Antidepressant effects of supercritical CO2 extract of Citri Reticulatae Pericarpium through mediating gut microbiota dysbiosis, tryptophan and bile acid metabolisms

Citri Reticulatae Pericarpium (CRP) is a traditional Chinese medicinal herb with both medicinal and edible properties. The supercritical CO 2 extract of Citri Reticulatae Pericarpium (C-CRP) has shown potential antidepressant effects, but the precise mechanisms remain unclear. In this paper, we confirmed that C-CRP alleviated depressive-like behaviors in a chronic unpredictable mild stress (CUMS) depression rat model, as evidenced by increased sucrose preference in the sucrose preference test (SPT), increased total distance traveled in the open field test (OFT), reduced immobility time in both the tail suspension test (TST) and forced swim test (FST), and elevated serum levels of 5-hydroxytryptamine (5-HT), dopamine (DA), and norepinephrine (NE) in CUMS rats. C-CRP reshaped gut microbiota dysbiosis, significantly regulating the abundance of specific bacteria, including Lactobacillus , unclassified_f_Lachnospiraceae , Blautia , Allobaculum , Prevotella , and UCG-005 via 16S rRNA sequencing. Untargeted/targeted metabolomics indicated that C-CRP normalized the dysregulated metabolic profiles in plasma, urine, and feces of depressed rats, and identified tryptophan metabolism and bile acid metabolism as key routes through which C-CRP exerts its effects, which was corroborated by pathway-specific protein and metabolite changes. Through multivariate correlation analysis, Blautia was identified as a crucial gut bacterium associated with the antidepressant efficacy of C-CRP, which was further confirmed in lipopolysaccharide (LPS)-induced depression-like mice by oral administration of Blautia obeum . Thus, the findings demonstrate that C-CRP exerts antidepressant effects by modulating specific gut bacteria—most notably Blautia obeum —and regulating tryptophan and bile acid metabolic pathways, thereby alleviating depression-like behaviors in the CUMS rats.