Analytical Tools for the Determination of Antioxidants and Antioxidant Capacity in Biological Samples, Principles and Applications

Background: There are two types of antioxidants -high molecular weight antioxidants like glutathione peroxidase and superoxide dismutase and low molecular weight antioxidants like ascorbic acid, glutathione, uric acid, melatonin. Both types of antioxidants are necessary in the system keeping oxidative homeostasis and protecting against reactive oxygen and nitrogen species. Objective: This review is focused on low molecular weight antioxidant assay which can serve as an important tool for various diagnoses since the antioxidant level corresponds with pathological states and can indicate oxidative stress. The assay of antioxidants is also a tool for food quality control because the antioxidant level is decreasing due to aging and poor storage conditions. Disparate protocols were established in order to judge antioxidant capacity. Conclusion: In this review, spectrophotometric tests like 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) based assay (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), like ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), electrochemical assays and instrumental analyses are described and discussed. Survey of actual literature and principle of the analyses are provided as well.