مرکز منطقه ای اطلاع رساني علوم و فناوري - The assays used for assessing antioxidant capacities of herbal products and foods

Abstract :

In this study, the assays used for antioxidant capacity of herbal products and foods were described comparatively each other. Various assays have been used to evaluation of antioxidant capacity of herbal products and foods. These assays should be classified into two types: assays based on hydrogen atom transfer (HAT) reactions and assays based on electron transfer (ET). HAT based assays include oxygen radical absorbance capacity (ORAC), total radical trapping antioxidant parameter (TRAP), and crocin bleaching assays. ET-based assays include the total phenols assay by Folin-Ciocalteu reagent (FCR), Trolox equivalence antioxidant capacity (TEAC), ferric ion reducing antioxidant power (FRAP), “total antioxidant potential” assay using a Cu (II) complex as an oxidant, and DPPH assay. Electron transfer assays measure the reducing ability of the substrate (antioxidant) while hydrogen atom transfer assays measure the hydrogen donating ability of the substrate. It is clear that hydrogen atom donation is essential in the radical chain reaction stage of lipid peroxidation, therefore hydrogen transfer assays are relevant to the measurement of chain-breaking antioxidant capacity. In many cases, the antioxidant capacity or the ability to trap radicals, of a compound is related to the ease of hydrogen atom donation, not necessarily the redox potential of the compound. In general, assays that measure hydrogen atom transfer would be preferable to assays that measure electron transfer reactions. In the study, the use of multiple electron transfer assays is redundant. There are correlations between them, because these assays rely on the same redox reactions. When the assays measure reducing ability were used it is important to choose one that is widely reported and validated. Similarly, the ORAC assay between assays that measure hydrogen atom transfer has been extensively validated, reliable and provides useful information about the radical chain-breaking capacity of the sample.