Introduction: The role and beneficial effects of antioxidants against various human diseases and food deterioration induced by oxidative stress have received much attention. The free radical scavenging antioxidants are one of the important classes of antioxidants and the assessment of their capacity has been the subject of extensive studies and argument. Various methods have been developed and applied in different systems, but many available methods result in inconsistent results. In this review article, the some available methods are critically reviewed on the basis of the mechanisms and procedure and pros and cons of the methods are proposed to assess the capacity of radical scavenging and inhibition of lipid peroxidation in vitro. Materials and Methods: The ABTS, DPPH, FRAP, ORAC, TRAO, CBA Fast BB, Folin-Ciocalteu and DSC assays were used to evaluate the comparability of the most common radical scavenging assays and achieve a wide range of technical principles of them. Results: Chemical-based methods are useful for assessment of antioxidant capacity, they are low cost, simple and yield an index value (expressed as equivalents of Trolox) that allows to compare the results. However, the antioxidant capacity indexes obtained by chemical assays cannot extrapolate the performance of the sample in vivo. Because some of the assays are done in non-physiological pH values, it is necessary to move to cellular assays in order to evaluate the potential antioxidant activity of a compound or extract. Animal models and human studies are more appropriate but also more expensive and time-consuming. Conclusion: At present, in spite of the diversity of methods, there is a great need to standardize the measurements of antioxidant activity. The consensus of opinion is that a mix of these tools should be used in assessing the antioxidant activities in vitro.
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