Determination of Total Antioxidant Capacity of Lipophilic and Hydrophilic Antioxidants In the Same Solution by Using Fer
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Determination of Total Antioxidant Capacity of Lipophilic and Hydrophilic Antioxidants In the Same Solution by Using Ferric–Ferricyanide Assay Kadriye Işıl Berker & Birsen Demirata & Reşat Apak
Received: 17 October 2011 / Accepted: 20 December 2011 / Published online: 12 January 2012 # Springer Science+Business Media, LLC 2012
Abstract The purpose of this work is to develop a simple, low-cost, and diversely applicable antioxidant capacity assay, the ferric–ferricyanide method based on Prussian blue formation, for both lipophilic and hydrophilic antioxidants in food matrices. The trolox equivalent antioxidant capacities of various antioxidant compounds were calculated with respect to the ferric–ferricyanide, FRAP, and modified CUPRAC methods. The linear calibration curves of the ferric–ferricyanide assay for lipophilic antioxidants (as absorbance vs. concentration) in 1:9 (v/v) H2O–acetone mixture solution with and without 2% MβCD were comparatively drawn. Simultaneous determination of lipophilic and hydrophilic antioxidants could be achieved without using MβCD. Testing of synthetic mixtures of lipophilic and hydrophilic antioxidants in 1:9 (v/v) H2O– acetone medium with the proposed method yielded the theoretically expected antioxidant capacities, considering the additivity of absorbances of constituents obeying Beer’s law. The proposed assay is simple, versatile, and cost-effective; its reagents are cheap and stable, and can be performed using a simple colorimeter. Keywords Total antioxidant capacity . Fe(III) reducing power . Lipophilic antioxidants . Hydrophilic antioxidants . Ferricyanide/Prussian blue assay K. I. Berker : B. Demirata Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, Ayazaga Maslak, 34469 Istanbul, Turkey R. Apak (*) Department of Chemistry, Istanbul University, Faculty of Engineering, Avcilar, 34320 Istanbul, Turkey e-mail: [email protected]
Introduction Antioxidants are important health beneficial compounds that react with an excess of reactive oxygen and nitrogen species under “oxidative stress” conditions, thereby preventing related diseases such as cell aging, cardiovascular and neurodegenerative diseases, and cancer (Halliwell and Gutteridge 1989; Halliwell and Aruoma 1991). It is very important to measure the total antioxidant capacity (TAC) level directly from vegetable samples. TAC assays can be broadly classified as electron transfer (ET)- and hydrogen atom transfer (HAT)-based methods. ET-based assays involve a redox reaction of antioxidants with oxidant probes, acting as an indicator of the reaction endpoint through absorbance or fluorescence changes. HATbased assays, exemplified by oxygen radical absorbance capacity (ORAC) assay (Cao et al. 1995), apply a competitive reaction scheme in which antioxidant and substrate kinetically compete for thermally generated peroxyl radicals through the decomposition of azo compounds such as ABAP (2,2′-azobis(2-aminopropane) dihydrochloride) (Huang et al. 2005; Prior et al. 2005; Celik et al. 2007). ET-b
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