Use of a Free Radical Method to Evaluate Antioxidant Activity
TL;DR: The antiradical properties of various antioxidants were determined using the free radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH*) in its radical form as discussed by the authors.
Abstract: The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.
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TL;DR: In this paper, the contribution of l-ascorbic acid (AA) to the total antioxidant activity of fruits was investigated by using RP-HPLC, which measured the change of absorbance of the free radical solution at 414 nm in the test reaction mixture following addition of the fruit extract, as compared with AA.
1,031 citations
TL;DR: This work proves applicability of the ORAC-FL assay in evaluating the antioxidant activity of diverse food samples and confirms influence of vintage, but not origin of the oak, in the antioxidants activity of wines from the same variety.
Abstract: The ORAC-fluorescein (ORAC-FL) method recently validated using automatic liquid handling systems has now been adapted to manual handling and using a conventional fluorescence microplate reader. As calculated for Trolox, the precision of the method was <3.0, expressed as percent coefficient of variation. The accuracy of the method was <2.3, expressed as percent variation of the mean. The detection and quantification limits were those corresponding to 0.5- and 1-microM Trolox standard solutions, respectively. The method has been applied to 10 pure compounds (benzoic and cinnamic acids and aldehydes, flavonoids, and butylated hydroxyanisole), to 30 white, rose, and bottled- and oak-aged red wines, and to 7 commercial dietary antioxidant supplements. All samples exhibited a good linear response with concentration. As seen by other methodologies, the chemical structure of a compound determines its antioxidant activity (ORAC-FL value). Of particular interest were the results with oak-aged red wines from different vintages (1989-2002) that confirm influence of vintage, but not origin of the oak, in the antioxidant activity of wines from the same variety. Dietary antioxidant supplements presented a great variability (170-fold difference) in their antioxidant potency. This work proves applicability of the ORAC-FL assay in evaluating the antioxidant activity of diverse food samples.
1,021 citations
TL;DR: The CAA assay is a more biologically relevant method than the popular chemistry antioxidant activity assays because it accounts for some aspects of uptake, metabolism, and location of antioxidant compounds within cells.
Abstract: A cellular antioxidant activity (CAA) assay for quantifying the antioxidant activity of phytochemicals, food extracts, and dietary supplements has been developed Dichlorofluorescin is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF) The method measures the ability of compounds to prevent the formation of DCF by 2,2′-azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells The decrease in cellular fluorescence when compared to the control cells indicates the antioxidant capacity of the compounds The antioxidant activities of selected phytochemicals and fruit extracts were evaluated using the CAA assay, and the results were expressed in micromoles of quercetin equivalents per 100 µmol of phytochemical or micromoles of quercetin equivalents per 100 g of fresh fruit Quercetin had the highest CAA value, followed by kaempferol, epigallocatechin gallate (EGCG), myricetin, and luteolin among the pure co
1,011 citations
TL;DR: Three hard winter wheat varieties were examined and compared for their free radical scavenging properties and total phenolic contents (TPC) and ESR results confirmed that wheat extracts directly reacted with and quenched free radicals.
Abstract: Three hard winter wheat varieties (Akron, Trego, and Platte) were examined and compared for their free radical scavenging properties and total phenolic contents (TPC) Free radical scavenging properties of wheat grain extracts were evaluated by spectrophotometric and electron spin resonance (ESR) spectrometry methods against stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH*) and radical cation ABTS*+ (2,2'-azino-di[3-ethylbenzthiazoline sulfonate]) The results showed that the three wheat extracts differed in their capacities to quench or inhibit DPPH* and ABTS*+ Akron showed the greatest activity to quench DPPH radicals, while Platte had the highest capacity against ABTS*+ The ED50 values of wheat extracts against DPPH radicals were 060 mg/mL for Akron, 71 mg/mL for Trego, and 095 mg/mL for Platte under the experimental conditions The trolox equivalents against ABTS*+ were 131 +/- 044, 108 +/- 005, and 191 +/- 006 micromol/g of grain for Akron, Trego, and Platte wheat, respectively ESR results confirmed that wheat extracts directly reacted with and quenched free radicals The TPC were 4879 +/- 9278 microg gallic acid equivalents/g of grain No correlation was observed between TPC and radical scavenging capacities for DPPH* and ABTS*+ (p = 015 and p > 05, respectively)
946 citations
TL;DR: This review intends to offer a critical evaluation of existing antioxidant assays applied to phenolics, and reports the development of a simple and low-cost antioxidant capacity assay for dietary polyphenols, vitamins C and E, and human serum antioxidants, which is named the CUPRAC (cupric ion reducing antioxidant capacity) method.
Abstract: It would be desirable to establish and standardize methods that can measure the total antioxidant capacity level directly from vegetable extracts containing phenolics. Antioxidant capacity assays may be broadly classified as electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The majority of HAT assays are kinetics-based, and involve a competitive reaction scheme in which antioxidant and substrate compete for peroxyl radicals thermally generated through the decomposition of azo compounds. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes colour when reduced. ET assays include the ABTS/TEAC, CUPRAC, DPPH, Folin-Ciocalteu and FRAP methods, each using different chromogenic redox reagents with different standard potentials. This review intends to offer a critical evaluation of existing antioxidant assays applied to phenolics, and reports the development by our research group of a simple and low-cost antioxidant capacity assay for dietary polyphenols, vitamins C and E, and human serum antioxidants, utilizing the copper(II)-neocuproine reagent as the chromogenic oxidizing agent, which we haved named the CUPRAC (cupric ion reducing antioxidant capacity) method. This method offers distinct advantages over other ET-based assays, namely the selection of working pH at physiological pH (as opposed to the Folin and FRAP methods, which work at alkaline and acidic pHs, respectively), applicability to both hydrophilic and lipophilic antioxidants (unlike Folin and DPPH), completion of the redox reactions for most common flavonoids (unlike FRAP), selective oxidation of antioxidant compounds without affecting sugars and citric acid commonly contained in foodstuffs and the capability to assay -SH bearing antioxidants (unlike FRAP). Other similar ET-based antioxidant assays that we have developed or modified for phenolics are the Fe(III)- and Ce(IV)-reducing capacity methods.
921 citations
Cites methods from "Use of a Free Radical Method to Eva..."
...A further disadvantage of DPPH is steric inaccessibility (i.e., small molecules may have a better chance to access the radical with subsequently higher TAC values) and narrow linear range of absorbance versus concentration [63]....
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...Mercimek (lentils) Ankara Flavans, Flavonols, Hydroxybenzoic Acids, Hydroxycinnamic Acids, Catechins, Flavones, Procyanidins, Resveratrol 2,2-diphenyl-1- picrylhydrazyl (DPPH) method For burns; roasted seeds are milled and applied on affected area [28a, 44] (Fabaceae) Phaseolus vulgaris L. Fasulye (beans, green) Ankara Isoflavonoid, Flavonols Folin-Ciocalteu method For wounds; ashes of the seeds are applied on wounds [28a, 45] (Poaceae) Hordeum vulgare L. Arpa (barley) Niğde Ankara Flavans , Flavones Folin-Ciocalteu method For abscesses; common cold and cough in pneumonia [28a] Molecules 2007, 12 1506 Proanthocyanidins: condensed tannins Flavonoids can exhibit their antioxidant activity (AO) in several ways [9]: (i) Radical scavenging activity toward either reactive species (e.g., reactive oxygen species: ROS) such as ....
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...Antioxidant activity assays existing in literature based on the measurement of radical scavenging activity of antioxidant compounds suffer from the difficulties encountered in the formation and stability of colored radicals [91] such as ABTS (2,2’-azinobis-(3-ethylbenzothiazoline6-sulfonic acid)) [73] and DPPH (2,2’-diphenyl-1-picrylhydrazyl) [77]....
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...(Vitaceae) Vitis vinifera L. Üzüm (grape) Niğde Anthocyanins, Flavonols, Flavones 1,1-Diphenyl-2- picrylhydrazyl (DPPH) radical scavenging method For bruises; pounded dry raisins are applied to bruises to relieve pain [28a, 39] Vegetables (Brassicaceae) Brassica oleracea L. Var....
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...Although the antioxidant activity of rosmarinic acid, another powerful antioxidant hydroxycinnamic acid, was reported to be much higher than those of Trolox® [121], α-tocopherol, caffeic acid, ferulic acid, BHT [122] and other plant phenolics [123], the ABTS/TEAC and DPPH methods applied by different researchers report low TEAC values within the interval of 1.5-2.0 for rosmarinic acid [124,125] while the CUPRAC method finds a TEAC value close to that of quercetin....
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References
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TL;DR: In this paper, the autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose.
Abstract: The autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose. Xanthan strongly inhibited the peroxidation of soybean oil containing tocopherols but showed no antioxidant activity on soybean oil without tocopherols in the emulsion. Xanthan did not have hydrogen donating ability but expressed Fe2+-binding activity. The Fe2+-binding activity corresponded to the pyruvate content of xanthan. Depyruvated xanthan did not inhibit effectively the autoxidation of soybean oil. The Fe2+-chelating structure of xanthan is discussed
2,919 citations
01 Jan 1990
TL;DR: The spontaneous reaction of atmospheric oxygen with organic compounds leads to a number of degradative changes that reduce the lifetime of many products of interest to the chemical industry, especially polymers, as well as causing the deterioration of lipids in foods.
Abstract: The spontaneous reaction of atmospheric oxygen with organic compounds leads to a number of degradative changes that reduce the lifetime of many products of interest to the chemical industry, especially polymers, as well as causing the deterioration of lipids in foods. The importance of oxygen in the deterioration of rubber was demonstrated over a century ago,1 and this finding led chemists to investigate the chemistry of oxidative deterioration and its inhibition.
1,059 citations
589 citations
TL;DR: This paper cites the paradoxical actions of antioxidants in processed foods and in living biological systems in the hope that these will lead the interested reader to further substantiation of the paradoxes cited.
Abstract: Scope of the Paper This paper cites the paradoxical actions of antioxidants in processed foods and in living biological systems. Essentially, it is a recognition of patterns of contradictory behavior. Limitations of space prevent detailed treatment of the paradoxes, their mechanistic basis, or citation of any more than one or two illustrative references. It is hoped that these will lead the interested reader to further substantiation of the paradoxes cited.
275 citations