The present study was designed to he investigate 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 (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. 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 models (86.97 to 93.56 µg TE/mg). Chitooligosaccharides with molecular weight less than 1.0 KDa group was analyzed by HPLC. It mainly contained N-acetyl glucose amine (36.7 %), chitobiose (29.1 %) and chitotetrose (23.51 %). The chitooligosaccharides groups were also subjected to investigate cytotoxic activity on three different cancer 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 group 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 11.952 µg /ml against HEPG2 and MCF7 cells, respectively. They caused 75 to 80 % inhibition of the tested cells.
Key words: chitooligosaccharides, antioxidant, DPPH, ABTS and FRAP, cytotoxic, HEP-G, HCT-116 and MCF7 cell line, SRB assay and HPLC.
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