Antioxidant activity of three polyphenol-enriched cocoa products obtained on an industrial scale

Abstract

Using different protocols we have obtained three cocoa extracts with a high content in polyphenols: A (167mg/g), B (374mg/g) and C (787mg/g). The scavenging capacity of the extracts was measured as the ability to bleach the stable radicals DPPH· and ABTS·+, and the antioxidant effect of them by the FRAP assay [1]. The results in the DPPH test were 0.2, 1.4 and 3.0 (expressed as Trolox equivalent, µmol/mg dry weight of each extract), and in the ABTS test were 1.0, 4.7 and 9.8, for A, B and C, respectively. The antioxidant capacity expressed as ascorbic acid equivalent were 17.2, 76.1 and 207.7, respectively. The scavenging properties of cocoa powder against the superoxide anion, H2O2, HClO [1], and peroxynitrite [2] were determined and the IC50 (µg/mL) values were 77.5, 12.3 and 10.3, for A, B and C, respectively, in the hypoxanthine/xanthine oxidase test, and 225.4, 73.2 and 21.5 as HOCl scavenger, respectively. Only extract C gave relevant effect as scavenger of peroxynitrite anion, with IC50 (µg/mL) of 76.1 and 110.0 in absence or presence of bicarbonate. None of the tested extract was active in the hydrogen peroxide test, but B and C significantly increased the deoxyribose degradation in the absence of ascorbate. None of the extracts inhibited the ferrous or copper chelating activity at 100µg/mL, but they inhibited the lipid peroxidation in brain homogenates and human plasma using non-enzymatic generation systems [3], giving the extract C the best IC50 (µg/mL) values, 17.4 and 8.1 against to lipid peroxidation in brain homogenates and human plasma, respectively. We conclude that cocoa may constitute a source of polyphenols which could serve for enriching foods, nutraceuticals and alimentary supplements.