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Novel pro-oxidant activity assay for polyphenols, vitamins C and E using a modified CUPRAC method.
Talanta. 2013 Oct 15; 115:583-9.T

Abstract

In this study, a direct assay, a modified CUPRAC (Cupric Ion Reducing Antioxidant Capacity) method, is developed to determine transition metal ion (Cu(II))-catalyzed pro-oxidant activity of polyphenolic compounds, vitamins C and E, and herbal samples in the presence of proteins containing thiol groups. Since transition metal ion-catalyzed pro-oxidant activity of phenolics is usually initiated with the reduction of the metal to lower oxidation states (as a prerequisite of Fenton-type reactions), this method involves the reduction of copper(II) ions to copper(I) by polyphenolic compounds (simultaneously giving rise to reactive species), binding of the formed Cu(I) to egg white protein -SH groups, and liberation of copper(I)-neocuproine (Cu(I)-Nc) chelate (showing maximum absorbance at 450 nm) by treating the incubation product with a neocuproine-ammonium acetate mixture. The proposed method is validated against atomic absorption spectrometric (AAS) determination of protein-bound copper and protein carbonyl assay of oxidative stress. The proposed assay is faster and more specific than the carbonyl assay, and uses low-cost reagents and equipment. Pro-oxidant activity (i.e. proportional to absorbance) varies linearly over a relatively wide range with concentration, as opposed to the reciprocal correlations (i.e. linear regression of 1/(pro-oxidant activity) versus 1/concentration) of other similar assays. The pro-oxidant activity order of the tested antioxidant compounds in terms of 'Quercetin Equivalent Pro-oxidant Activity' (QREPA) coefficients is: gallic acid > epicatechin > quercetin ≈ catechin > α-tocopherol > rosmarinic acid > trolox > caffeic acid > ascorbic acid.

Authors+Show Affiliations

Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar 34320, Istanbul, Turkey.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

24054636

Citation

Kondakçı, Esin, et al. "Novel Pro-oxidant Activity Assay for Polyphenols, Vitamins C and E Using a Modified CUPRAC Method." Talanta, vol. 115, 2013, pp. 583-9.
Kondakçı E, Özyürek M, Güçlü K, et al. Novel pro-oxidant activity assay for polyphenols, vitamins C and E using a modified CUPRAC method. Talanta. 2013;115:583-9.
Kondakçı, E., Özyürek, M., Güçlü, K., & Apak, R. (2013). Novel pro-oxidant activity assay for polyphenols, vitamins C and E using a modified CUPRAC method. Talanta, 115, 583-9. https://doi.org/10.1016/j.talanta.2013.06.006
Kondakçı E, et al. Novel Pro-oxidant Activity Assay for Polyphenols, Vitamins C and E Using a Modified CUPRAC Method. Talanta. 2013 Oct 15;115:583-9. PubMed PMID: 24054636.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Novel pro-oxidant activity assay for polyphenols, vitamins C and E using a modified CUPRAC method. AU - Kondakçı,Esin, AU - Özyürek,Mustafa, AU - Güçlü,Kubilay, AU - Apak,Reşat, Y1 - 2013/06/13/ PY - 2013/04/01/received PY - 2013/06/01/revised PY - 2013/06/06/accepted PY - 2013/9/24/entrez PY - 2013/9/24/pubmed PY - 2014/4/16/medline KW - Modified CUPRAC method KW - Polyphenolic compounds KW - Pro-oxidant activity KW - Protein oxidation SP - 583 EP - 9 JF - Talanta JO - Talanta VL - 115 N2 - In this study, a direct assay, a modified CUPRAC (Cupric Ion Reducing Antioxidant Capacity) method, is developed to determine transition metal ion (Cu(II))-catalyzed pro-oxidant activity of polyphenolic compounds, vitamins C and E, and herbal samples in the presence of proteins containing thiol groups. Since transition metal ion-catalyzed pro-oxidant activity of phenolics is usually initiated with the reduction of the metal to lower oxidation states (as a prerequisite of Fenton-type reactions), this method involves the reduction of copper(II) ions to copper(I) by polyphenolic compounds (simultaneously giving rise to reactive species), binding of the formed Cu(I) to egg white protein -SH groups, and liberation of copper(I)-neocuproine (Cu(I)-Nc) chelate (showing maximum absorbance at 450 nm) by treating the incubation product with a neocuproine-ammonium acetate mixture. The proposed method is validated against atomic absorption spectrometric (AAS) determination of protein-bound copper and protein carbonyl assay of oxidative stress. The proposed assay is faster and more specific than the carbonyl assay, and uses low-cost reagents and equipment. Pro-oxidant activity (i.e. proportional to absorbance) varies linearly over a relatively wide range with concentration, as opposed to the reciprocal correlations (i.e. linear regression of 1/(pro-oxidant activity) versus 1/concentration) of other similar assays. The pro-oxidant activity order of the tested antioxidant compounds in terms of 'Quercetin Equivalent Pro-oxidant Activity' (QREPA) coefficients is: gallic acid > epicatechin > quercetin ≈ catechin > α-tocopherol > rosmarinic acid > trolox > caffeic acid > ascorbic acid. SN - 1873-3573 UR - https://www.unboundmedicine.com/medline/citation/24054636/Novel_pro_oxidant_activity_assay_for_polyphenols_vitamins_C_and_E_using_a_modified_CUPRAC_method_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0039-9140(13)00506-7 DB - PRIME DP - Unbound Medicine ER -