Visualization Analysis of Spatial Distribution of Notoginsenoside by Matrix-assisted Laser Desorption Ionization Mass Spectrometry Imaging

Mass spectrometry signals were obtained from the mixtures of five matrixes and three standard product combinations. The five matrixes were 2,5-dihydroxybenzoic acid (DHB), alpha-cyan-4-hydroxycinnamic acid (CHCA) , graphene (GR), graphene oxide ( GO ) and carbon nanotubes (CNT) , while the three standard products were ginsenoside Rg(1) ginsenoside Rb-1 and notoginsenoside R-1 DHB was utilized as a suitable matrix. After vacuum drying the 20 mu m thick frozen sections of Panax notoginseng rhizome 14 40 min , DHB was evenly coated on the section surface over 60 cycles, with a spray strength of 30%, a spray time of 1 s, an incubation time of 40 s and a drying time of 60 s. The data acquisition quality range was m/z 0-1500. PEG-600 was used for mass/charge ratio calibration and matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) was performed in 1000 Hz positive ion reflection mode. The spatial distribution of ten saponins in the cork layer, phloem, xylem and pith of Panax notoginseng rhizome was obtained. The t-distributed stochastic neighbor embedding ( t-SNE ) algorithm was used to analyze the data. A distinction between 2-year and 3-year panax notoginseng rhizomes was realized. This study provided an in-situ and visual method for the characterization of metabolites in the rhizome of Panax notoginseng and also provided valuable information for obtaining information on the specificity of Panax notoginseng.