Modified DPPH and ABTS Assays to Assess the Antioxidant Profile of Untreated Oils Dionysios C. Christodouleas & Charalambos Fotakis & Aspasia Nikokavoura & Kyriakos Papadopoulos & Antony C. Calokerinos Received: 30 May 2014 /Accepted: 16 September 2014 # Springer Science+Business Media New York 2014 Abstract This research dwells on two widely used spectro- photometric methods, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, which assess the free radical scavenging activity (RSA) of natural samples and standard compounds. In particular, these assays were modified in order to simplify the evaluation of RSA of untreated edible oils, as well as to assess the antioxidant profile of oils’ hydrophilic and lipophil- ic extracts with the same analytical procedure. A thorough study highlighted the effect of solvents on the DPPH and ABTS methods and resulted in selecting 2-propanol and an ethanol/1-butanol solvent mixture as the reaction solvent for the DPPH method and the ABTS method, respectively. The developed methods were used to evaluate the RSA of 12 antioxidant compounds and 8 edible oils. Then, the contribu- tion of lipophilic and hydrophilic extracts to the total RSA of oils was estimated. The obtained results demonstrate the ap- plicability of the method to routine edible oil analysis. Keywords ABTS . DPPH . Reducing scavenging activity . Edible oils Introduction Antioxidant compounds are able to significantly suppress, delay, or prevent harmful oxidation processes, mainly caused by reactive oxygen species. They are characterized as high- ly health beneficial compounds, because they protect cells and macromolecules from oxidizing species, resulting in the prevention of diseases and the slowdown of aging (Gulcin 2012; Karadag et al. 2009; Tripoli et al. 2005; Covas et al. 2006). Antioxidants also affect and determine the shelf-life, nu- tritional value, and quality of the food products, as they can slow down the deterioration of food products during storage caused by oxidation processes. The concentration of antiox- idants in food samples can also be used as origin and fresh- ness indicators (Carocho and Ferreira 2013; Camilo and Denicol 2013). Many methods have been developed for the estimation of the antioxidant properties of natural products which can be classified into two main categories: (i) those based on the evaluation of the radical scavenging activity (RSA) of samples (i.e., 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfon- ic acid) (ABTS) assay, oxygen radical absorbance capacity (ORAC) assay, chemiluminescent assays) and (ii) those based on the evaluation of reducing activity of natural samples (i.e., ferric reducing/antioxidant power (FRAP) assay, cupric reduc- ing antioxidant capacity (CUPRAC) assay) (Antolovich et al. 2002; Sanchez-Moreno 2002; Laguerre et al. 2007; Roginsky and Lissi 2005). In general, the assays for the evaluation of antioxidant properties follow two prevalent mechanisms, the electron transfer (ΕΤ) and the hydrogen atom transfer (ΗΑΤ) reaction mechanism. The former includes the CUPRAC assay, DPPH assay, ABTS assay, FRAP assay, ferrous oxidation-xylenol orange (FOX) assay, ferric thiocyanate (FTC) assay, and aldehyde/carboxylic acid (ACA) assay (Moon and Electronic supplementary material The online version of this article (doi:10.1007/s12161-014-0005-6) contains supplementary material, which is available to authorized users. D. C. Christodouleas : C. Fotakis : A. C. Calokerinos (*) Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Athens, Greece e-mail: calokerinos@chem.uoa.gr D. C. Christodouleas : A. Nikokavoura : K. Papadopoulos Division of Physical Chemistry, IAMPPNM, NCSR Demokritos, Agia Paraskevi Attikis, 15310 Athens, Greece Food Anal. Methods DOI 10.1007/s12161-014-0005-6