İnönü Üniversitesi, Eczacılık Fakültesi Analitik Kimya Anabilim Dalı, Malatya, Türkiye DOI : 10.12991/201317377 This article gives the information regarding mainly spectrophotometric methods that used to measure antioxidant activity. Ideally, the antioxidant activity should be tested using both in vitro and in vivo techniques but due to the high cost of in vivo testing, many products are evaluated by in vitro testing. On the basis of chemical reactions mechanism, major antioxidant capacity assays can be divided into two categories: hydrogen atom transfer (HAT) reaction based assay and single electron transfer (SET) reaction based assay. HAT-based assays include Oxygen Radical Absorbance Capacity (ORAC), Total Radical Trapping Antioxidant Paramater (TRAP) and Crocin Bleaching Assays. SET-based assays include the total phenols assay by Folin-Ciocalteu reagent (FCR), Trolox (6-hydroxy- 2,5,7,8-tetramethylchroman-2-carboxylic acid) equivalence antioxidant capacity (TEAC), ferric ion reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH) assay and total antioxidant potential assay using a Cu(II) complex as an oxidant (CUPRAC). Keywords : Antioxidant capacity, total phenolic content, hydrogen atom transfer reaction, electron transfer reaction