Department of Life and Nanopharmaceutical Sciences, College of Pharmacy, Kyung Hee University, Hoegi-dong 1, Dongdaemun-gu, Seoul 02447, Korea.
Division of Pharmacognosy, College of Pharmacy, Kyung Hee University, Hoegi-dong 1, Dongdaemun-gu, Seoul 02447, Korea.
Molecules. 2021 Jan 22;26(3):580. doi: 10.3390/molecules26030580.
Mass spectrometry-based molecular imaging has been utilized to map the spatial distribution of target metabolites in various matrixes. Among the diverse mass spectrometry techniques, matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) is the most popular for molecular imaging due to its powerful spatial resolution. This unparalleled high resolution, however, can paradoxically act as a bottleneck when the bio-imaging of large areas, such as a whole plant, is required. To address this issue and provide a more versatile tool for large scale bio-imaging, direct analysis in real-time-time of flight-mass spectrometry (DART-TOF-MS), an ambient ionization MS, was applied to whole plant bio-imaging of a medicinal plant, Ephedrae Herba. The whole aerial part of the plant was cut into 10-20 cm long pieces, and each part was further cut longitudinally to compare the contents of major ephedra alkaloids between the outer surface and inner part of the stem. Using optimized DART-TOF-MS conditions, molecular imaging of major ephedra alkaloids of the whole aerial part of a single plant was successfully achieved. The concentration of alkaloids analyzed in this study was found to be higher on the inner section than the outer surface of stems. Moreover, side branches, which are used in traditional medicine, represented a far higher concentration of alkaloids than the main stem. In terms of the spatial metabolic distribution, the contents of alkaloids gradually decreased towards the end of branch tips. In this study, a fast and simple macro-scale MS imaging of the whole plant was successfully developed using DART-TOF-MS. This application on the localization of secondary metabolites in whole plants can provide an area of new research using ambient ionization mass spectroscopy and an unprecedented macro-scale view of the biosynthesis and distribution of active components in medicinal plants.
基于质谱的分子成像已被用于绘制各种基质中靶代谢物的空间分布。在各种质谱技术中，基质辅助激光解吸/电离质谱（MALDI-MS）由于其强大的空间分辨率，是分子成像中最常用的技术。然而，这种无与伦比的高分辨率在需要对大面积生物进行成像（如整株植物）时，反而会成为一个瓶颈。为了解决这个问题，并为大规模生物成像提供更通用的工具，我们将直接实时飞行时间质谱（DART-TOF-MS），一种大气离子化质谱，应用于药用植物麻黄草的全植物生物成像。将植株的全部地上部分切成 10-20cm 长的段，然后进一步将每个部分纵向切开，以比较茎的内外表面主要麻黄生物碱的含量。使用优化的 DART-TOF-MS 条件，成功实现了单株植物全地上部分主要麻黄生物碱的分子成像。本研究分析的生物碱浓度在内茎段高于外表面。此外，在传统医学中使用的侧枝的生物碱含量远高于主茎。在空间代谢分布方面，生物碱的含量逐渐向侧枝末端减少。在这项研究中，我们成功地使用 DART-TOF-MS 快速简便地对整株植物进行了宏观尺度的 MS 成像。这项在全植物中定位次生代谢物的应用，可以为使用大气离子化质谱进行新的研究提供一个领域，并为药用植物中活性成分的生物合成和分布提供一个前所未有的宏观视角。
