Separation,Purification And Primary Structural Analysis Of Selenium Polysaccharide From Se-enriched Sweet Potato

As the combination product of selenium and polysaccharide,selenium polysaccharide can effectively avoid toxicity caused by inorganic selenium and exert the double effect of selenium and polysaccharide.Analyzing the structure and component of selenium polysaccharide plays an important role in revealing its biological function,so the analysis and research of selenium polysaccharide in selenium-enriched sweet potato is beneficial for exploring the biological functions of selenium polysaccharide and studying the pathogenesis of related disease,and it is also of great significance for the development and utilization of selenium-enriched sweet potato.In this paper,the structure of selenium polysaccharide in selenium-enriched sweet potato was preliminarily investigated through separating and purifying,and the major parameters of the process are as follows.First,selenium-enriched sweet potato was used as raw material,from which selenium polysaccharide was extracted and whose selenium content and polysaccharide content is 2.87 μg/g and 27.41%,respectively.Next,protein removal rate and polysaccharide retention rate were used as indicators to optimize the deproteinization process,and three deproteinization methods,including Sevag method,papain enzymatic hydrolysis and enzymatic hydrolysis combined with Sevag method,were investigated and compared to get the optimized parameters.Results showed that the enzymatic hydrolysis combined with Sevag method showed the best protein removal rate of 89.71%,along with the polysaccharide retention rate of 85.88% and selenium content of 1.05 μg/g.The purification of selenium polysaccharide was conducted by column chromatography,from which four components of Se-Sp-P1,Se-Sp-P2,Se-Sp-P3 and Se-Sp-P4 were obtained and preliminary analyzed by UV spectrophotometer,Fourier transform infrared spectroscopy(FT-IR),high performance liquid chromatography(HPLC)and scanning electron microscopy(SEM),respectively.The main objects were to investigate the physicochemical property,monosaccharide composition,whether there is uronic acid or not and its type,the type of glycosidic bond,the type of sugar ring,the existing way of selenium and the surface morphology.Results have shown that:(1)Se-Sp-P1 is a pyran neutral selenium polysaccharide with polysaccharide content of 98.91% and mostly composed of Glu;Se-Sp-P2,Se-Sp-P3 and Se-Sp-P4 were all pyran acidic selenium polysaccharides with β-glycosidic bond mostly constituted by GalUA and with the polysaccharide content of 57.65%,67.50% and 63.36%,respectively.(2)Selenium polysaccharides after purification are still amorphous,but the surface shows some changes,and they exists mainly in the forms of strips,filaments,granules and other irregular forms.