Spatial Distribution and Characterization of the Small-Molecule Metabolites and <i>In Situ</i> Hydrolyzed Oligosaccharides in the Rhizome of <i>Glycyrrhiza uralensis</i> by Desorption Electrospray Ionization-Mass Spectrometry Imaging and High-Resolution Liquid Chromatography–Mass Spectrometry
Yuying Zhao, Meiting Jiang, Meiyu Liu, Hongda Wang, Wei Wang, Tingting Zhang, Xiaoxuan Tian, Lili Hong, Feifei Yang, Yu Wang, Yadan Zou, Heshui Yu, Zheng Li, Wenzhi Yang
Abstract
Characterization and spatial distribution studies of the metabolome in plants are crucial for revealing the physiology of plants and developing functional foods. Using the rhizome of Glycyrrhiza uralensis as a case, we integrated desorption electrospray ionization-mass spectrometry imaging (DESI-MSI) and high-resolution liquid chromatography/mass spectrometry approaches aimed at characterizing and locating both the small molecules and the macromolecular polysaccharides. Under the optimal conditions, 21 flavonoids and 12 triterpenoids were detected and characterized in different tissues of the rhizome and another 19 components were characterized exclusively by DESI-MSI. Combined with hydrophilic interaction chromatography/ion mobility-quadrupole time-of-flight mass spectrometry, eight different degrees of polymerization of oligosaccharides (after in situ acid hydrolysis) were characterized from the rhizome of G. uralensis . Majority of these metabolites are located in the cortex, phloem, and medulla, which lays the foundation for understanding the physiology of G. uralensis . The useful information can benefit the sustainable utilization and further development of Glycyrrhiza resource.