Preparation, characterization, and antioxidant activity of water-soluble oligochitosan

The preparation of oligochitosan through the heterogeneous degradation of chitosan/H 2 O 2 combined with the homogeneous reaction of chitosan with H 2 O 2 under gamma radiation was studied. Oligochitosan with weight-average molecular weight (M w ) of less than 10 kDa could be efficiently prepared by gamma Co 60 irradiation of chitosan solution (4%) and hydrogen peroxide (0.5%) at doses ranging from 8 to 24 kGy. The M w , chemical structure, and the crystallinity of chitosan and oligochitosan were characterized by GPC, FT-IR, and XRD. The solubility and antioxidant activity of chitosan and of oligochitosan with the different molecular weights were investigated. Results showed that oligochitosan CS 5 (20 kGy) and CS 6 (24 kGy) have good solubility in the pH range of 3 to –11. The scavenge percentage of CS 5 against 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical is 99.2% in 90 min. The antioxidant activity of oligochitosan is effective in a short time period; therefore, it has potential application as an effective and natural antioxidant.