Study On Preparation Of Se-polysaccharides Based On Sulfonic Acid Functionalized Ionic Liquids

In recent years,Se-containing polysaccharides had been attracted extensive attention in research on structure-activity relationship,which were attributed to the combined high activity and low toxicity of Se and polysaccharides.However,the low selenium content of selenized polysaccharides were observed by microbial fermentation culture or conventional HNO₃-H₂SeO₃ method,and the molecular weight was difficult to control,which couldn't meet the further research on the structure-activity relationship of Se-polysaccharides derivatives.Therefore,exploring new reaction system played crucial role on improving selenylation activity.In recent years,ionic liquids had shown excellent properties in the field of biomass conversion and catalytic derivatization of polysaccharides.As an efficient catalyst,sulfonic acid functionalized ionic liquids?SFILS?provided a new idea for the polysaccharides selenylation.Artemisia sphaerocephala as rich in resources is an important sand-fixing plant in northwestern China.In the previous studies,A.sphaerocephala polysaccharide?PAS?was extracted from oil residue of seed by classical hot water extraction method,and a series of research on PAS active derivatives was carried out.Guar gum?GG?is an important food additive with many biological activities.PAS and GG were used as experimental materials.In order to improve the selenium content and realize the controllable regulation of weight average molecular weight?M_W?.SFILS with different anion and cation structures were used as catalysts to synthesize selenized polysaccharides in the new reaction system which composed of DMSO and SFILS.The effects and rules of different anion and cation structures on selenylation were studied by analyzing the changes of selenium contents and M_W.The main research contents and conclusions of this paper were as follows:1.Synthesis of Se-polysaccharides by using C3SO3HMIm ionic liquidsThe catalysts consisted of different anions?Cl^-,HSO₄^-,NO₃^-,BF₄^-,AcO and CH₃SO₃^-?and propylsulfonic imidazole-based cation.SePAS and SeGG were synthesized in reaction system which composed of DMSO and C₃SO₃HMIm catalysts.The selenium contents of SePAS and SeGG increased significantly compared with the traditional synthetic system,indicating C₃SO₃HMIm could efficiently enhanced selenylation reactivity,which due to the protonation effect of H₂SeO₃ by C₃SO₃HMIm.The acidities of C₃SO₃HMIm showed the positive and negative regulatory effect on selenium content and M_W,respectively.The stronger the acidity,the higher the selenium content and the lower the M_W gradually.2.Synthesis of Se-polysaccharides by using C4SO3HMIm and C6SO3HMImA series of C₆SO₃HMIm were synthesized by using sulfonic acid functionalized imidazole groups with different side chains?butyl and benzyl?as cations and Cl^-,HSO₄^-,AcO and CH₃SO₃^-as anions,and they were characterized.Se-polysaccharides were synthesized in the reaction system of C₄SO₃HMIm and C₆SO₃HMIm with DMSO.The both ionic liquids could effectively increase selenium content.The results showed that the selenium content of SePAS was lower than that of C₄SO₃HMIm.This was due to the limited ability to dissociate protons,which attributed to the strong conjugative effect of benzyl group.FT-IR,¹³C NMR,SEC-MALLS and AFM results exhibited that selenylation was successful and the substitution position was at C-6,and the molecular morphology of derivatives polysaccharide chains was related to the selenium content and M_W.The results showed that the structure of Se-polysaccharides could be regulated to a certain extent by changing the composition of anions and cations.In summary,the new reaction system composed of SFILS with different anions and cations and DMSO could effectively enhance the selenylation reactivity and increase the selenium content of Se-polysaccharides.The synergistic effect of anions and cations could regulate the selenium content and M_W of selenized polysaccharides.It showed certain reference value for rationally designing the structure of active polysaccharide derivatives and studying the structure-activity relationship of selenized polysaccharides in the later period.