Desulfation Methods Comparison Studies Of Marine Sulfated Polysaccharides

In this paper,κ-carrageenan was selected as starting material, the advantages and disadvantages in the desulfation of sulfated polysaccharide by PMA(Pyromellitic acid) Method, CTMS (trimethyl chlorosilane) Method, and DMSO-Methanol Method. The results showed that,κ-carrageenan was succesfully desulfated by three methods, the product yields were 62 %, 50.6 % and 36.7 %; the sulfate content of the product were 4.6%, 14.4% and 14.1%; the molecular weight of products were 4.75 kDa, 22.3 kDa and 15.7 kDa, separalely. FTIR data show that the desulfation product of PMA method has the lowest absorption at 1250 cm-1, which stand for the absorption of S=O vibration. Compared with three methods, PMA has the best desulfurization efficiency, highest product yield, and lowest degradation rate, all these feature made PMA Method to be the ideal desulfation method.In order to test the efficiency of PMA Method,λ-carrageenan, who have higher sulfate content(every two sugar residues containing three sulfate groups), was selected to do the desulfation assay. IR analysis showed that the desulfurization was very effective. The desulfated polysaccharide was further degraded with mild acid, the mixture was separated and purified with gel chromatography and ion exchange chromatography. The desulfated oligosaccharides was prepared by Superdex peptide column. The oligosaccharide structures were analyzed with electrospray ionization mass spectrometry (ESIMS), and confirmed that dsλ2-dsλ6 were di- to hexa- galactosaccharide with similar backbone structure ofλ-carrageenan. Applying glycochip technology, the defulfated oligosaccharides dsλ2-dsλ6 showed higher affinity to RCA120, but the bingding ability was reduced compared with intactedλ-carr-oligosaccharides, this provided a methodology basis for obtaining desulfated polysaccharide/oligosaccharides , used in structure-activity relationship study. Different sources of marine sulfated polysaccharide, such asτ-carrageenan, Sargassum Pallidum polysaccharide and Schizochytrium limacinum polysaccharide, are used in the desulfation experiments by PMA Method,. According to the FTIR data, all kinks of sulfated polysaccharides were successfully desulfated with high efficiency. In the desulfurization ofτ-carrageenan, we also find that when some content of urea was properly add to PMA, can selectively get rid of C2-sulfate and reserve the C4-sulfate ofτ-carrageenan.Based on the systematical study, we proved that, PMA is the best method used in removing the sulfate of polysaccharide. Not only can remove all kinds of sulfate groups located in polysaccharides, but also can selective remove specific sulfate group when adding proper modifier. The work has an important contribution in structural analysis of polysaccharide, and more useful in methylation and linkages analysis of polysaccharides. The method offer the basis to prepare different polysaccharide with different sulfate content, which are very important in structure-activity relationship study and marine carbohydrate drug development.