Integrated strategy of mass spectrometry imaging and LC/MS-based GNPS for spatial characterization of alkaloids from Menispermi Rhizoma and study on potential anti-inflammatory mechanism by network pharmacology and molecular docking

Menispermi Rhizoma (MR) is the dried rhizome of Menispermum dauricum DC, which has been used to treat sore throat, enteritis, and rheumatic arthralgia. These therapeutic effects are attributed to its alkaloid ingredient. However, the chemical composition, anti-inflammatory mechanisms and the spatiotemporal distribution of the bioactive ingredients in MR have seldom been investigated. This study aims to clarify the anti-inflammation mechanism, material basis, and their spatial distribution of MR. Here, a LC/MS-based Global Natural Products Social Molecular Networking (GNPS) strategy was used to rapidly exhibit alkaloid molecular clusters that improve annotation accuracy and discover more unknown compounds. Then, a high-sensitive air flow-assisted ionization mass spectrometry imaging (AFAI-MSI) method was developed to visualize the spatial distributions alkaloids in different botanical parts of MR. The anti-inflammation mechanism was investigated based on network pharmacology and verified by molecular docking experiment. Finally, a total of 106 alkaloids including 24 aporphines, 23 monobenzylisoquinolines, 20 morphinanes, 20 proberberines, 12 bisbenzylisoquinolines, and 7 amides were identified in MR as well as 24 alkaloids were visualized in the medullary ray, cortex and epidermis regions. Moreover, the targets with a higher degree in the PPI network were TNF, GAPDH, AKT1, ALB, STAT3. GO and KEGG analysis revealed that MR in anti-inflammatory mechanism mainly involved plasma membrane, ATP binding, cytoplasm, identical protein binding and ATP binding. The signaling pathways mainly included NOD-like receptor signaling pathway, PI3K-Akt signaling pathway, AGE-RAGE signaling pathway in diabetic complications. The molecular docking results indicated that stepharanine-2-O-glucoside, bianfugedine, bianfugecine, dehydrostephanine had excellent affinity with SRC, MMP9 AKT1, STAT3 and TNF. This study comprehensively characterized the alkaloid ingredients and spatial distribution of MR, and revealed potential mechanism of MR in inflammation, which provides a reference for development and application of MR and other Traditional Chinese medicines (TCMs).