COMPARATIVE STUDY ON THE PHENOLIC CONTENT, ANTIOXIDANT PROPERTIES AND HPLC FINGERPRINTING OF THREE VARIETIES OF CELOSIA SPECIES O.R. MOLEHIN 1,5 , S.A. ADEFEGHA 2 , G. OBOH 2 , J.A. SALIU 3,4 , M.L. ATHAYDE 4 and A.A. BOLIGON 4 1 Department of Biochemistry, Faculty of Science, Ekiti State University of Ado-Ekiti, Ado-Ekiti, P.M.B. 5363, Nigeria 2 Functional Food and Nutraceutical Unit, Department of Biochemistry, Federal University of Technology Akure, Akure, Nigeria 3 Department of Biochemistry, Adekunle Ajasin University, Ondo State, Nigeria 4 Departamento de Farmácia Industrial, Universidade Federal de Santa Maria, Santa Maria, Brazil 5 Corresponding author. TEL: +234-803-462-1267; EMAIL: molehin.olorunfemi@gmail.com Received for Publication February 22, 2014 Accepted for Publication July 29, 2014 doi:10.1111/jfbc.12090 ABSTRACT In this study, the phenolic content, characterization and antioxidant properties of aqueous extracts of three varieties of Celosia species were assessed. Celosia laxa had significantly (P < 0.05) higher total phenol and flavonoid contents than Celosia argentea (red variant) and Celosia argentea (green variant). Gallic acid, caffeic acid, quercetin and rutin were found in the three species of Celosia investi- gated. Rosmarinic acid and phenol glycoside were the two major compounds identified by high-performance liquid chromatography–diode-array detector in C. laxa, rutin and epigallocatechin were the prominent phenolics present in C. argentea (green variant) while C. argentea (red variant) had epigallocatechin as the most abundant phenolic compound. The extracts showed strong antioxidant actions as revealed by their 2,2-diphenyl-1-picrylhydrazyl radical, 2,2′-azinobis-3- ethylbenzo-thiazoline-6-sulfonate, nitric oxide radical-scavenging abilities and reducing power. These findings indicate that the aqueous extracts from Celosia species are potential sources of natural antioxidants. PRACTICAL APPLICATION Celosia laxa and Celosia argentea (green and red variants) are green leafy veg- etables commonly consumed as food and serve as important ingredients in tradi- tional medicine in Africa and Asia. The assessment of the antioxidant properties, phenolic content and composition of the three Celosia species may give insight into their applications in functional foods and nutraceuticals development. INTRODUCTION Production of reactive oxygen species such as hydroxyl radical ( . OH), superoxide (O2 -. ), hydrogen peroxide (H2O2) and singlet oxygen ( 1 O2) is linked to several degenerative diseases such as diabetes, cancer, cardiovascular diseases, Alzheimer’s disease and inflammation (Aruoma 1998; Valko et al. 2007; Roberts et al. 2009). Mounting data from epide- miologic studies have revealed that consumption of leafy vegetables was associated with reduced risk of these diseases (Hung et al. 2004; Oboh and Rocha 2007; Salas et al. 2010; Adefegha and Oboh 2011). Leafy vegetables are rich in anti- oxidant compounds such as vitamins C and E, β-carotene, flavonoids, tannins, and other phenolic constituents (Rice-Evans and Miller 1997; Karadeniz et al. 2005; Oboh et al. 2008). The human immune system is vulnerable to oxidative stress (Vider et al. 2001). During certain diseased states and aging, there is a need to boost antioxidant activities, thereby enhancing the immune mechanism (Victor et al. 2006; Valko et al. 2007; Pandey and Rizvi 2010). Free radicals and other reactive oxygen and nitrogen species are generated by all aerobic cells and are known to participate in several bio- logic and biochemical processes (Halliwell 1996). Moreover, overproduction of free radicals or depletion of antioxidants may cause oxidative stress through oxidation of biomolecules (Sporn and Suh 2000; Adefegha and Oboh 2012a). Oxidative stress is the main culprit of several Journal of Food Biochemistry ISSN 1745-4514 1 Journal of Food Biochemistry •• (2014) 1–9 © 2014 Wiley Periodicals, Inc.