Modified cupric reducing antioxidant capacity (CUPRAC) assay for measuring the antioxidant capacities of thiol-containing proteins in admixture with polyphenols

Çekiç, Sema Demirci; Başkan, Kevser Sözgen; Tütem, Esma; Apak, Reşat

doi:10.1016/j.talanta.2009.03.061

Cited by 51 publications

(31 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The Tris-glycine buffer with 8 M urea [37] contains also 4 mM citrate, therefore chelation of copper by the buffer components can also occur under the used experimental conditions [38]. Celic et al [34] refers that the use of this buffer is necessary to avoid the precipitation of the protein fraction of the sample, and add that the presence of 8 M urea partly denaturates proteins and significantly lowers the reduction potential of disulfide/thiol couples in peptides facilitating thiol oxidizability.…”

Section: Resultsmentioning

confidence: 99%

Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Marques

Magalhães

Tóth

et al. 2014

IJMS

View full text Add to dashboard Cite

Total antioxidant capacity assays are recognized as instrumental to establish antioxidant status of biological samples, however the varying experimental conditions result in conclusions that may not be transposable to other settings. After selection of the complexing agent, reagent addition order, buffer type and concentration, copper reducing assays were adapted to a high-throughput scheme and validated using model biological antioxidant compounds of ascorbic acid, Trolox (a soluble analogue of vitamin E), uric acid and glutathione. A critical comparison was made based on real samples including NIST-909c human serum certified sample, and five study samples. The validated method provided linear range up to 100 µM Trolox, (limit of detection 2.3 µM; limit of quantification 7.7 µM) with recovery results above 85% and precision <5%. The validated developed method with an increased sensitivity is a sound choice for assessment of TAC in serum samples.

show abstract

Section: Resultsmentioning

confidence: 99%

Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Marques

Magalhães

Tóth

et al. 2014

IJMS

View full text Add to dashboard Cite

show abstract

“…This method combines chromatographic separation, constituent analysis, and postcolumn identification of antioxidants in plant extracts [85]. CUPRAC in urea buffer also responded to thiol-containing proteins in food [86]. Another modified CUPRAC method is comprised of a tert-butylhydroquinone (TBHQ) probe with the phenazine methosulphate-β-nicotinamide adenine dinucleotide (PMS-NADH) non-enzymic O 2 •-generating system for superoxide radical scavenging activity (SRSA) assay of thiol-type antioxidants (e.g., GSH, cysteine), amino acids (e.g., serine, threonine), plasma antioxidants (e.g., bilirubin, albumin), and other antioxidants (e.g., methionine); the SRSA method is based on the measurement of the CUPRAC absorbance of the remaining TBHQ in the reaction medium (TBHQ is CUPRAC-reactive while its oxidation product is not, and this probe is isolated by ethyl acetate extraction from other CUPRAC-reactive interferents remaining in the aqueous phase) [87].…”

Section: Cuprac Assay As a Novel Et-based Antioxidant Capacity Assaymentioning

confidence: 99%

“…To determine the antioxidant properties of thiol-containing proteins, the modified CUPRAC method was adopted [86]. While the CUPRAC method is capable of determining all antioxidant compounds including thiols in complex sample matrices, the Ellman method of thiol quantitation basically does not respond to other antioxidants.…”

Section: Antioxidant Capacities Of Thiol-containing Proteinsmentioning

confidence: 99%

Methods of measurement and evaluation of natural antioxidant capacity/activity (IUPAC Technical Report)

Apak

Gorinstein

Böhm

et al. 2013

Pure and Applied Chemistry

Self Cite

487

374

View full text Add to dashboard Cite

Abstract:The chemical diversity of natural antioxidants (AOXs) makes it difficult to separate, detect, and quantify individual antioxidants from a complex food/biological matrix. Moreover, the total antioxidant power is often more meaningful to evaluate health beneficial effects because of the cooperative action of individual antioxidant species. Currently, there is no single antioxidant assay for food labeling because of the lack of standard quantification methods. Antioxidant assays may be broadly classified as the electron transfer (ET)-and hydrogen atom transfer (HAT)-based assays. The results obtained are hardly comparable because of the different mechanisms, redox potentials, pH and solvent dependencies, etc. of various assays. This project will aid the identification and quantification of properties and mutual effects of antioxidants, bring a more rational basis to the classification of antioxidant assays with their constraints and challenges, and make the results more comparable and understandable. In this regard, the task group members convey their own experiences in various methods of antioxidants measurement.

show abstract

“…The additivity of CUPRAC antioxidant capacities of thiol-containing proteins in admixture with polyphenols was previously shown by the authors’ laboratory [34]. The CUPRAC method has a rather straightforward chemistry toward polyphenols and thiols, oxidizing them to the corresponding quinones and disulfides, respectively, while converting its reagent (cupric-neocuproine) to the CUPRAC chromophore, cuprous-neocuproine complex.…”

Section: Discussionmentioning

confidence: 90%

Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins

Avan

Çekiç

Uzunboy

et al. 2016

IJMS

Self Cite

View full text Add to dashboard Cite

Development of easy, practical, and low-cost spectrophotometric methods is required for the selective determination of phenolic antioxidants in the presence of other similar substances. As electron transfer (ET)-based total antioxidant capacity (TAC) assays generally measure the reducing ability of antioxidant compounds, thiols and phenols cannot be differentiated since they are both responsive to the probe reagent. In this study, three of the most common TAC determination methods, namely cupric ion reducing antioxidant capacity (CUPRAC), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt/trolox equivalent antioxidant capacity (ABTS/TEAC), and ferric reducing antioxidant power (FRAP), were tested for the assay of phenolics in the presence of selected thiol and protein compounds. Although the FRAP method is almost non-responsive to thiol compounds individually, surprising overoxidations with large positive deviations from additivity were observed when using this method for (phenols + thiols) mixtures. Among the tested TAC methods, CUPRAC gave the most additive results for all studied (phenol + thiol) and (phenol + protein) mixtures with minimal relative error. As ABTS/TEAC and FRAP methods gave small and large deviations, respectively, from additivity of absorbances arising from these components in mixtures, mercury(II) compounds were added to stabilize the thiol components in the form of Hg(II)-thiol complexes so as to enable selective spectrophotometric determination of phenolic components. This error compensation was most efficient for the FRAP method in testing (thiols + phenols) mixtures.

show abstract

Modified cupric reducing antioxidant capacity (CUPRAC) assay for measuring the antioxidant capacities of thiol-containing proteins in admixture with polyphenols

Cited by 51 publications

References 27 publications

Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Methods of measurement and evaluation of natural antioxidant capacity/activity (IUPAC Technical Report)

Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins

Contact Info

Product

Resources

About