Kanti Bhooshan Pandey

Plant Polyphenols as Dietary Antioxidants in Human Health and Disease

Polyphenols are secondary metabolites of plants and are generally involved in defense against ultraviolet radiation or aggression by pathogens. In the last decade, there has been much interest in the potential health benefits of dietary plant polyphenols as antioxidant. Epidemiological studies and associated meta-analyses strongly suggest that long term consumption of diets rich in plant polyphenols offer protection against development of cancers, cardiovascular diseases, diabetes, osteoporosis and neurodegenerative diseases. Here we present knowledge about the biological effects of plant polyphenols in the context of relevance to human health.

Markers of Oxidative Stress in Erythrocytes and Plasma During Aging in Humans

Aging is an inevitable universal biological process, which can be characterized by a general decline in physiological function with the accumulation of diverse adverse changes and increased probability of death. Among several theories, oxidative stress/free radical theory offers the best mechanistic elucidation of the aging process and other age-related phenomenon. In the present paper, we discuss the aging process and have focused on the importance of some reliable markers of oxidative stress which may be used as biomarkers of the aging process.

Markers of Oxidative Stress during Diabetes Mellitus

The prevalence of diabetes mellitus is rising all over the world. Uncontrolled state of hyperglycemia due to defects in insulin secretion/action leads to a variety of complications including peripheral vascular diseases, nephropathy, neuropathy, retinopathy, morbidity, and/or mortality. Large body of evidence suggests major role of reactive oxygen species/oxidative stress in development and progression of diabetic complications. In the present paper, we have discussed the recent researches on the biomarkers of oxidative stress during type 2 diabetes mellitus.

Protein oxidation biomarkers in plasma of type 2 diabetic patients

OBJECTIVES To evaluate oxidative stress and the extent of oxidation of plasma proteins in type 2 diabetic patients. DESIGN AND METHODS Study was carried out on blood from 31 diabetic patients of both sexes (mean age = 58 + or - 7; duration of diabetes 12 + or - 5 years) and healthy age and sex matched normal subjects. Biomarkers of protein oxidation; plasma protein carbonyls (PCO), advanced oxidation protein products (AOPPs) and -SH group and free radical scavenging capacity of plasma was measured. RESULTS PCO and AOPPS levels were significantly (P<0.005) higher in diabetic patients in comparison to healthy volunteers. Reduced free radical scavenging capacity (P<0.001) and -SH group (P<0.05) was observed in plasma of type 2 diabetic patients. CONCLUSIONS Our data suggest that diabetics are susceptible to protein oxidation. Oxidative modulation of proteins due to reduced radical scavenging activity of plasma patients may be one of the reasons of altered physiological processes in type 2 diabetic patients.

Protective effect of resveratrol on markers of oxidative stress in human erythrocytes subjected to in vitro oxidative insult.

Resveratrol is a natural polyphenolic compound found largely in the skin of red grapes. Growing evidence suggests that resveratrol may play an important role in the prevention of many human diseases. Many of the biological actions of this polyphenol have been attributed to its antioxidant properties. The present study was undertaken to evaluate the effect of resveratrol on intracellular reduced glutathione (GSH) and membrane sulphydryl groups in erythrocytes subjected to oxidative stress in vitro by incubating with t‐BHP (10 µm). The study was aimed to test the efficacy of the antioxidant effect of resveratrol on human erythrocytes. Subjecting erythrocytes to oxidative stress (in vitro) by incubating them with t‐BHP (10 µm) caused a significant decrease in the intracellular GSH level and membrane –SH content compared with basal values. Incubation of erythrocytes/membranes with resveratrol (1–100 µm final conc) resulted in significant protection against the t‐BHP‐induced oxidative stress as evidenced by the increase in GSH level and membrane –SH content. It was observed that the effect of resveratrol is dose/concentration and time‐dependent. Since resveratrol is naturally present in many fruits and vegetables, a diet rich in resveratrol may provide protection against degenerative diseases. Copyright

Protective effect of resveratrol on formation of membrane protein carbonyls and lipid peroxidation in erythrocytes subjected to oxidative stress.

Many of the biological actions of resveratrol have been attributed to its antioxidant properties. In this work, we subjected human erythrocytes to in vitro oxidative stress by incubating them with tert-butylhydroperoxide (t-BHP). This caused a significant increase in the malondialdehyde (MDA) level and the protein carbonyl group content above the basal values. The presence of trans-resveratrol at micromolar concentrations in the incubation medium protected the erythrocytes from t-BHP-induced oxidative stress, as evidenced by the decrease in the MDA level and the protein carbonyl group content. The effect of resveratrol was concentration and time-dependent. Our findings help to explain some of the beneficial effects of resveratrol.

Plasma protein oxidation and its correlation with antioxidant potential during human aging

Previous studies have indicated that the main molecular characteristic of aging is the progressive accumulation of oxidative damages in cellular macromolecules. Proteins are one of the main molecular targets of age-related oxidative stress, which have been observed during aging process in cellular systems. Reactive oxygen species (ROS) can lead to oxidation of amino acid side chains, formation of protein-protein cross-linkages, and oxidation of the peptide backbones. In the present study, we report the age-dependent oxidative alterations in biomarkers of plasma protein oxidation: protein carbonyls (PCO), advanced oxidation protein products (AOPPs) and plasma total thiol groups (T-SH) in the Indian population and also correlate these parameters with total plasma antioxidant potential. We show an age dependent decrease in T-SH levels and increase in PCO and AOPPs level. The alterations in the levels of these parameters correlated significantly with the total antioxidant capacity of the plasma. The levels of oxidized proteins in plasma provide an excellent biomarker of oxidative stress due to the relative long half-life of such oxidized proteins.

Ascorbate recycling by erythrocytes during aging in humans.

Erythrocytes play a crucial role in recycling ascorbate in blood plasma. The erythrocyte ascorbate free radical (AFR) reductase is involved in the reduction of AFR to ascorbic acid (ASC) in the plasma. In the present study, we report an age-dependent increase in the activity of erythrocyte AFR reductase in humans that shows a significant positive correlation with the activity of plasma membrane redox system (PMRS). We explain the age-dependent increase in erythrocyte ASC recycling on the basis of a compensatory/protective mechanism that operates to maintain the ASC level in plasma and thereby minimize oxidative stress during aging.

Myricetin May Provide Protection against Oxidative Stress in Type 2 Diabetic Erythrocytes

Oxidative stress is believed to be a major contributing factor in the development of late complications of diabetes. Many in vitro and in vivo studies have demonstrated that several parameters of red blood cell function and integrity are negatively affected by increased oxidative stress. Plant polyphenols are reported to exert many biological effects due to their antioxidant property. The present study was undertaken to evaluate the antioxidant effect of myricetin on markers of oxidative stress in erythrocytes from type 2 diabetic patients. The study was carried out on blood samples obtained from 23 type 2 diabetic patients and 23 age-matched control subjects. Erythrocytes were subjected to in vitro oxidative stress by incubating with 10-5 M tert-butyl hydroperoxide (t-BHP). Erythrocyte membrane lipid peroxidation and protein oxidation were measured in terms of malondialdehyde (MDA) and protein carbonyl group levels. The results showed an elevated MDA and protein carbonyl content in diabetic erythrocytes which were further increased after incubation with t-BHP. Myricetin at micromolar concentration significantly (p < 0.01) protected an t-BHP-induced increase in levels of oxidative stress parameters of diabetic erythrocytes

Activation of the erythrocyte plasma membrane redox system by resveratrol: a possible mechanism for antioxidant properties

Resveratrol is one of the most widely studied of all the plant-produced polyphenols and has diverse, beneficial health effects including anti-cancer and cardio-protective effects. Many of the biological actions of this polyphenol have been attributed to its antioxidant properties. Erythrocytes contain a plasma membrane redox system (PMRS), which transfers electrons from intracellular donors (NADH and/or ascorbate (ASC)) to extracellular acceptors. There is evidence that the intracellular ASC donates electrons to extracellular ascorbate free radicals (AFRs) via the PMRS, which encompasses an AFR reductase; such a redox system enables the cells to effectively counteract oxidative processes.We present evidence to show that human erythrocytes take up resveratrol, and once inside the cell, resveratrol can donate electrons to extracellular electron acceptors through the erythrocyte PMRS and AFR reductase. Incubating human erythrocytes with resveratrol (10 μM) caused a significant activation of the PMRS (41%) and AFR reductase (30%) over (basal level) the control; the effect of resveratrol was concentration-dependent. The electron donating ability of resveratrol is slightly less than that observed with quercetin. The role of resveratrol in activating the erythrocyte PMRS and AFR reductase may assume significance in all disease conditions in which there is a decrease in plasma antioxidant potential.