<scp><i>Rhus chinensis</i></scp> Mill Derived Anti‐Allergic Ingredients Screening Using MAS‐Related G Protein‐Coupled Receptor X2 Cell Membrane Chromatography

Mas-related G-protein coupled receptor member X2 (MrgprX2) serves as a potential therapeutic target for pseudoallergic reactions. Cell membrane chromatography (CMC) is an efficient and reliable technique for screening active components from complex systems, which can be used to search for MrgprX2 antagonists in herbs. Therefore, we used a previously constructed MrgprX2-HALO-tag/CMC-HPLC-MS system specifically for identifying natural antagonists. Rhus chinensis Mill has been found to possess anti-inflammatory activities, but its active components targeting MrgprX2 remain unexplored. In this study, the MrgprX2-HALO-tag/CMC-HPLC-MS method successfully identified fisetin as the first reported MrgprX2-targeting component from Rhus chinensis Mill. Through frontal analysis, we demonstrated that fisetin exhibits strong binding affinity (K_D = 2.02 μM) with MrgprX2, representing the first quantitative assessment of this interaction. Molecular docking revealed four key binding residues (TRP248, ASP184, LEU247, and GLU164) that form stable interactions with fisetin. Pharmacological validation using LAD2 cells confirmed fisetin's potent anti-allergic activity via MrgprX2 antagonism. In summary, these findings not only identify fisetin as an active constituent of Rhus chinensis Mill but also further confirm that it targeted MrgprX2 to exert anti-inflammatory properties, offering new perspectives for developing anti-pseudoallergic therapeutics.