Application of MALDI-mass spectrometry imaging in spatial distribution of secondary metabolites in medicinal plants -- a case study of Lepdium meyenii root / 中国中药杂志

Matrix-assisted laser desorption/ionization mass spectrometry imaging(MALDI-MSI) is a novel technique for in-situ distribution of various substances in tissue without labeling. This technique is increasingly applied to the study of medicinal plants owing to its high spatial resolution and its potential of in-situ analysis in small molecules. In this study, the structural information and their fragmentation patterns of the midazole alkaloids(1,3-dibenzyl-4,5-dimethylimidazolium chloride and 1,3-dibenzyl-2,4,5-trimethylimi-dazolium chloride) and benzylglucosinolate in the medicinal plant Maca(Lepdium meyeni) root were analyzed by ultra-high-performance liquid phase combined with LTQ-Orbitrap mass spectrometry(UHPLC-HR-MS). The localization of these active ingredients in the cross-sections of Maca root was performed by MALDI-MSI. These results demonstrated that the two types of imidazole alkaloids had a similar distributed pattern. They were located more in the cortex and the periderm than those in the medulla of a lateral root, while the localization of benzylglucosinolate was concentrated in the center of the root rather than in the cortex and the periderm. The precise spatial distribution of various secondary metabolites in tissue provides an important scientific basis for the accumulation of medicinal plant active ingredients in tissues. In addition, this imaging method is a promising technique for the rapid evaluation and identification of the active ingredients of traditional Chinese medicine in plant tissues, as well as assisting the research on the processing of medicinal plants.

Mass spectrometry imaging technology and its application in medicinal plants research / 中国中药杂志

As an important molecular imaging technology, mass spectrometry imaging(MSI) converts the ionic strength, mass-charge ratio and coordinates of ionized molecules in specific areas recorded by mass spectrometer into a pixel model by special imaging analysis software, and reconstructs the spatial ion distribution image of the compounds tested. It has the advantages of simple sample preparation, high sensitivity and no need for labeling. In recent years, MSI technology has been widely used in medicine, pharmacy, botany and other fields. Among them, the application of MSI technology in the research of medicinal plants provides a new technical idea for clarifying the pharmacological mechanism, improving the curative effect, tracking the distribution of toxic components, and makes an important contribution to the further development and utilization of medicinal plants. This review summarizes the research results of MSI technology in recent years for identification of medicinal plants, distribution of metabolites, pathway of active ingredient synthesis, medicinal safety and plant defense, and discusses the advantages and disadvantages of different research methods. Finally, the advantages and practical obstacles of MSI technology in medicinal plant research are briefly pointed out, and the prospects for the future development of MSI technology and medicinal plant research are also prospected.

Application of DESI-MSI in Quality Control of Banxia Xiexintang / 中国实验方剂学杂志

Objective::To prepare 15 batches of Banxia Xiexintang substance benchmark and lyophilized powder from different places, and the lyophilized powder was analyzed by ultra-high performance liquid chromatography with diode array detection (UHPLC-DAD) and desorption electrospray ionization-mass spectrometry imaging (DESI-MSI) in order to investigate the advantages of DESI-MSI in quality control of famous classical formulas. Method::Taking Banxia Xiexintang as the research model, fingerprints of the substance benchmark and lyophilized powder were established by UHPLC-DAD, and the content of index components and the yield of dry extract were also investigated. Meanwhile, as the research carrier, the lyophilized powder corresponding to Banxia Xiexintang was dissolved in methanol and dotted on qualitative filter paper with 5 μL quantitative capillary, and fixed it on the slide to make samples. The samples were analyzed on a DESI-MSI system in positive and negative ion mode with methanol-formic acid (1 000∶1, flow rate of 3 μL·min-1) as spray solvent, N2 as spray gas (pressure of 0.5 MPa). The scanning range was 100-1 200 Da, the spatial resolution was 300 μm, the spray voltage was 3 kV, the sampling cone voltage was ±40 V, incidence angle of sprayer was 60 degree, its collection angle was 10 degree, the ion source temperature was 120 ℃. Result::DESI-MSI could not only detect the index components of liquiritin, baicalin and wogonoside, as well as the common peaks of liquiritin apioside, berberine and glycyrrhizic acid, but also analyzed them semi-quantitatively, the analysis results were basically consistent with UHPLC-DAD. At the same time, DESI-MSI could detect 16 other components from Glycyrrhizae Radix et Rhizoma, Coptidis Rhizoma, Scutellariae Radix, Jujubae Fructus and Ginseng Radix et Rhizoma, such as licoricesaponin G2, palmatine, coptisine, rutin and ginsenoside Rg1, and present their relative content visually. The qualitative analysis ability of DESI-MSI was much better than UHPLC-DAD. Conclusion::DESI-MSI can be used as the quality control method for substance benchmark and lyophilized powder and dispensing granules of famous classical formulas with advantages of high sensitivity, strong analytical ability, no complex sample processing, qualitative and relative content analysis of complex samples without reference substance.