Carbohydrate Polymers 99 (2014) 624–629 Contents lists available at ScienceDirect Carbohydrate Polymers jo u r n al homep age: www.elsevier.com/locate/carbpol Sulphation can enhance the antioxidant activity of polysaccharides produced by Enterobacter cloacae Z0206 Mingliang Jin a,b , Youming Wang a , Ming Huang a , Zeqing Lu a , Yizhen Wang a,∗ a Key Laboratory of Molecular Animal Nutrition of Ministry of Education, College of Animal Sciences, Zhejiang University, No. 866 Yuhangtang Road, Hangzhou 310058, PR China b School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, PR China a r t i c l e i n f o Article history: Received 13 May 2013 Received in revised form 17 August 2013 Accepted 23 August 2013 Available online 2 September 2013 Keywords: Sulfated polysaccharides Enterobacter cloacae Antioxidant RAW264.7 Apoptosis a b s t r a c t The protective effects of sulfated polysaccharide derivatives produced by Enterobacter cloacae Z0206 against H 2 O 2 -induced oxidative damage in RAW264.7 murine macrophages as well as the possible mech- anisms governing the protective effects were studied. Sulfated polysaccharides protected RAW264.7 cells from oxidative damage and apoptosis induced by H 2 O 2 by protecting the cellular structure; improving the activity of antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px); and inhibiting caspase-3 activation and DNA fragmentation. In addition, the sulfated polysac- charides conferred higher levels of protection from H 2 O 2 -induced oxidative damage in RAW264.7 murine macrophages compared to the native polysaccharide lacking sulfation. These results indicated that sul- fated modifications might be an effective approach to enhance the antioxidant activity of polysaccharides produced by E. cloacae Z0206, and the sulfated derivatives of these polysaccharides may act as potent antioxidant agents. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction The uncontrolled generation of free radicals and reactive oxy- gen species (ROS) is involved in the pathogenesis of more than 50 human diseases, such as cancer, diabetes, aging, and atheroscle- rosis (Jin, Zhao, Huang, Xu, & Shang, 2012b; Moskovitz, Yim, & Chock, 2002). Antioxidants can protect the cells in the body from free radicals and ROS and can prevent the oxidation of biomacro- molecules, including DNA, membrane lipids and proteins (Cho, Kim, Ahn, & Je, 2011). Some synthetic antioxidants have been developed and extensively used, including butylated hydroxytoluene and butylated hydroxyanisole (Krishnaiah, Sarbatly, & Nithyanandam, 2011). However, these synthetic agents have certain drawbacks, including adverse side effects, which may cause liver damage and carcinogenesis (Krishnaiah, Sarbatly, & Bono, 2007). Therefore, there has recently been increased interest in the exploration of safer and more effective naturally occurring antioxidants to inhibit oxidative damage (Zhao et al., 2012). Polysaccharides are a group of naturally occurring macro- molecules present in many organisms (Wang et al., 2010b) that have been extensively studied in medicine due to their various biological activities (Jin, Lu, Huang, Wang, & Wang, 2012a). In ∗ Corresponding author. Tel.: +86 571 88982815; fax: +86 571 88982650. E-mail addresses: yzwang@zju.edu.cn, yzwang321@zju.edu.cn (Y. Wang). particular, polysaccharides have recently received considerable attention due to their function as antioxidants (Chen, Ma, Liu, Liao, & Zhao, 2012; Ye & Huang, 2012). The biological activity of polysaccharides might be enhanced by chemical modifications and structural improvements (Liu et al., 2009; Wang et al., 2010a). Sul- fated polysaccharides are polysaccharides in which the hydroxyl groups are partially replaced by sulfate groups, and they possess different or stronger biological activity compared to non-sulfated polysaccharides (Jin, Lu, Huang, Wang, & Wang, 2011; Wang et al., 2010b). Many studies have demonstrated that the antioxidant activity of polysaccharides is strikingly improved by sulfated modi- fication (Wang et al., 2010a; Zhang et al., 2011). Therefore, sulfated modification may be used to improve the antioxidant activity of some polysaccharides and to generate naturally occurring antioxi- dants. The bacterial strain Enterobacter cloacae Z0206 can produce large amounts of exopolysaccharides. In our previous study, we extracted and purified the major exopolysaccharide (EPS) produced by E. cloacae Z0206 (Jin et al., 2010). The structural analysis indi- cated that the EPS is composed of l-fucose, d-glucose, d-galactose, d-glucuronic acid and pyruvic acid in the approximate molar ratio of 2:1:3:1:1 with an average molecular weight of approximately 1.1 × 10 6 Da. A combination of chemical analysis coupled with electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy showed that the EPS comprises a hep- tasaccharide repeating unit (Wang, Yang, & Wang, 2013). The administration of EPS at the dose of 200 mg/kg body weight to 0144-8617/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2013.08.072