Low-polymerization compositional fingerprinting for characterization of Schisandra polysaccharides by hydrophilic interaction liquid chromatography-electrospray mass spectrometry

A hydrophilic interaction liquid chromatography-negative electrospray-mass spectrometry (HILIC-ESI−-MS) coupled with microwave assisted mild acid (MAMA) depolymerization is proposed here for unusual discrimination and characterization of plant polysaccharides: a case study of fruit polysaccharides in Schisandra chinensis and S. sphenanthera (SCP and SSP). The optimized MAMA hydrolysis procedure was proposed for sample preparations of low-polymerization saccharides (Mw < 5000 Da) released in SCP and SSP. In addition, HILIC-MS/MS was employed for elucidation of isomeric glycosidic linkages in terms of 18O labelling. The MAMA hydrolysates showed that the amount of neutral →(4Hex1)n→ moiety is confirmed to be more bigger than that of acidic →(4HexA1)n → in SCP, whereas the amount of acidic →(4HexA1)n→ moiety seems to be more bigger than that of neutral →(4Hex1)n→ in SSP. The resulting low-polymerization compositional fingerprinting (LCF) showed the performance on rapid visualization of SCP and SSP by HILIC-MIM-MS. Principal components analysis (PCA) and hierarchical cluster analysis (HCA) further unveils several key Q-markers (e.g., m/z 503, 369, 665, 827, 989, 1151 and 735) for rapid discrimination of SCP and SSP. This practical study showed that the LCF with PCA and HCA could effectively reflect structural differences and could rapidly achieve discrimination of SCP and SSP.