Acetylation in Ionic Liquids Dramatically Increases Yield in the Glycosyl Composition and Linkage Analysis of Insoluble and Acidic Polysaccharides

Glycosyl composition and linkage analyses are importantfirst stepstoward understanding the structural diversity and biological importanceof polysaccharides. Failure to fully solubilize samples prior to analysisresults in the generation of incomplete and poor-quality compositionand linkage data by gas chromatography-mass spectrometry (GC-MS).Acidic polysaccharides also do not give accurate linkage results,because they are poorly soluble in DMSO and tend to undergo & beta;-eliminationduring permethylation. Ionic liquids can solubilize polysaccharides,improving their derivatization and extraction for analysis. We showthat water-insoluble polysaccharides become much more amenable tochemical analysis by first acetylating them in an ionic liquid. Onceacetylated, these polysaccharides, having been deprived of their intermolecularhydrogen bonds, are hydrolyzed more readily for glycosyl compositionanalysis or methylated more efficiently for glycosyl linkage analysis.Acetylation in an ionic liquid greatly improves composition analysisof insoluble polysaccharides when compared to analysis without acetylation,enabling complete composition determination of normally recalcitrantpolysaccharides. We also present a protocol for uronic acid linkageanalysis that incorporates this preacetylation step. This protocolproduces partially methylated alditol acetate derivatives in highyield with minimal & beta;-elimination and gives sensitive linkageresults for acidic polysaccharides that more accurately reflect thestructures being analyzed. We use important plant polysaccharidesto show that the preacetylation step leads to superior results comparedto traditional methodologies.

Automated summary

Glycosyl composition and linkage analyses are crucial steps in understanding the structure and biological importance of polysaccharides. Failure to fully solubilize samples before analysis can lead to incomplete and poor-quality data. Ionic liquids can improve the solubility of polysaccharides, facilitating their analysis. Preacetylation in an ionic liquid greatly enhances the composition and linkage analysis of insoluble polysaccharides, providing more accurate results compared to traditional methods.