Exploring the relation between composition of extracts of healthy foods and their antioxidant capacities determined by electrochemical and spectrophotometrical methods

The antioxidant capacity of the extracts (in trolox equivalents) was measured by using the DPPH radical scavenging assay, CUPRAC assay and two electrochemical methods implying radicals generated from hydrogen peroxide on Hg and glassy carbon electrodes covered with Pt nanoparticles and poly-neutral red (PNR-Pt). There are good correlations between the antioxidant capacities measured by the two electrochemical techniques and also between such techniques and CUPRAC, but the DPPH radical scavenging assay measures different type of antioxidant activity than the rest. The relation between antioxidant capacity and composition from the viewpoint of concentration and individual antioxidant capacity of each component is discussed. The main conclusion indicates that the total content of antioxidants of an extract is not bi-univocally related to its antioxidant capacity, because the distinct components of the extracts can have very different antioxidant capacities.