Extraction,separation and structural characterization of polysaccharides from Neverita didyma

Objective To extract and purify polysaccharides from Neverita didyma,and investigate their chemical properties and structural features.Methods Neverita didyma polysaccharides were extracted by distilled water and alkali solution sequentially,and purified by DEAE Sepharose FF anion-exchange and Sepharcryl S-300 gel-permeation chromatography.The contents of total sugar,protein,uronic acid,sulfate and amino sugar were determined by various chemical methods,and monosaccharide compositions were analyzed by high performance liquid chromatography.The structure of polysaccharides was characterized by methylation analysis,GC/MS,FT-IR,ESI-MS and NMR techniques.Results No uronic acid,sulfate and amino sugar were found in the water-extracted polysaccharide(BYL-S) and its monosaccharide composition was simple,which only included Glc.Four water-soluble fractions were isolated by further purification from BYL-S.While BYL-J had complex monosaccharide composition,including Glc,Man,GlcN,GalN,Gal and Fuc,and their molar ratio was Glc∶ Man∶ GlcN∶GalN∶Gal: Fuc=78.9∶1.7∶3.4∶2.2∶5.2∶5.6.After further isolation,three fractions were obtained from BYL-J.The structure of BYL-S2 was characterized to be composed of α-(1→4)-D-glucopyranose,with little β-(1→3,4) and β-(1→3) branched units.Conclusion Seven polysaccharides were separated from Neverita didyma and the structure of a water-soluble polysaccharide(BYL-S2) was determined.These results will provide basis for further research on relationships of structure and activity of Neverita didyma polysaccharides.