Study On The Application Of Deep Eutectic Solvent In The Synthesis Of Selenized Polysaccharides

Due to the strong inter-molecular and intra-molecular hydrogen bonds,many polysaccharides were extremely difficult to be dissolved in the fields of derivatization.The emergence of Deep eutectic solvent（DES）provided a broad platform for the synthesis of selenized polysaccharides.It could be achieved purpose for dissolving polysaccharides and promoting the selenium efficiency by destroying old hydrogen bonds in the polysaccharides and forming new hydrogen bond between the molecules.At the same time,DES could overcome the shortcomings of poor environmental friendliness for traditional solvents.Artemisia sphaerocephala as rich in resources was 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.Locust bean gum（LBG）,as one of galactomannans,was an important food and medicine additive with many biological activities.In this paper,a new reaction system composed of DES with different hydrogen bond donors（HBD）and different hydrogen bond receptors（HBA）,which was used to synthesize selenized polysaccharide with DMSO,based on PAS and LBG as raw materials.The regulation of different DES on selenized polysaccharides were studied by analyzing the changes of selenium contents and M_W.The main research contents and conclusions of this paper were as follows:3.Synthesis of Se-PAS/Se-LBG based on alcohol and amine DESThe DES with different polarity consisted of different HBA（ChCl and TMAC）and HBD（Urea,EG,Gly and BDO）.The regularity of polarity was obtained such as:DES₂>DES₃>DES₁>DES₄;DES₆>DES₇>DES₅>DES₈,and the polarity of DES_1-4formed by ChCl as HBA was generally higher than TMAC(DES_5-8).Se-PAS₂（4004.29μg/g）and Se-LBG₁₀（4926.54μg/g）were synthesized in reaction system which composed of DMSO/DES.The selenium contents of selenized polysaccharides increased significantly,which showed a dependence on DES polarity.1.Synthesis of selenized polysaccharide based on multi acidities of DESIn order to overcome the shortcomings of the traditional selenide reagents,acid sites were introduced into DES.A series of DES with different polarity and acidity were synthesized by using ChCl as HBA and 9 kinds of polybasic acids as HBD（Glyc、Ace、Hyd、Pro、Mal、Glut、Adi、Oxo、Cit）.The regularity of polarity and acidity were obtained such as:DES₁₆>DES₁₃>DES₁₂>DES₁₇>DES₁₄>DES₁₅>DES₁₀>DES₉>DES₁₁ and DES₁₃>DES₁₂>DES₁₇>DES₁₀>DES₁₁>DES₉>DES₁₄>DES₁₆>DES₁₅,respectively.Se-LBG was synthesized by co-solvent system composed of DMSO and DES.The increase of selenium contents of Se-LBG showed that acid functionalized DES could effectively increase selenium contents based on stronger polarity,which selenium content values were increased from 609.89μg/g to 11038.71¹4605.66μg/g corresponding DES based on Oxo,Mal and Pro.In addition,the results indicated that molecular weight（M_W）of Se-LBG were related to the H₀ values of DES.FT-IR,¹³C NMR,SEC-MALLS and molecular probe analysis exhibited that selenylation was successful and the substitution position was at C-6 of polysaccharide,and the anion functional groups were contributed to the rigid transformation of polysaccharide chains.In this paper,the structure of selenized polysaccharide was affected by the alkyl chain length,functional groups,polarity and acidity of HBD in the DES/DMSO cosolvent systems.The results indicated that the structure of selenized polysaccharide was affected by the alkyl chain length,functional groups,polarity and acidity of HBD in the DES/DMSO cosolvent systems.When the number of HBD functional groups was the same,the shorter the alkyl chain,the stronger the polarity and acidity;when the length of alkyl chain was the same,the polarity and acidity increased with the increase of the number of functional groups.The increasing Se contents of selenized polysaccharides indicated that DES could effectively enhance the selenylation reactivity,which had a certain reference value for the rational design of polysaccharide derivatives and the study of structure-activity relationship of selenized polysaccharides in the later stage.