The determination of total concentration and activity of antioxidants in foodstuffs

Abstract

We developed a new method for the analysis of active antioxidants that is based on their reactions with the ABTS+. cation radical obtained by oxidation of ABTS, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt. The feasibility of this method was confirmed by electrochemical and kinetic studies of model antioxidants. ABTS+. was shown to react rapidly with active and slowly with weak antioxidants, which allows it to be used as a model radical for the quantitative determination of the total content of natural antioxidants (antioxidant equivalent) in natural extracts and wines. Another analytical method based on the competitive oxidation of Pyrogallol Red (a detecting molecule) and the examined antioxidants by radicals derived from peroxynitrite was used for measuring the relative activity of antioxidants. A combination of both methods helped measure the total concentration of antioxidants and their average specific activities (per molecule of active compound) in extracts from grape, olive, and tomato and concentrates of various popular beverages (wines, beers, and juices), as well as in the commercial concentrated food product Kréto-A, made from grape, red wine, tomato, and olive. Red wine and red grape juice were shown to be the most rich in antioxidants (up to 20 mM), with their activity being similar to that of polyphenols. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 6; see also http://www.maik.ru.