Synthesis,Characterization And Applications Of Chitooligosaccharides Schiff Base Metal Complexes

Chitooligosaccharide is the second largest natural polymer in the world and has a lot of excellent biological activities.However,it also has the following shortcoming:?1?Because the molecular structure of chitooligosaccharide contains a large amount of free amino groups,it belongs to a charged sugar,which is easily browned due to the Maillard reaction and is difficult to store.?2?Although chitooligosaccharide has a certain antibacterial effect,it is easy to affect its bactericidal ability because of its high viscosity.Based on the above factors,chitooligosaccharide derivatives and its complexes are prepared by modified molecular design of chitooligosaccharide,which is expected to make up for the shortcomings of chitooligosaccharide and further optimize its biological activity and broaden its application fields.The main work of this paper focuses on the preparation and applications of chitooligosaccharide Schiff base derivatives and their complexes.The specific research contents are as follows:?1?The chitooligosaccharide metal complexes were synthesized by solid state reaction at room temperature and liquid phase synthesis method using CuCl₂,MnSO₄,Ce?NO₃?₄,and chitooligosaccharide as raw materials.The chitooligosaccharide complexes were characterized by elemental analyses,ICP,FTIR,XRD and SEM.The results show that the chitooligosaccharide metal complexes have better antioxidant activity than chitooligosaccharide,and the scavenging ability of·O₂^–is gradually increased with the increase of mass concentration.?2?The metal complexes of La?III?,Cu?II?with chitooligosaccharide Schiff base ligand were synthesized by the ultrasonic reflux heating and solid state reaction methods.The chitooligosaccharide Schiff base and its complexes were screened for their antibacterial.The antibacterial activity of chitooligosaccharide Schiff base and its complexes was evaluated by the Oxford cup method,and its antioxidant capacity was tested by the method of scavenging the·O₂^–radical and DPPH free radicals.The results show that the introduction of the Schiff base C=N group and the coordination between the chitooligosaccharide Schiff base and copper?II?further enhance the antibacterial ability,the chitooligosaccharide Schiff base lanthanides?III?has excellent antioxidant activity at the concentration of 0.5 mg·mL^–1.?3?The copper?II?complexes of the chitooligosaccharide iodo-substituted salicylaldehyde Schiff bases?I-SCOS?were synthesized and characterized by elemental analyses,¹HNMR,ICP,FTIR and SEM.The antimicrobial activities of I-SCOS and their copper?II?complexes were investigated against Enterobacter cloacae,Staphylococcus aureus,Staphylococcus epidermidis and Staphylococcus saprophyticus.The results indicate that the coordination interaction of the chitooligosaccharide iodo-substituted salicylaldehyde Schiff base ligands and copper ions further enhances the antimicrobial activities.The scavenging superoxide anion radical activity of the COS derivatives was estimated by using NBT/VB₂/methionine superoxide anion radical producing system.The antioxidant function of SCOS was superior to that of COS at lower concentration.When the mass concentration of the chitooligosaccharide iodo-substituted salicylaldehyde Schiff base copper complexes was more than 0.3 mg·mL^–1,their antioxidant activity was higher than that of the chitooligosaccharide iodo-substituted salicylaldehyde Schiff base.