Chitosan-oligosaccharide Preparation By Nitrous Acid Method From Chitosan And Its Application

In this paper, A new controlled depolymerization to chitosan-oligosaccharide from chitosan by nitrous acid is presented. The reaction conditions are studied in detail, including reaction time, reaction apparatus, amount of sodium nitrous, reaction medium and chitosan materials specifications The average molecular weight of the chitosan-oligosaccharide is determined by terminal group method, viscosity method and HPLC. The structure of the chitosan-oligosaccharide is charactered by IR spectroscopy.'H NMR and 13C NMR.The broad spectrum of antimicrobial activity and MICs of different molecular weight chitosans are examined. It shows that the antimicrobial activity for Penicillium, bacterium and Streptomyces jinyangensis strengthens with increasing the concentrations of the chitosan-oligosaccharide. For St.aureus , E.coli and Bacillus subtilis, the antimicrobial activity of the chitosan-oligosaccharides strengthens with increasing the molecular weight. For E.coli and St.aureus, the MIC range is from 80ppm to 1250ppm and for Bacillus subtilis, the MIC is in the range of 10ppm to 157ppm. But For Penicillium chrysogenum, the antimicrobial activity of the chitosan-oligosaccharides gets weaker with the increasing the molecular weight. For Penicillium chrysogenum, the MIC range is from 2.5 ppm to 2500ppm. For Streptomyces jinyangensis, there isn't apparent relation between the antimicrobial activity and molecular weight. Chitosan-oligosaccharide of number-average molecular 3340 has the lowest MIC of SOppm; The highest MIC of the chitosan-oligosaccharides of viscosity-average, molecular 15,000 is 2500ppm. The antimicrobial activity of the chitosan-oligosaccharides gets stronger, with the higher D.D.The antioxidant activity of the prepared chitosan-oligosaccharides is studied. The scavenging ability of the chitosan-oligosaccharides on OH and O2- is determinedby l,10-phenanthroline-Fe2+ method and pyrogallic acid method,respectively. It is showed that the chitosan-oligosacchanride of number-average molecular 1070 has strongest scavenging effect on OH with the ICso at 27.5mmol/L in contrast of Glucosamine hydrochloride and Mannitol. The reduced power of the chitosan-oligosaccharides is determined by potassium ferricyanide method. It is showedthe reduced power of the chitosan-oligsaccharide A of number-average molecular weight 1070 is better than the chitosan-oligsaccharide B of number-average molecular 1780 and Glucosamine hydrochloride. It is investigated the scavenging ability of A with ICso 1.67mg/mL is better than B and Glucosamine hydrochloride. It shows that the reduced power has mutual correlation with antioxidative activity.Antitumor activity of the chitosan-oligosaccharides LI (Mn=1780) and L2 (Mn=1070) in mice with sarcoma-180 is evaluated. The result supports that LI and L2 obviously inhibit sarcoma-180 cell proliferation of mice with inhibition rate of 26.72% and 42.24% at the concentration of 50 mg.kg-1.d-1. The indexes of thymus, spleen, and liver have no vice-effect. But controlled CY lightens the indexes of thymus, spleen and liver remarkable. SOD values of injected mice with LI and L2 are higher than that of CY. It supports that the chitosan-oligsaccharides improve the immunity function in mice. But MDA valuer are higher than that of CY. It may give some damage to mice'cells. The antitumor activity of L2 is better than Li's.The elicitor effect of the chitosan-oligosaccharide is investigated by germination of seeds of soybean, mungbean, cowpea, red beans including the germination percentage, the germination index, the activity index and the peroxidase activity and so on. The changes of germination and some physiological indexes of mungbean seeds also are studied with 0.2%, 0.6%, 1.0% and 1.4% concentrations of chitosan solutions. It is suggested that the chitosan-oligosaccharide at the 1.0% concentration obviously enhances some physiological indexc .