Polarographic study of hydrogen peroxide anodic current and its application to antioxidant activity determination

Behavior of hydrogen peroxide in alkaline medium has been studied by direct current (DC) polarography with dropping mercury electrode (DME) aiming to apply it in antioxidant (AO) activity determination. Development of a peroxide anodic current having form of a peak, instead of common polarographic wave, has been investigated. As a base for this investigation the interaction of H(2)O(2) with anodically dissolved mercury was followed. Formation of mercury complex [Hg(O(2)H)(OH)] has been confirmed. The relevant experimental conditions, such as temperature, concentration and pH dependence, as well as time stability of hydrogen peroxide anodic current, have been assessed. Development of an AO assay based on decrease of anodic current of hydrogen peroxide in the presence of antioxidants (AOs) has been described. Under optimized working conditions, a series of benzoic acids along with corresponding cinnamate analogues have been tested for hydrogen peroxide scavenging activity. In addition, the assay versatility has been confirmed on various complex samples. (C) 2011 Elsevier B.V. All rights reserved

Antioxidant Activity of Wines Determined by a Polarographic Assay Based on Hydrogen Peroxide Scavenge

Antioxidant (AO) activity of various red and white wines of different origin as well as some individual phenolic compounds present in wine has been assessed using a polarographic assay. Direct current polarography has been used to survey hydrogen peroxide scavenge (HPS) upon gradual addition of tested samples. Results expressed as reciprocal value of wine volume required for 50% decrease of anodic limiting current of hydrogen peroxide have been validated through correlation with Folin Ciocalteau and DPPH assays. All wines exhibit HPS activity analogous with total phenolic content and DPPH scavenge. Reliability and accuracy, low cost, and rapid and direct experimental procedure open a wide area for application of this assay, making it a good alternative to standard, widely accepted AO assays

Application of a Novel Antioxidative Assay in Beer Analysis and Brewing Process Monitoring

A novel antioxidative assay based on direct current polarography has been developed. Quantification of antioxidative (AO) activity has been based on a decrease of hydrogen peroxide anodic current in the presence of antioxidants. An efficient experimental procedure, without any special pretreatment of analyzed samples, has been applied. Antioxidative activity of different kinds of commercial beers (dark, blond, and alcohol-free), some small-scale made special beers with medicinal herbs and Mushroom extracts, extracts themselves, as well as individual phenolic components present in beer has been measured. In addition, changes of AO activity during the full-scale industrial process of beer production have been monitored. A strong correlation between results obtained and total phenolics content has been observed. The assay can be recommended for application in brewing industry, either to survey 1 process with the aim to optimize relevant technological factors or to analyze quality of final product

Antioxidant activity of propolis extracts from Serbia: A polarographic approach

Antioxidant activity (AO) of commercial propolis extracts (PEs), available on Serbian market, was determined by direct current (DC) polarography. Polarographic anodic current of 5.0 mmol L-1 alkaline solution of H2O2 was recorded at potentials of mercury dissolution. Decrease of the current was plotted against the volume of gradually added PEs. The volume of PE causing 20% current decrease was determined from the linear part of the plot. Antioxidant activity was expressed in H2O2 equivalent (HPEq), representing the volume of PE that corresponds to 1.0 mmol L-1 H2O2 decrease. Resulting HPEq ranged between 1.71 +/- 0.11 and 8.00 +/- 0.18 mu L. Range of 1,1-dipheny1-2-picryl hydrazyl (DPPH) radical scavenging activity was from 0.093 +/- 0.004% to 0.346 +/- 0.006%. Total phenolic content (TCP) of PE with superior AO activity was 5.31 +/- 0.05%g GAE, while the extract with the lowest activity contained 1.45 +/- 0.02%g GAE. Antioxidant activity, determined by polarographic method, was correlated with DPPH scavenging activity (R-2 = 0.991) and TCP (R-2 = 0.985). Validity of obtained results was further confirmed using ANOVA and post hoc Tukey HSD test

Comparative analysis of antioxidant activity of honey of different floral sources using recently developed polarographic and various spectrophotometric assays

Hydrogen peroxide scavenging (HPS) activity of honey of different floral sources and its constituents such as predominant honey flavonoids, phenolic acids, amino and organic acids, and carbohydrates have been assessed by direct current (DC) polarographic assay. The assay was based on decrease of anodic current of hydrogen peroxide complex, formed in alkaline solution, at the potential of mercury dissolution. High correlations between honey HPS activity, its total phenolic content (FC-GAE), antioxidant activity measured by four standard methods (DPPH, TEAC, FRAP and ORAC), and also the relative antioxidant capacity index, were obtained. Statistical evaluation by ANOVA and F-test further confirmed the assay validity. The results for individual compounds showed that HPS activity of honey reflects an integrated action of a wide range of constituents, both phenolics and non-phenolics. The polarographic assay applied is a fast, reliable and low cost alternative to spectrophotometric antioxidant assays commonly applied in analysis of honey and can serve as an indicator of honey quality

Cold-Pressed Pumpkin Seed Oil Antioxidant Activity as Determined by a DC Polarographic Assay Based on Hydrogen Peroxide Scavenge

Antioxidant (AO) activity of cold pressed pumpkin (Cucurbita pepo L.) seed oil, produced from three naked and one hulled variety, was assessed using a DC polarographic assay based on a hydrogen peroxide scavenge (HPS). Results are expressed as the decrease of the anodic oxidation current of hydrogen peroxide obtained upon addition of methanolic extract of the investigated oils. Strict correlations of HPS and (1) radical scavenging capacity against the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) (0.99), (2) the induction period estimated by a Rancimat test (0.99) and (3) total phenolic content estimated by Folin-Ciocalteu (FC) assay (0.99) were obtained. In addition, a significant correlation of HPS and the content of delta-tocopherol (0.87), squalene (0.67) and color CIE a* (-0.89) was found. Based on the results reported, the polarographic assay was found to be suitable for determination of AO activity as an indicator of the quality and oxidative stability of oil

Changes of Hydrogen Peroxide and Radical-Scavenging Activity of Raspberry during Osmotic, Convective, and Freeze-Drying

This study was conducted to investigate the influence of different drying treatments on antioxidant (AO) activity and phenolic content of raspberry (Rubus idaeus), cultivar Willamette. Whole raspberry fruits were dried convectively (air-drying), osmotically, and freeze-dried. Acetone-water extracts of fresh and dried raspberries were assessed for total phenolic content by standard Folin-Ciocalteau method. Two AO assays were applied, a recently developed direct current (DC) polarographic assay based on decrease of anodic oxidation current of hydrogen peroxide and widely used radical scavenge against the 1,1-diphenyl-2-picrylhydrazyl (DPPH). Strong correlation has been obtained between both AO assays and total phenolic content. In addition, some individual phenolic compounds present in raspberry have been assessed using DPPH and DC polarographic assay. Comparison and evaluation of drying methods has been based on preservation of AO activity and total phenolic content. Obtained results confirmed superiority of freeze-drying; convective drying caused slight changes while osmotic dehydration showed a significant decrease of phenolic compounds and AO activity. Practical Application Optimization of drying process could be based on surveying of AO activity

Antioxidant efficiency of polyphenols from coffee and coffee substitutes-electrochemical versus spectrophotometric approach

Antioxidant (AO) capacity of instant, espresso, filter and Turkish/Greek coffee brews, coffee substitutes (roasted chicory root, barley, pea, chickpea, carob and dried fig) and individual compounds (phenolic acids, flavonoids, methylxanthines, N-methyl pyridinium and HMW melanoidins) was assessed using DC polarographic assay based on decrease of anodic current originating from hydroxo-perhydroxo mercury complex formed in alkaline solutions of H2O2 at potential of mercury dissolution, as well as three spectrophotometric assays (DPPH, ABTS and FRAP). A large difference between applied assays ability to recognize various types of individual AOs was noticed. Only according to DC polarographic assay significant AO activity was ascribed to methylxanthines and N-methyl pyridinum. The total content of phenolics (TPC) present in complex samples was determined by FC assay. The highest TPC was ascribed to instant coffees and coffee substitutes while the lowest to decaffeinated filter coffee. Complex samples were grouped based on principal components analysis, phenolics AO coefficient, calculated as the ratio between AO capacity and TPC, and relative AO capacity index (RACI), calculated by assigning equal weight to all applied assays including FC. The highest values of RACI were ascribed to instant coffee brews, followed by substitutes while the lowest to the decaffeinated espresso coffee