preparation, characterization, and antioxidant properties of gallic

Carbohydra te Polymers 83 (2011) 1617–162 2 Contents lists available at ScienceDirect Carbo hy drate Pol ymers j ou r n a l home p a g e: www.elsevier.com/locate/carbpol Preparation, characterization, and antioxidant properties of gallic acid- grafted-chitosans Young-Sook Cho a , Se-Kwon Kim a , Chang-Bum Ahn b , Jae-Young Je b,∗ a Department of Chemistry and Marine Bioprocess Research Center, Pukyong National University, Busan 608-737, Republic of Korea b School of Food Technology and Nutrition, Chonnam National University, Yeosu 550-749, Republic of Korea a r t i c l e i n f o Article history: Received 17 September 2010 Received in revised form 7 October 2010 Accepted 7 October 2010 Available online 15 October 2010 Keywords: Chitosan Gallic acid Antioxidant Free radical ROS a b s t r a c t Galli c acid- grafted-chitosans (GA- g -chitosan s) wit h four dif fer ent gra fti ng rat ios wer e prepar ed by a free radical-induced grafting reaction in order to improve antioxidant and water-solubility. To verify the synthesis of GA- g -chitosans, 1 H NMR and thin layer chromatography were employed, and the results revealed that GA was grafted onto the chitosan. The antioxidant properties of the GA- g -chitosans were evaluated using several in vitro models. GA- g -chitosan (I), which has the highest GA content, showed 92.26% scavenging activity against 2,2-diphenyl-1-picrylhydrazyl and 93.15% hydrogen peroxide scavenging activity at 50 g/mL. GA- g -chitosan (I) was also showed higher reducing power compared to others. All GA- g -chitosans showed improved antioxidant capacities compared to plain chitosan treated in thesame conditions wit hou t gal lic aci d gra fti ng. Fur the rmore,theGA- g -chitosans alsoexhibited good cytocompatibility and effectively inhibited the formation of intracellular reactive oxygen species (ROS) in time- and dose-dependent manner in RAW264.7 macrophages. © 2010 Elsevier Ltd. All rights r eserved. 1. Intro ducti on The uncont rolled gener ation of react ive oxyge n specie s (ROS) and free radicals is involved in the pathogenesis of several human disea ses includ ing cancer , aging, and ather oscle rosis ( Moskovitz, Yim, & Chock, 2002). Ant ioxidantsreduceor ret ard fre e rad ical and ROS generation and prevent the oxidation of biomacromolecules including DNA, membrane lipids, and proteins. Several synthetic antio xida nts are exten sively used; howev er, these antioxida nts must be used under strict regulations due to their potential risk in vivo. Therefore, much attention has been given to the use of naturally occurring antioxidants to inhibit oxidative damage. Chitosan has been chemically and enzymatically modiﬁed to imp art new phy sical and chemical pro per tie s, and numerous resear ch worksregardin g antio xidan t activ ityhave beencarriedout (Guo et al., 2005; Muzzarelli & Muzzarelli, 2005; Sousa, Guebitz, & Kokol, 2009; Xing et al., 2005; Zhong, Zhong, Xing, Li, & Mo, 2010 ). Pol yph enols are usuall y ref erred to as a diverse group of natur ally occurr ing compo unds conta ining mult iple pheno lic funct ional ities (Tuchmantel , Kozi kowski , & Roma nczyk , 1999 ). Natu rally occurrin g poly pheno ls are known to have numerous biolo gical activitie s; in part icula r, they have recent ly receiv ed atten tion as antio xida nts. It has been suggested that ingest ing ∗ Correspond ing author. Tel.: +82 61 659 3416; fax: +82 61 659 3419. E-mail address: [email protected] (J.-Y. Je). polyphenols may be beneﬁcial to human health ( Flight & Clifton, 2006). Galli c aci d (GA) is a natura l phenol ic ant iox ida nt ext rac tab le from plants, especially green tea (Lu, Nie, Belton, Tang, & Zhao, 2006), and is widely used in foods, drugs, and cosmetics. It is possible to reduce the intra- and intermolecular hydrogen bond networks of chitosan by means of the bulky group of the benzene ring of GA, and to increase the antioxidant ability of chitosan by conjugation of GA onto chitosan. The obj ective of this stu dy was to synthesiz e GA- grafted- chitosans and to evaluate their antioxidant properties in different antio xidan t assay s, in orderto verifythe possi bilit y for appl icati ons in functional foods and/or the pharmaceutical industry. 2. Mater ials a nd metho ds 2.1. Materials The chitos an was kindly donat ed by Kit to Lif e Co. (Seoul, Korea). The average molecular weight and degree of deacetylation were 310 kDa and 90%, respecti vely. Gallic acid, 2,2- diph enyl-1 - picrylhydrazyl (DPPH), Folin-Ciocalteau’s phenol reagent, hydrogen peroxide, 2,2-azino-bis(3-et hylbenzthiazoline)-6-sul fonic acid (ABTS), peroxidase, and potassium ferricyanide were purchased from Sigma Chemical Co. (St. Louis, MO, USA). All other chemi- cals and reagents used in this study were of analytical grade and commercially available. 0144-8617/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2010.10.019

preparation, characterization, and antioxidant properties of gallic

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