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Molecules 2015, 20(12), 22411-22421; doi:10.3390/molecules201219855

A Comprehensive Study of the Use of Cu(I)/4,4’-Dicarboxy-2,2’-biquinoline Complexes to Measure the Total Reducing Capacity: Application in Herbal Extracts

CEPES (Centro de Estudos, Pesquisa, Prevenção e Tratamento em Saúde), Faculdade de Medicina da Fundação do ABC, Av. Príncipe de Gales 821, Santo André 09060-650, Brazil
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Author to whom correspondence should be addressed.
Academic Editor: David D. Kitts
Received: 26 September 2015 / Revised: 20 November 2015 / Accepted: 8 December 2015 / Published: 14 December 2015
(This article belongs to the Special Issue Antioxidants—A Risk-Benefit Analysis for Health)
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Abstract

A method for the determination of total reducing capacity (TRC) based on the reduction of Cu(II) to Cu(I) by antioxidants in a buffered solution (pH 7.0) containing 4,4′-dicarboxy-2,2′-biquinoline acid (BCA) was developed. Absorbance values at 558 nm characteristic of the Cu(I)/BCA complexes formed were used to determine the TRC of aqueous extracts of twelve Brazilian plants. The TRC values obtained with the suggested method correlated well with values obtained using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method (r2 = 0.959). They were also compared with the total polyphenol content (using the Folin-Ciocalteu reagent) and the good agreement (r2 = 0.919) indicates that the polyphenols should be responsible for this reducing capacity. The method proposed here (and successfully applied in plant extracts) can be used to measure the TRC of aqueous samples derived from other plants (e.g., teas, juices, beers and wines) and even in biological samples (e.g., serum, urine and follicular fluid). To achieve a structure-activity relationship of the proposed reaction, the reduction capability of 25 standard antioxidants (phenolic derivatives, flavonoids, stilbenoids, vitamins, etc.) was individually evaluated and the apparent molar absorptivity values (at 558 nm) obtained were compared and discussed. View Full-Text
Keywords: 4,4′-dicarboxy-2,2′-biquinoline acid; Cu(II); total reducing capacity; Brazilian medicinal plants 4,4′-dicarboxy-2,2′-biquinoline acid; Cu(II); total reducing capacity; Brazilian medicinal plants
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Manoel, H.R.; Moya, H.D. A Comprehensive Study of the Use of Cu(I)/4,4’-Dicarboxy-2,2’-biquinoline Complexes to Measure the Total Reducing Capacity: Application in Herbal Extracts. Molecules 2015, 20, 22411-22421.

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