Synthesis Of Chitosan Oligosaccharides And Their Metal Ion Complexes

Chitooligosaccharides are extracted from chitin from shells of shrimps and crabs,which are linked by P-1,4 glucosidic linkages from 2-10 glucosamine to low molecular weight chitosan.As the only positively charged,alkaline,water-soluble polysaccharide,chitooligosaccharide has not only the advantages of small molecular weight and high solubility,but also has many unique physiological activity and functional properties.Chitooligosaccharide molecules contain large amounts of hydroxyl and amino groups,it can rely on hydrogen bonding or salt bond to form a cage-like molecules with similar network structure,easy and metal ion coordination reaction to produce chitooligosaccharide metal complexes,and this Complexes have not only the excellent properties of chitooligosaccharides,but also have the related properties of metal ions,which are widely used in the fields of health food production and development,metal separation and content detection,biomedicine and so on.Therefore,chitooligosaccharide metal complexes have important research significance and practical application value.The effect of temperature,time and concentration of hydrogen peroxide on the degradation of chitooligosaccharides was studied.The optimum conditions for preparation of chitooligosaccharides were obtained by viscosity-average molecular weight determination.The reaction temperature was 60 ?,the reaction time was 6h and the mass fraction of hydrogen peroxide was 3%.Under these conditions,the viscosity average molecular weight of chitooligosaccharides was about 2.11 × 103.COS-Fe,COS-Cu and COS-Ni were used as the saccharide metal complexes.The product was characterized by UV and IR.The results showed that the product was the coordination product of metal elements of chitooligosaccharides.The optimum conditions for coordination of Fe3+,Cu2+ and Ni2+ were identified as coordination solution PH value should be controlled at about 4-5,the reaction time should be controlled at 60min,the reaction temperature was controlled at 40-50 ?;The coordination ratio of chitooligosaccharide to Fe(?).is 3:1,the ratio of chitooligosaccharide to Cu(II)is 2:1,the ratio of chitooligosaccharide to Ni(II)is 3:1.