An antioxidant peptide derived from Ostrich (Struthio camelus) egg white protein hydrolysates Hamid Tanzadehpanah a , Ahmad Asoodeh b, c, ⁎, Jamshidkhan Chamani a a Department of Biology, Faculty of Sciences, Mashhad Branch, Islamic Azad University, Mashhad, Iran b Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran c Cellular and Molecular Research Group, Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran abstract article info Article history: Received 9 May 2012 Accepted 22 August 2012 Keywords: Ostrich egg white hydrolysates Antioxidant activity Bioactive peptide Mass spectrometry Ostrich (Struthio camelus) egg white (OEW) proteins were hydrolyzed using various proteases (α-chymotrypsin, pepsin, trypsin and papain). Antioxidant activities of hydrolysates were evaluated using 1, 1-diphenyl- 2-picrylhydrazyl (DPPH) radical scavenging and iron chelating activity. The hydrolysate obtained by trypsin exhibited the highest antioxidant activity. This hydrolysate was passed through an ultrafiltration membrane with a 3 kDa-cut off, and the resulting filtrate was purified using reversed-phase high performance liquid chromatography (RP-HPLC). Eight peptide fractions were separated and their antioxidant activities were tested. The results showed that the F 6 fraction possessed the highest antioxidant activity in the inhibition of linoleic acid autoxidation (86.4% at 20 μg/ml), scavenging activity for DPPH radical (81% at 200 μg/ml) and 2, 2-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) diammonium salt (ABTS) radical (37.6% at 90.9 μg/ml). In addition, the iron chelating activity, hydroxyl radical scavenging and reducing power of the F 6 fraction were 20% at 317.5 μg/ml, 28.6% at 163.9 μg/ml and 0.083 at 113.6 μg/ml, respectively. The peptide sequence was found to be LTEQESGVPVMK (with a molecular mass of 1317.65 Da) using mass spectrometry. The results suggest that the digestion of OEW proteins by trypsin protease could be exploited to produce natural antioxidants. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Reactive oxygen species (ROS) are the products of normal body reactions that have various forms, such as superoxide anion radicals (O 2 •) - , hydroxyl radicals (HO•), hydrogen dioxide (HO 2 •), hydrogen peroxide (H 2 O 2 ), and singlet oxygen (O 2 •)(Gülçin, 2009; Gülçin, Berashvili, & Gepdiremen, 2005). Among all oxygen species, superox- ide anion radical (O 2 •) - , hydroxyl radicals (HO•), and hydrogen per- oxide (H 2 O 2 ) are supposed to be the most abundant ROS in biological systems (Cui, Luo, Xu, & Murthy, 2004). ROS is one of the causes of cellular damages, destruction of protein structures and DNA muta- tions (Philanto, 2006). Effects of ROS on biomolecules can directly lead to toxic cellular reactions in the body. Furthermore, they are one of the major motives of health disorders, including cancer, arthri- tis, diabetes, inflammation, coronary heart disease and processes of aging (Bernardini et al., 2011). Thus, it is necessary to scavenge free radicals engendered in the living body and to inhibit the formation of free radicals by preventing the process of foodstuff oxidation. It was also reported that some synthetic antioxidative agents, such as butylatedhydroxyanisole (BHA), butylatedhydroxytoluene (BHT), propyl gallate and tert-butylhydroquinone (TBHQ) can be used in foods to suppress the formation of free radicals, preventing lipid- oxidation and improving shelf life (Wanita & Lorenz, 1996). However, the use of synthetic antioxidants affords potential risks to human health (Becker, 1993; Gülçin, 2012). In the past few years, biomaterials with antioxidant activity have drawn the attention of researchers. Bioactive peptides with antioxi- dant activity are a group of biomaterials that are derived from protein hydrolysates of various food sources; such as dairy, meat, soy and egg (Dávalos, Miguel, Bartolomé, & Lopez-Fandino, 2004). Some bioactive peptides derived from egg proteins have been described. Two bioac- tive peptides with the sequences of FRADHPFL and RADHPFL were identified after the enzymatic hydrolysis of hen egg white ovalbumin, exhibiting antihypertensive activity (Miguel & Aleixandre, 2006). Re- cently, we have reported an ACE inhibitory peptide, and antioxidant, antimicrobial peptide from hen egg white lysozyme hydrolysate (Asoodeh, Memarpoor-Yazdi, & Chamani, 2012; Memarpoor-Yazdi, Asoodeh, & Chamani, 2012). Ostrich egg whites are known as rich source of food proteins. In this study, protein hydrolysates from ostrich egg whites were prepared to extract antioxidant peptides. After purifying the antioxidant peptides using high performance liquid chromatography, the antioxidant activi- ties were measured via different methods, including autoxidation of linoleic acid, the scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2́ ́ ́́ -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) Food Research International 49 (2012) 105–111 ⁎ Corresponding author. Tel./fax: +98 5118795457. E-mail address: Asoodeh@um.ac.ir (A. Asoodeh). 0963-9969/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodres.2012.08.022 Contents lists available at SciVerse ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres