Evaluation Antioxidant and cytotoxic activities of novel chitooligosaccharides prepared from chitosan via enzymatic hydrolysis and ultrafiltration

Our work was designed to evaluate antioxidant (free radical scavenging and reducing power) and cytotoxicity activities of chitooligosaccharides with different molecular weights. The antioxidant activities in vitro were assessed by three separated methods, including DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS (2,2-azinobis (3-methyl-benzothiazoline-6-sulfonic) free radical-scavenging assay systems and ferric reducing power (FRAP). Results were compared with that of trolox which was used as a reference compound. There was correlation between antioxidant activity and molecular weight of chitooligosaccharides. In general, lower molecular weights showed better activity than higher one. Chitooligosaccharides with molecular weight lower than 1 KDa showed highest antioxidant activity in the all tested methods (86.97to 93.56 µgTE/mg). Chitooligosaccharides with molecular weight less than 1.0 KDa group was analyzed by high-performance liquid chromatograph (HPLC). It mainly contained N-acetylglucose amine (36.7 %), chitobiose (29.1 %) and chitotetrose (23.51 %). The chitooligosaccharides groups were also subjected to investigate cytotoxic activity on three different carcinoma cells lines (HEPG2, HCT and MCF7). Cytotoxicity was evaluated by sulfohodamine B (SRB) cell viability assay in vitro. Chitooligosaccharides with molecular weight 10 to 100 KDa showed IC50 1.564, 1.84 and 2.208 µg/ml against HEPG2, HCT and MCF7 cells, respectively. While Chitooligosaccharides with molecular weight 1.0 to 10 KDa showed IC50 12.948 and 11.952µg/ml against HEPG2 and MCF7 cells, respectively. They caused 75 to 80% inhibition of the tested cells. Thus, the chitooligosaccarides had valuable antioxidant and cytotoxicity, which related to their molecular weights. Chitooligosaccharides may be used as a functional food ingredient in pharmaceutical and food industries future.