Simultaneous determination of the monosaccharide types and their absolute configurations in polysaccharides based on UPLC-MS/MS

Analysing monosaccharide composition is an essential step in deciphering polysaccharide structures. However, it presents significant challenges due to the pronounced hydrophilicity and the vast array of monosaccharide isomers. Gas/liquid chromatography, coupled with an aldononitrile acetate derivatisation, has been widely used for monosaccharide composition analysis. However, it poses considerable difficulties in simultaneously determining the D/L configurations of these monosaccharides. In this study, a novel method that can simultaneously determine the composition of polysaccharides and their D/L configuration based on L-cysteine methyl ester derivatisation (CMED) and ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) is developed for the comprehensive analysis of monosaccharide types. This method enables the simultaneous characterization of aldoses, ketoses, alditols, and uronic acids. Furthermore, the reaction mechanisms and by-products were meticulously analysed, offering a robust theoretical basis for this novel methodology. Additionally, the developed method was employed to characterize the monosaccharide composition for six plant polysaccharides. Ultimately, the findings demonstrated that the proposed method is effective for confirming monosaccharide composition, encompassing both structural types and absolute configurations.