www.elsevier.com/locate/bcdf Available online at www.sciencedirect.com Preparation of phosphorylated chitosan from gladius of the squid Sepioteuthis lessoniana (Lesson, 1830) and its in vitro antioxidant activity Namasivayam Subhapradha a , Pasiyappazham Ramasamy a , Sadhasivam Sudharsan a , Palaniappan Seedevi a , Meivelu Moovendhan a , Alagiri Srinivasan b , Vairamani Shanmugam a , Annaian Shanmugam a,n a CAS in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai 608502, Tamil Nadu, India b Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India article info Article history: Received 23 September 2012 Received in revised form 15 February 2013 Accepted 4 March 2013 Keywords: S. lessoniana Phosphorylated chitosan FT-IR Antioxidant Free radicals abstract To evaluate the antioxidant potential of phosphorylated chitosan from the Sepioteuthis lessoniana gladius that is thrown as waste in seafood processing industries. Chitin was extracted from the gladius of S. lessoniana by demineralization and deproteinization. Chitosan was obtained by deacetylation of chitin in strong alkali and phosphorylated by using ortho-phosphoric acid. The structure of phosphorylated chitosan was elucidated through Fourier Transform Infra Red (FT-IR) spectroscopy. The antioxidant efficacy of phosphorylated chitosan was assessed through scavenging activity against 2,2′-azinobis(3-ethylbenzothiazo- line-6-sulfonic acid diammonium salt) (ABTS), 1, 1-diphenyl-2-picrylhydrazyl (DPPH), super- oxide and hydroxyl radicals. The ability to chelate ferrous ion was also assessed. The yield and water solubility of phosphorylated chitosan was calculated as 81% and 78% respectively. The antioxidant activity of phosphorylated chitosan was found concentration dependent. The phosphorylated chitosan scavenges DPPH, ABTS, superoxide and hydroxyl radicals by 56.97%, 76.56%, 71.57% and 56.33% respectively and Inhibitory Concentration (IC 50 ) values of scavenging those radicals were reported as 4.53, 0.46, 0.38 and 0.5 mg/ml, respectively. The chelating ability of phosphorylated chitosan was 59.56% with IC 50 of 4.07 mg/ml. Moreover, the antioxidant activity of phosphorylated chitosan was compared with that of the standards such as Butylated Hydroxy Anisole (BHA), ascorbic acid, α-Tocopherol and Ethylene Diamine Tetra Acetic acid (EDTA). The results of the present investigation suggest that the phosphorylated chitosan with potent antioxidant property could be used as an alternative antioxidant that from a natural non-conventional source. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen peroxide, hydroxyl radical and superoxide anion called reactive oxygen species (ROS) are generated during normal metabolism and oxidize biomolecules such as lipids, proteins, carbohydrates and DNA, ultimately leading to oxi- dative stress. However, cells produce antioxidants such as catalase, superoxide dismutase, glutathione peroxidase and thioredoxins as a part of the cellular defense system against ROS-mediated cellular injury (Rahman, Biswas, & Kode, 2006). 2212-6198/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bcdf.2013.03.001 n Corresponding author. Tel.: þ91 9443043597. E-mail addresses: shanpappu48@gmail.com, shanpappu@yahoo.com (A. Shanmugam). Bioactive CarbohydratesandDietary Fibre 1 (2013) 148–155