Original article Antioxidant capacity of fresh, sun- and sulphited-dried Malatya apricot (Prunus armeniaca) assayed by CUPRAC, ABTS/TEAC and folin methods Kubilay Gu ¨c ¸lu ¨ , Mehmet Altun, Mustafa O ¨ zyu ¨ rek, Saliha E. Karademir & Resat Apak* Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar 34320, Istanbul, Turkey (Received 4 May 2005; Accepted in revised form 6 January 2006) Summary Apricots as five varieties of Malatya region have been assayed as fresh, sun- and sulphited-dried samples, using the antioxidant capacity measurement methods Cupric Ion Reducing Antioxidant Capacity (CUPRAC) and 2,2¢-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and total polyphenol measurement method Folin. The novel reagent for the CUPRAC total antioxidant capacity assay, bis(neocuproine)copper(II) chloride, was easily accessible, stable, selective and responding to all antioxi- dants. Sulphite (normally contributing to the colour formed in the CUPRAC assay) was removed prior to assay on a strongly basic anion exchanger at pH 3 in the form of HSO  3 . The CUPRAC findings correlated well with the results of ABTS/TEAC and Folin assays (r ¼ 0.93), all being electron-transfer-based antioxidant capacity assays. The calibration lines of pure flavonoids individually and in standard-added apricot extracts were parallel, indicating the additivity of absorbances in CUPRAC. This work reports for the first time the use of a novel spectrophotometric method (CUPRAC) for the assay of both total antioxidant capacity and sulphite levels of diverse apricot samples. Keywords ABTS assay, antioxidant capacity, apricot (Prunus armeniaca), CUPRAC assay, folin assay, polyphenolic content, sulphite. Introduction When natural antioxidant defences of the organism (of enzymatic, non-enzymatic or dietary origin) are over- whelmed by an excessive generation of reactive oxygen species, a situation of oxidative stress occurs, in which cellular and extracellular macromolecules (proteins, lipids and nucleic acids) can suffer oxidative damage, causing the tissue injury (Halliwell & Gutteridge, 1989; Halliwell & Aruoma, 1991). Consumption of foods naturally bearing antioxidant activity (e.g. fruits and vegetables) is the most efficient way of combating such tissue injuries, undesired transformations and health risks. It is noteworthy that in many studies about plant antioxidant research, it has been clearly indicated that the measured antioxidant activity is too dependent on the type of assay selected (Dorman et al., 2003; Trou- illas et al., 2003; Miliauskas et al., 2004), and that the observed antioxidant activity (or capacity) is not fully correlated to total polyphenolics content of the plant extracts (Kahkonen et al., 1999; Dorman et al., 2003; Miliauskas et al., 2004), the linear correlation coeffi- cients either between two given antioxidant activity assays or between antioxidant capacity and polyphen- olics content of herbal extracts not being as close to 1 as expected. However, electron transfer-based antioxidant capacity assays involving one redox reaction with the oxidant (also the probe for monitoring the reaction) as an indicator of the reaction end-point: Probe (oxidant) þ e  (from antioxidant) ! reduced probe þ oxidised antioxidant where the change in colour of the probe is proportional to the total antioxidants concentration, may yield results that show good correlations among themselves (Huang et al., 2005). In this regard, Folin (FCR), ABTS/TEAC, FRAP and DPPH assays are all classified as electron- transfer assays, and it is emphasised that the reaction rate differences between antioxidants and oxidants are not reflected in the ABTS/TEAC values because the TEAC assay is an end-point assay (Huang et al., 2005). The diverse antioxidant activity/capacity assay methods existing in literature depending on the consumption of chromogenic radicals, i.e. ABTS (Miller et al., 1993) and *Correspondent: Fax: +90-212-473 7180; e-mail: rapak@istanbul.edu.tr International Journal of Food Science and Technology 2006, 41 (Supplement 1), 76–85 76 doi:10.1111/j.1365-2621.2006.01347.x Ó 2006 Institute of Food Science and Technology Trust Fund