Synthesis,Crystal Structure And Antioxidant Activities Of Water Soluble Salicylaldehyde Complexes With Chiral Schiff Base Ligand

The superoxide anion(O2·-)is a by-product of the mitochondrial respiratory chain and plays a role in a number of medical issues,including inflammation,ischemia-reperfusion injuries and carcinogenesis.Superoxide dismutases(SODs)catalyse the disproportionation of O2·-to hydrogen peroxide(H2O2)and dioxygen(O2)to protect cells from oxidative damage caused by O2·-.However,there are some drawbacks,such as high cost,poor permeability,short cycle and so on.Consequently its application are restricted,the search for SOD mimics has attracted great attention.Salicylaldehyde and its derivatives react with some amine to form Schiff base(Salen),which possess favourable ability of carrying oxygen and simulation biological enzyme for catalytic experiments,has attracted the attention of scientists at home and abroad.Surprisingly,the tested salen complexes are only slightly soluble in water,as a result its activity was affected.Hence,we have synthesized some metal complexes with better solubility in aqueous as superoxide dismutase mimics(SODm).Namely,5-sulfosalicylaldehyde sodium potassium salt and 1,2-diaminopropane,ethylenediamine were respectively used to synthesize the Schiff ligands with better solubility in aqueous to get transition metal complexes.The structure of these compounds have been determined by X-ray crystallographic methods and characterized by ESI Mass,FT-IR,element analyses.Moreover,the microenvironment of the protein could enhance the SOD activity of metal complexes,so our adopts metal complexes that we have synthesized with BSA to get hybrid proteins to simulate the activity of SOD.The SOD-like activities were tested by xanthine/xanthine oxidase method.Using ABTS method determined the oxidation resistance of the complexes and hybrid proteins.We also investigated the binding of complexes to BSA by multi-technique spectroscopy.This is benefical for antioxidant and catalytic activity design.In this paper,5-sulfosalicylaldehyde sodium potassium salt and 1,2-diaminopropane were used to synthesize the Schiff ligands(R-NaKH2L1 and S-NaKH2L1)with chiral and better solubility in aqueous to get six transition metal complexes by hydrothermal reaction,namely(Mn-la);(Mn-1b);(Co-2a);(Co-2b);(V-3a);(V-3b).Meanwhile,5-sulfosalicylaldehyde sodium potassium salt and ethylenediamine were used to synthesize the Schiff ligands(NaKH2L2)with better solubility in aqueous to get one transition metal complex by hydrothermal reaction,namely(Mn-4).The structures of part of them were determined by X-ray diffraction analysis.The SOD activity test results of complexes and hybrid proteins showed that apart from complexes V-3a and V-3b and its hybrid proteins had no SOD activity and other complexes and their corresponding hybrid proteins showed a certain SOD activity.The values of IC50 and Kcat have been obtained.The SOD activity of hybrid proteins is higher than that of the corresponding complex.The activity of the complex and hrybrid protein is in keeping with the metal ion of natural SOD.Manganese complex shows higher SOD activity than other metal complexes.In addition,SOD activity of these compounds influence by configuration,the S configuration has relatively higher activity than the R.The ABTS·+ radical scavenging capacity showed that the ability of hybrid proteins is more obvious than the complexes.The scavenging ability of Vanadium complexes show exceptional performance than other metal complexes.Based on the study of the activity of hybrid proteins in this paper,in the molecular level,we provide some basic theoretical information for the study of antioxidant capacity by the interaction of BSA with complexes.In the simulation of human physiological environment,fluorescence spectroscopy have been confirmed the interaction mechanism(fluorescence quenching mechanism,binding constants and number of binding sites).UV-vis spectroscopy and Synchronous fluorescence and circular dichroism have been used to study the effect of the ligands and their metal complexes on secondary structure of BSA.Raman spectra have been used to study the effect of the ligands and their metal complexes on the amino acid residues microenvironment of BSA.Studies have shown that the ligands and these complexes on the fluorescence quenching of BSA was mainly a static quenching process;at the same time they had a certain degree of influence on the secondary structure,tyrosine and tryptophan,disulfide bond of BSA.