Untargeted metabolomics analysis to unveil the chemical markers for the differentiation among three Gleditsia sinensis-derived herbal medicines by ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry

Precise identification and differentiation among those congeneric Traditional Chinese Medicines (TCMs) or derived from the same plant trend to be more challenging, particularly in the absence of appearance characteristics. Three TCMs, involving Gleditsiae Sinensis Fructus (GSF), Gleditsiae Fructus Abnormalis (GFA), and Gleditsiae Spina (GS), recorded in Chinese Pharmacopoeia (2020 edition) are derived from Gleditsia sinensis, but prescribed for different clinical uses. The documents aimed to compare their chemical differences are rare, to date. An untargeted metabolomics approach, based on ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/QTOF-MS), was elaborated to unveil the potential chemical markers to differentiate among GSF, GFA, and GS. Good chromatographic separation of all the GSF/GFA/GS components was achieved within 33 min by utilizing a BEH C18 column, while data-independent MS^E in the positive mode was selected for profiling the metabolic features. Notably, the high-mass saponins (1300–2500 Da) gave unique protonated precursors ([M + H]⁺) in the positive ESI mode, compared with those complicated ion species occurring in the negative mode. Pattern recognition chemometrics analysis of 45 batches of G. sinensis samples could unveil 70 significantly altered ions assigned as 46 potentially differential components. The positive/negative high-accuracy MS² data analysis, phytochemical isolation/NMR analysis, and searching of an in-house library of G. sinensis, were utilized for structural elucidation. Three compounds (saikachinoside A, locustoside A, and locustoside B) rich in GSF could be the markers to differentiate from GFA/GS, while four components were characteristic for GS. These results obtained can greatly benefit the quality control of TCMs derived from G. sinensis.