Matrix-assisted laser desorption/ionization mass spectrometry imaging reveals "Spatial-Temporal-Content" changes of parishins in Gastrodiae Rhizoma during the steaming process.

Gastrodiae Rhizoma is a commonly used plant material for both medicine and food in China for thousands of years. Steaming as the main pre-processing method of Gastrodiae Rhizoma is the key to its quality formation. In this study, we established a high-coverage matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) method to visualize the spatial distribution of phenols in Gastrodiae Rhizoma. By optimizing 1,5-diaminonaphthalene as MALDI matrix in negative mode, the "spatial-temporal-content" changes of 13 phenols including 11 parishins in Gastrodiae Rhizoma during the steaming process were imaged. We also characterized the activity of two hydrolases related to parishins degradation during the steaming. Moreover, the degradation pathways of parishins in Gastrodiae Rhizoma were summarized. The integration of spatially-resolved parishins and corresponding hydrolases information revealed the scientific connotation of steaming as the processing method of Gastrodiae Rhizoma is to inactivate hydrolases and protect parishins, which provided theoretical support for the quality improvement and the standardized processing of Gastrodiae Rhizoma.