Identification and visualization of component changes during the processing of ginseng to red ginseng using UPLC-Q-Orbitrap HRMS and MALDI-MSI techniques

Red ginseng, a processed product of ginseng, has been shown to possess various pharmacological effects. To investigate the changes in ginsenosides during the processing of ginseng into red ginseng and to visualize their spatial distribution characteristics in tissues, ultra-high performance liquid chromatography coupled with hybrid quadrupole-orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS) was used to detect and identify the extracts of ginseng and red ginseng. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to visually analyze the spatial distribution and temporal changes of prototype ginsenosides and their metabolites in ginseng. The UPLC-Q-Orbitrap HRMS results showed the identification of 42 major ginsenosides in both ginseng and red ginseng. Additionally, PCA and OPLS-DA analyses identified the processing-related markers for ginseng and red ginseng. During the processing of ginseng into red ginseng, the content of protopanaxadiol ginsenosides decreased (Rb1, Rc, Rd, etc.), while the types and content of rare ginsenosides increased (Rg3, Rg5, Rh1, etc.). The MALDI-MSI tissue distribution results demonstrated that ginsenosides in ginseng were mainly distributed in the cambium and phloem, while the processing led to the transformation of ginsenosides and an increase in distribution in the xylem and medulla. This study comprehensively reveals the chemical diversity and dynamic transformation patterns during the processing of ginseng, providing more substantial foundational information for research on red ginseng processing techniques. The transformation of these rare ginsenosides also indicates that ginseng is more beneficial for pharmacological applications such as anti-tumor, anti-allergic, and liver protection after being processed into red ginseng.