Monosaccharide Analysis of Dendrobium moniliforme Polysaccharides by High Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry

To obtain monosaccharide components information of Dendrobium moniliforme polysaccharides, a HPLC-ESI-MS method was proposed. The crude polysaccharides were extracted and purified from D. moniliforme as samples (DMP). Then, the polysaccharides were hydrolyzed with trifluoroacetic acid (TFA) and derivated by 1-phenyl-3-methyl-5-pyrazolone (PMP). PMP-labeled mixture of monosaccharides were separated by a reverse-phase high performance liquid chromatography (HPLC) and detected by on-line electrospray ionization mass spectrometry (ESI-MS). With this method, the six monosaccharide derivatives have been well separated and the identification of the monosaccharides composition was carried out. The result showed that D. moniliforme polysaccharide consisted of D-mannose, D-ribose, D-glucose, D-galactose and L-arabinose, in a molar ratio of 51.83: 4.01: 38.90: 4.20: 1.65, respectively. Moreover, hydrolysis studies revealed that the monosaccharide concentrations reached the peak value at different time and it suggested that the release of DMP monosaccharides was not hydrolyzed at the same rate. These results indicated that the DMP may be a mixture of multiple polysaccharides. Finally, we used a high performance gel permeation chromatography (HPGPC) method proved that crude polysaccharides were composed by three kinds of polysaccharides (DMP-1, DMP-2 and DMP-3) with molecular weight of 153.1 kDa, 69.28 kDa and 50.14 kDa.