Integration of multicomponent characterization, untargeted metabolomics and mass spectrometry imaging to unveil the holistic chemical transformations and key markers associated with wine steaming of Ligustri Lucidi Fructus

Processing of traditional Chinese medicine (TCM) can enhance the efficacy and/or reduce the toxicity. Currently available approaches regarding TCM processing generally focus on a few markers, rendering a one-sided strategy that fail to unveil the involved global chemical transformation. We herein present a strategy, by integrating enhanced multicomponent characterization, untargeted metabolomics, and mass spectrometry imaging (MSI), to visualize the chemical transformation and identify the markers associated with the wine steaming of Ligustri Lucidi Fructus (LLF), as a case. An ultra-high-performance liquid chromatography/quadrupole-Orbitrap mass spectrometry-based polarity-switching (between the negative and positive modes), precursor ions list-including data-dependent acquisition approach was developed, which enabled the simultaneous targeted/untargeted characterization of 158 components from LLF via one injection analysis. Holistic, continuous, and time-dependent chemical variation trajectory, among different processing time (0-12 h) for LLF, was depicted by principle component analysis. Pattern recognition chemometrics could unveil 20 markers, among which the peak area ratios of eight components to oleuropein aglycone, used as an internal standard, were diagnostic to identify the processed (both the commercial and in-house prepared) from the raw LLF. Four markers (10-hydroxyoleoside dimethylester, 8-demethyl-7-ketoliganin, elenolic acid, and salidroside) showed an increasing trend, while another four (neonuezhenide/isomer, verbascoside/isomer, luteoline, and nuzhenal A) decreased in LLF after processing. MSI visualized the spatial distribution in the fruit and indicated consistent variation trends for four major markers deduced by the untargeted metabolomics approach. This integral strategy, in contrast to the conventional approaches, gives more convincing data supporting the processing mechanism investigations of TCM from a macroscopic perspective.