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

## TL;DR

This study identifies obacunone in Rhizoma coptidis as a TGR5 agonist, offering insights into its role in metabolic regulation and potential therapeutic use.

## Contribution

The study introduces obacunone as a novel TGR5 agonist from Rhizoma coptidis, validated through multiple experimental techniques.

## Key findings

- Obacunone was identified as a TGR5 agonist with a KD of 101 μM and EC50 of 9.6 μM.
- Transcriptomic analysis showed HMOX1 as the most significantly upregulated gene in response to obacunone.

## Abstract

Rhizoma coptidis (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 (HMOX1) 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.