Comparative evaluation of various total antioxidant capacity assays applied to phenolic compounds with the CUPRAC assay.

By Resat Apak, K. Güçlü, B. Demirata, Mustafa Özyürek, Saliha Esin Çelik, Burcu Bektaşoğlu, K. Berker, D. Ozyurt. Molecules, 2007

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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.

Subfields: Biochemistry, Organic Chemistry

View Paper: https://www.semanticscholar.org/paper/a3140ab0a85546a576b3bf379b14fab6891c1390

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Citations in the corpus

Review of Methods to Determine Antioxidant Capacities (2009, methodology): “Another shortcoming of TRAP assay is the use of the lag time that corresponds to the inhibition of accumulation of colored radical reagents in the presence of antioxidants (e.g., the time period required for the colored radical to emerge in the reaction medium; Apak et al. 2007) for quantifying anti”
Natural Antioxidants in Foods and Medicinal Plants: Extraction, Assessment and Resources (2017, methodology): “As one of the few stable organic nitrogen radicals, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical is used to analyze the antioxidant activity [151,155].”
Antioxidants in wild mushrooms. (2009, background): “Phenolic compounds are aromatic hydroxylated compounds, possessing one or more aromatic rings with one or more hydroxyl groups, being commonly found in vegetables, fruits and many food sources that form a significant portion of our diet, and some of which are among the most potent and therapeuticall”
Flavonoids and phenolic acids: Role and biochemical activity in plants and human (2011, background): “Natural or phytochemical antioxidants are secondary metabolites in plants (Dai and Mumper, 2010) such as phenolic acids, flavonoids and carotenoids, which are amongst the antioxidants produced by plants for their sustenance (Apak et al., 2007).”