total polyphenol excretion (TPE), anthropometric measurements, BP, blood lipid profile, blood glucose, diet, physical activity, and smoking status were recorded, while CVH score was classified as ideal, intermediate, and poor. Negative associations were observed between NO and body mass index, body fat percentage, BP, and triglycerides; and positive associations between NO and skeletal muscle percentage, HDL-cholesterol, fruit and vegetable intake, and TPE was observed. To capture more complex interactions among different factors, multiple linear regression was performed, obtaining a significant association between NO and fruit and vegetable intake (β = 0.175), TPE (β = 0.225), and systolic BP (β = -0.235). We conclude that urinary NO levels are positively associated with the consumption of fruits and vegetables rich in antioxidants such as polyphenols and negatively associated with systolic BP.

Current State of Knowledge on the Antioxidant Effects and Mechanisms of Action of Polyphenolic Compounds

Quality-of-life improvements have resulted in increasing attention being paid to research on antiaging and antioxidation. Polyphenols are natural antioxidants with excellent biological activities, such as antioxidation and scavenging of free radicals and antiviral activity. Abundant availability and low toxicity of polyphenols have attracted the attention of researchers. In this paper, the antioxidant activities of flavonoids, phenolic acids, stilbenes and lignan polyphenols are analyzed, the corresponding antioxidant mechanisms are investigated, and the antioxidant effects of polyphenols are systematically reviewed. Thus, an effective reference based on the recent literature is compiled for the study of the antioxidant mechanisms of polyphenols that provides a significant theoretical basis for the development of products that are components of polyphenols.

Resveratrol, curcumin and gallic acid attenuate glyoxal-induced damage to rat renal cells

Glyoxal (GO), a by-product of glucose auto-oxidation, is involved in the glycation of proteins/ lipids and formation of advanced glycation (AGE) and lipoxidation (ALE) end products. AGE/ALE were shown to contribute to diabetic complications development/progression such as nephropathy. Diabetic nephropathy progression has an oxidative nature. Given the antioxidant effects of polyphenols, potential protective effects of resveratrol, curcumin and gallic acid, in rat renal cells treated with GO, were evaluated in the present work. According to our results, incubation of GO with the cells reduced their viability and led to membrane lysis, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential collapse, and lysosomal membrane leakage. These findings were prevented by pre-treatment with resveratrol, curcumin and gallic acid. Mitochondrial and lysosomal toxic interactions appear to worsen oxidative stress/cytotoxicity produced by GO. Resveratrol, curcumin and gallic acid inhibited ROS formation and attenuated GO-induced renal cell death.

Unfractionated green tea and ginger polyphenols induce apoptotic, cytotoxic and antioxidant effects in hepatoma cells

The objective of this work was to investigate the anti-proliferation, apoptotic and antioxidant effects of unfractionated polyphenols of green tea (GRTP) and ginger (GNRP), compared to cisplatin and ascorbic acid in human hepatocellular carcinoma. The cells’ growth rate and survival (MMT assay) were investigated in cells treated with different doses of polyphenols. The apoptotic fraction of treated cells was measured by flow cytometry, whereas the antioxidant effect of polyphenols was investigated in the presence or absence of thioacetamide (TAA), and compared to that of ascorbic acid. The results indicated that GRTP and GNRP, inhibited the growth rate of cells. GRTP was more cytotoxic, where cell viability of GRTP-treated cells was lower than cells treated with GNRP. The IC50 values were 39.3μg/ml and 64.9μg/ml, respectively. GRTP induced more apoptosis than GNRP or cisplatin. Moreover, the oxidative stress induced by TAA was challenged by GRTP, where reduced glutatione (GSH) in cells dually treated with GRTP/TAA was higher than untreated, GNRP/TAA and TAA/ascorbic acid treated cells. The data revealed the antihepatocarcinogenic effect of these polyphenols, where they triggered apoptosis and showed antioxidant effect in TAA treated cells. Green tea polyphenol was more antineoplasitic, apoptotic, compared to ginger polyphenols, and more antioxidant than ascorbic acid.

Molecular mechanisms of the cardiovascular protective effects of polyphenols

Epidemiological studies have reported a greater reduction in cardiovascular risk and metabolic disorders associated with diets rich in polyphenols. The antioxidant effects of polyphenols are attributed to the regulation of redox enzymes by reducing reactive oxygen species production from mitochondria, NADPH oxidases and uncoupled endothelial NO synthase in addition to also up-regulating multiple antioxidant enzymes. Although data supporting the effects of polyphenols in reducing oxidative stress are promising, several studies have suggested additional mechanisms in the health benefits of polyphenols. Polyphenols from red wine increase endothelial NO production leading to endothelium-dependent relaxation in conditions such as hypertension, stroke or the metabolic syndrome. Numerous molecules contained in fruits and vegetables can activate sirtuins to increase lifespan and silence metabolic and physiological disturbances associated with endothelial NO dysfunction. Although intracellular pathways involved in the endothelial effects of polyphenols are partially described, the molecular targets of these polyphenols are not completely elucidated. We review the novel aspects of polyphenols on several targets that could trigger the health benefits of polyphenols in conditions such as metabolic and cardiovascular disturbances.

Role of Mangifera indica bark polyphenols on rat gastric mucosa against ethanol and cold-restraint stress

This study was carried out in order to investigate the potential and antioxidant effects of polyphenols from Mangifera indica stem bark against gastric damage induced by ethanol and cold-restraint stress. The polyphenols possess good capacity for scavenging nitric oxide (NO) radical and ferric-reducing antioxidant power (FRAP) assay in vitro. Rats were sacrificed after the experiment, and their stomachs were removed for biochemical and histopathological analysis. The severity of lesions was found to markedly decrease by the administration of polyphenols in both models. The increased gastric nitrite level of ethanol administered rats were significantly (p < 0.001) reduced by polyphenol treatment. Administration of polyphenols reduced thiobarbituric acid reactive substance (TBARS) level and increased the GSH level significantly in a dose-dependent manner in both models. Our study revealed the ulcer-protective effects of the polyphenols and could possibly reside for the most part on its anti-radical effects.

ANTIOXIDANT STATUS IN VIVO: THE CASE FOR REGULAR CONSUMPTION OF ANTIOXIDANT RICH FRUITS AND VEGETABLES

ANTIOXIDANT STATUS IN VIVO: THE CASE FOR REGULAR CONSUMPTION OF ANTIOXIDANT RICH FRUITS AND VEGETABLES

Antidiabetic and antioxidant effects of polyphenols in brown alga Ecklonia stolonifera in genetically diabetic KK-A(y) mice.

The dietary intake and control of blood glucose levels are very important in hyperglycemic patients and alpha-glucosidase inhibitors are a cost-effective means to preventing the progression of diabetes. In search of a natural inhibitor from food materials, alpha-glucosidase inhibitory activity and the anti-hyperglycemic effects of a brown alga, Ecklonia stolonifera, were investigated using non-insulin dependent diabetic mice. Methanolic extract of E. stolonifera (MEE), which contains a high content of polyphenols, showed strong inhibition of alpha-glucosidase in vitro. Male KK-A(y) mice, a genetically non-insulin dependent diabetic model, showed hyperglycemia with aging, but the ingestion of MEE suppressed the increase in plasma glucose and lipid peroxidation levels in unfasted KK-A(y) mice dose dependently. In KK-A(y) mice, which were fed the MEE diet for 4 weeks, MEE moderated the elevation of plasma glucose levels after the oral administration of maltose. The polyphenols in MEE were estimated to be phlorotannins by HPLC-PDA and LC/MS analyses. These results demonstrate that E. stolonifera, seaweed typically used as a health food, has strong antidiabetic and antioxidant effects in vivo, thus, it may have beneficial properties in the prevention of diabetes and could be useful in the development of an antidiabetic pharmaceutical and functional food.

Different antioxidant effects of polyphenols on lipid peroxidation and hydroxyl radicals in the NADPH-, Fe-ascorbate- and Fe-microsomal systems

Antioxidant and pro-oxidant effects of 14 naturally occurring polyphenols (PP) on rat liver microsomal lipid peroxidation (LP) and hydroxyl radical ( OH) production were studied in NADPH-dependent, 50 μM Fe 2+–500 μM ascorbate (Fe–AA) or 50 μM Fe 2+ system, respectively. LP determined by the thiobarbituric acid method was inhibited in the NADPH system by flavonols and trans-resveratrol that were more effective than other flavonoids and derivatives of benzoic and cinnamic acid and were mostly more efficient than in the Fe–AA system. Inhibition of LP in the Fe system was higher by one order of magnitude than in the Fe–AA system. OH production in the NADPH system, measured by formaldehyde production, was decreased by myricetin, fisetin and quercetin, but increased by kaempferol, morin and trans-resveratrol, indicating that OH played a minor role in LP, which all of these PP inhibited. None of these PP at up to 40 μM concentration quenched OH in the Fe–AA system. All tested PP, except trans-resveratrol and gentisic acid, spectrally interacted with Fe 2+ or Fe 3+, indicating formation of complexes or oxidation of PP. In contrast to the NADPH system we found no correlation between Fe 2+ chelation and inhibition of Fe–AA- or Fe-dependent LP indicating that iron chelation did not play a significant role in the two latter systems. It is concluded that the inhibition of LP by PP was apparently due to their hydrogen donating properties rather than chelation of iron.

Antioxidant Effects of Polyphenols in Chocolate on Low-Density Lipoprotein both In Vitro and Ex Vivo.

Cacao is rich in polyphenols such as (-)-epicatechin, and a colored component of cacao (cacao-red) is polyphenol, which is an antioxidant. These properties stimulated an investigation of the effects of cacao liquor polyphenols (CLP) on low-density lipoprotein (LDL) oxidation. The 2.2 '-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMVN-CH2O)-induced oxidizability of LDL was assessed by monitoring the absorbance at 234 nm. In vitro. 0.1-0.5 mg/dL CLP prolonged the oxidation lag time of LDL in a dose-dependent manner. Compared with the controls, it was prolonged 1.7-fold in the presence of 0.1 mg/dL CLP, 2.9-fold at 0.2 mg/dL, 3.8-fold at 0.3 mg/dL, 5.4-fold at 0.4 mg/dL, and 6.4-fold at 0.5 mg/dL. Furthermore, we enlisted 13 male volunteers to consume 35 g delipidated cocoa. Venous blood samples were taken before and at 2 h and 4 h after consuming the cocoa. The oxidation lag time of LDL before cocoa ingestion was 59.0 +/- 6.3 min, but it was prolonged at 2 h after cocoa (68.3 +/- 6.0 min); before returning to the initial lag time (61.7 +/- 5.7 min) before consumption. Thus we have shown that cocoa inhibited LDL oxidation both in vitro and ex vivo.