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

The preparation of oligochitosan through the heterogeneous degradation of chitosan/H2O2 combined with the homogeneous reaction of chitosan with H2O2 under gamma radiation was studied. Oligochitosan with weight-average molecular weight (Mw) of less than 10 kDa could be efficiently prepared by gamma Co60 irradiation of chitosan solution (4%) and hydrogen peroxide (0.5%) at doses ranging from 8 to 24 kGy. The Mw, 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 CS5 (20 kGy) and CS6 (24 kGy) have good solubility in the pH range of 3 to –11. The scavenge percentage of CS5 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