Analysis on structure and immunostimulatory activity of polysaccharides from Dunaliella salina by fractional precipitation
Polysaccharide of different molecular weights from Dunaliella salina(polysaccharide of Dunaliella salina,PD)was pre-pared by 40％,60％and 80％of ethanol fractional precipitation,which were named PD-40,PD-60 and PD-80,respectively.The physi-cochemical properties such as HPGPC,FT-IR,monosaccharide composition,SEM,TGA and Congo red assay of the three polysaccharide components were analyzed,and in vitro immune activity was also evaluated in RAW 264.7 cell culture.Results indicated that when the ethanol concentration increased to 40％,60％and 80％(v/v),three PD components with decreasing molecular weight(PD-40＞PD-60＞PD-80)were produced sequentially,and there was no difference in structure or thermal stability based on the FT-IR and TGA analysis.Meanwhile,three PD components were all composed of 10 monosaccharide residues with different molar ratios,among them,the PD40 component had the largest content and molecular weight(Mw=2.31 × 107),accounting for 61.4％of the total PD mass,and also had the highest galactose(Gal)molar ratio and uronic acid content.Additionally,PD40 components could significantly enhance the production of NO and ROS as well as the phagocytic activity in RAW 264.7 cells.Ethanol fractional precipitation is an effective method for isolating immunoactive PD from D.salina while reducing solvent consumption.
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