Antioxidant activity of N-carboxymethyl chitosan oligosaccharides

Three N-carboxymethyl chitosan oligosaccharides (N-CMCOSs) with different degrees of substitution (NA: 0.28, NB: 0.41, and NC: 0.54, respectively) were prepared by the control of the amount of glyoxylic acid in the etherification process of chitosan oligosaccharide (COS). Their antioxidant activities were evaluated by the scavenging of 1,1-diphenyl-2-picrylhrazyl radical (DPPH) radical, superoxide anion and determination of reducing power. With the increasing of substituting degree, the scavenging activity of N-CMCOSs against DPPH radical decreased and reducing power increased. As for superoxide anion scavenging, the order is NB>NC>NA. The difference may be related to the different radical scavenging mechanisms and donating effect of substituting carboxymethyl group.