Identification of Markers of Saccharides in Polygonati Rhizoma During the Steaming Process by MALDI-TOF Mass Spectrometry Imaging

Polygonati rhizoma is often used in Chinese medicine and as food. In this study, atmospheric pressure matrix-assisted laser desorption ionization and ion trap time-of-flight mass spectrometry techniques were applied to Polygonati rhizoma samples from Polygonati cyrtonema species. Positive ions were mainly detected in the mass range of m/z 200-600, while negative ions were mainly observed in the mass range of m/z 100-450. A total of 263 components were identified and the spatial distribution and changes in saccharides contents during the steaming process of Polygonati rhizoma were investigated. Monosaccharide and disaccharide exhibit a relatively uniform distribution, while the oligosaccharides were mainly found in the bast of fresh Polygonati rhizoma. Although the contents of monosaccharide and disaccharide were increased during steaming, that of trisaccharide, tetrasaccharide,and pentasaccharide were decreased. We used the five saccharide types with the greatest variation in content as variables for the principal component analysis (PCA) and cluster analysis. Both PCA and cluster analysis showed that these five saccharides can be used as markers in the steaming process of the Polygonati rhizoma. Present study of mass spectrometry imaging provides novel insights into the spatiotemporal accumulation patterns of saccharides in Polygonati rhizoma, improving our understanding of the steaming process.