Advantages and pitfalls of the methods for the antioxidant activity evaluation

The beneficial influence on human health of many foodstuffs and beverages originates from their antioxidant activity. The increasing interest on the role of natural antioxidants in biological systems and their nutritional effects has determined continuous efforts in the search of simple and reliable methods for the determination of antioxidant activity. In this paper an overview of the most used methodologies for the determination of antioxidant capacity is presented, placing particular emphasis on the advantages, the pitfalls and the possible developments of each method. In particular the methods based on the Electron Spin Resonance (ESR) spectroscopy with direct measurement of relatively stable radical species or unstable radicals, trapped to form stable adducts (spin trapping method), are reviewed and compared with assays based on spectrophotometric and voltammetric methods. All of these methods, widely used in the food industry, differ for the antioxidant mechanism involved, the analytical conditions applied in terms of substrate, solvents and range of concentrations, the instrumentation used and the outcome they provide. This review thus focuses on the effect of each analytical parameter on the antioxidant activity evaluation. When selecting an appropriate method for the estimation of the antioxidant activity, any interference should be known in advance. In addition an overall evaluation of the antioxidant activity should be based on a comparison of different methods in order to overcome the limitations of the method itself. Hence this review provides a basis for the choice of the best antioxidant activity method applicable to a particular nutraceutical or dietary supplement in a particular matrix.