Mass spectrometry-based profiling and imaging strategy, a fit-for-purpose tool for unveiling the transformations of ginsenosides in Panax notoginseng during processing

Background: Panax notoginseng, a valuable medicinal plant, is traditionally used to treat trauma, body pain, and cardiovascular diseases in two clinical forms including raw (crude) and processed form. Processing-triggered compound transformation is responsible for the distinct bioactivity between raw and processed Panax notoginseng. Nevertheless, investigating the chemical diversity and dynamic transformation pattern of processed Panax notoginseng is challenging.Methods: A new approach, which integrates multi-components characterization, processing trajectory depiction, discovery of differential markers, transformation mechanism of metabolites, in situ spatial distribution and transformation of metabolites, was established to elucidate the role of processing on the holistic chemical transformations of Panax notoginseng (PN).Results: In this study, 136 ginsenosides (mainly rare ginsenosides) were identified or tentatively characterized and the temperature-dependent chemical variation trajectory was depicted via principal component analysis (PCA). Nineteen processing-associated markers were confirmed by orthogonal partial least squares-discriminant analysis (OPLS-DA). For the first time, the transformation pathway of ginsenosides during processing were elucidated by integrating the precursor ion scan (PIS) and mimic processing strategy that involves with deglycosylation, dehydration, hydration, acetylation, and isomerization. Results of mass spectrometry imaging (MSI) revealed the major ginsenosides M-Rb1, R1, Rg1, Rb1, Rd, and Re exhibited distinct spatial distribution pattern that are highly abundant in the xylem and showed a downward trend during processing. We firstly depicted the spatial distribution of processing-triggered rare ginsenosides (Rg3, Rk1, Rg5, etc.), and in situ transformation of ginsenosides was discovered in the process of steaming. Additionally, this variation trend was consistent with untargeted metabolomics results.Conclusion: This study comprehensively revealed chemical diversity and dynamic transformation pattern and depicted the spatial distribution of ginsenosides of PN during processing. It could provide a clue for the distinct bioactivities between raw and processed PN and elucidate the role of processing on the holistic chemical transformations of natural products, more importantly, the proposed strategy is valuable for the quality evaluation and control of the processing of natural product.