Discovery of Obacunone as a TGR5 Agonist from Rhizoma coptidis: Affinity Screening, Functional Verification and Transcriptional Analysis

<i>Rhizoma coptidis</i> (RC), known as Huang Lian, is widely used for treating diabetes in Traditional Chinese Medicine. G protein-coupled bile acid receptor 1 (TGR5) is a potential therapeutic target for glucose-lipid metabolic disorders due to its capacity to stimulate glucagon-like peptide-1 (GLP-1) secretion. However, whether RC contains ingredients targeting TGR5 remains unclear. In this study, we screened 330 secondary metabolites of RC via molecular docking and identified obacunone as a top candidate. We confirmed binding using Cell Membrane Chromatography (CMC) and quantified affinity via Surface Plasmon Resonance (SPR), determining a KD of 101 μM. cAMP assays identified obacunone as an activator of TGR5. Subsequently, concentration-dependent cAMP assays characterized it as a partial agonist with an EC50 of 9.6 μM. Finally, transcriptomic profiling revealed a stress adaptation response, identifying Heme Oxygenase 1 (<i>HMOX1</i>) as the most significantly upregulated gene (padj = 9.99 × 10^-72, log₂FoldChange = 1.65). These findings contribute to understanding the pharmacological profile of RC and provide a screening example for identifying components with GPCR activity in RC.