Two-step hydrolysis method for monosaccharide composition analysis of natural polysaccharides rich in uronic acids

Monosaccharide composition analysis is important to characterize the structure of complex carbohydrates. However, techniques for analyzing this in acidic polysaccharides are immature, due to incomplete hydrolysis. The aim of this paper is to provide an improved method for this using two-step acid hydrolysis combined with high-performance anion exchange chromatography. A weak acid was used to hydrolyze polysaccharides before hydrolyzing them with a strong acid to dissociate more monosaccharides. In the first step, samples were hydrolyzed using 0.09 M trifluoroacetic acid at 79 degrees C for 1.5 h to cleave some glycosidic bonds. After TFA removal, hydrolysis was continued at 100 degrees C for 2 h with 2 M sulfuric acid. The validity of this method was verified for acidic polysaccharides (including standard and three acidic polysaccharides from natural plants), and the total monosaccharides of all samples detected by the two-step acid hydrolysis method was significantly increased comparing to sulfuric acid hydrolysis alone. It suggests that this hydrolysis method could be applied to the monosaccharide composition analysis for acidic polysaccharides.