Modern Research Center for Traditional Chinese Medicine, School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing 100029, China.
Guizhou Hanfang Pharmaceutical Co. Ltd., Guiyang 550014, China.
J Pharm Biomed Anal. 2022 Mar 20;211:114634. doi: 10.1016/j.jpba.2022.114634. Epub 2022 Jan 31.
Proanthocyanidins (PACs) refer to a group of polyphenols consisting of flavan-3-ol units, and are ubiquitously distributed in fruits, vegetables, nuts and grains. PACs possess high-level structural diversity because of the fickle linkage manners amongst units, the polymerization degree and stereoisomeric forms, thus leading to a great challenge for structural analysis. Although LC-MS/MS currently serves as the workhorse to profile PACs in complicated matrices, it's still challenging to achieve confirmatively structural annotation even employing the cutting-edged high-resolution MS/MS techniques, and the key technical obstacle lies at isomeric discrimination. To pursue as many auxiliary structural clues as possible, full collision energy ramp-MS (FCER-MS) spectrum was conceptually designed here to involve all mass fragmentation behaviors of a given compound, such as m/z, optimal collision energy (OCE) and the maximal relative ion intensity (RII) aiming to advance the structural annotation confidences of PACs through reliably differentiating isomers. Thirteen authentic compounds were collected to mine relationships between chemical structures and FCER-MS spectra that were correlated by three progressive steps: (1) recording MS/MS spectrum by LC-Q-TOF-MS; (2) proposing mass fragmentation pathways to assign those obvious fragment ion species; and (3) acquiring breakdown graph for each concerned fragment ion species by programming online energy-resolved mass spectrometry to compose FCER-MS spectrum. Afterwards, the rules were applied for PACs-focused chemical characterization of a medicinal herb namely Indigofera stachyodes (Chinese name: Xuerenshen), and as a result, 22 PACs were captured and more importantly, isomerically identified by deciphering FCER-MS spectra. Therefore, FCER-MS spectrum provides a promising way to achieve in-depth isomeric discrimination of, but not limited to, PACs.
原花青素（PACs）是指一组由黄烷-3-醇单元组成的多酚类化合物，广泛分布于水果、蔬菜、坚果和谷物中。由于单元之间的连接方式、聚合度和立体异构形式的多变，PACs 具有高水平的结构多样性，这导致结构分析极具挑战性。尽管 LC-MS/MS 目前是分析复杂基质中 PACs 的主力，但即使采用最先进的高分辨率 MS/MS 技术，实现结构确证性注释仍然具有挑战性，关键技术障碍在于异构体的区分。为了尽可能多地获得辅助结构线索，本研究从概念上设计了全碰撞能量 ramp-MS（FCER-MS）谱，以涉及给定化合物的所有质量碎片化行为，例如 m/z、最佳碰撞能量（OCE）和最大相对离子强度（RII），旨在通过可靠地区分异构体来提高 PACs 结构注释的置信度。收集了 13 种纯化合物，通过三个渐进步骤挖掘化学结构与 FCER-MS 谱之间的关系：（1）通过 LC-Q-TOF-MS 记录 MS/MS 谱；（2）提出质量碎片化途径来分配那些明显的碎片离子种类；（3）通过编程在线能量分辨质谱为每个相关的碎片离子种类获取分解图，以组成 FCER-MS 谱。之后，将这些规则应用于药用植物菘蓝（中文名：血人参）的 PACs 化学特征分析，结果捕获到 22 种 PACs，并通过解析 FCER-MS 谱更重要的是，对其进行了异构体鉴定。因此，FCER-MS 谱为深入进行异构体区分提供了一种有前途的方法，但不仅限于 PACs。
