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.

• Grant number: 15/26382-2
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: May 01, 2016
• End date: October 31, 2016
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
• Principal Investigator: Horacio Dorigan Moya
• Grantee: Horacio Dorigan Moya
• Host Institution: Faculdade de Medicina do ABC (FMABC). Organização Social de Saúde. Fundação do ABC. Santo André , SP, Brazil

Abstract

A method for the determination of total reducing capacity (TRC) based on the reduction reaction of Cu(II) to Cu(I) by antioxidants in buffered solution (pH 7.0) containing the 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 were compared with the values using with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method showing excellent correlation (r2 = 0.959). They were also compared with the total polyphenol content (using the Folin-Ciocalteu reagent) and the great agreement (r2 = 0.919) indicates that the polyphenols should be responsible for this reducing capacity. The method proposed here (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). As an attempt to better understand this reaction the reduction capability of 25 standard antioxidants compounds (phenolic derivatives, flavonoids, stilbenoids, vitamins, etc.) was evaluated individually and the apparent molar absorptivities values (at 558 nm) obtained were discussed considering the molecular structure of each antioxidant. (AU)