Abstract: Three N-succinyl chitosan oligosaccharides (NSCOSs) with different substituting degrees (NSCOSA:0.25,NSCOSB:0.57 and NSCOSC:0.70,respectively) were prepared by reacting of chitosan oligosaccharide (COS) and succinic anhydride.The structure changes of the COS derivatives were characterized by Fourier transform infrared (FT-IR) spectra.Their antioxidant activities were evaluated by the scavenging of superoxide radical O₂^·,hydroxyl radical ·OH, 1,1-diphenyl-2-picrylhrazyl radical (DPPH) and determination of reducing power.The results indicated that all the NSCOSs showed obvious antioxidant activity,the orders of their scavenging effect on O₂^· was NSCOSB>NSCOSA>NSCOSC,the scavenging effect on ·OH decreased with the increasing of substituting degrees (DSs), the orders of their scavenging effect on DPPH and reducing power both were:NSCOSA>NSCOSC>NSCOSB.The result may be related with the substituting degrees,the properties of the substituting group and the different scavenging mechanisms against free radicals.

Key words: chitosan oligosaccharide, N-succinyl chitosan oligosaccharide, antioxidant activity