Gut Microbiota and Metabolite Remodeling Underlies the Anxiolytic Effect of Anshen Bunao Oral Liquid

Background/Objectives: Anshen Bunao Oral Liquid (ABOL) is a traditional medicinal formula comprising Cornu Cervi Pantotrichum, Radix Polygoni Multiflori Preparata and other ingredients. It replenishes essence, nourishes qi and blood, and soothes the spirit. It is used in clinical practice to treat neurasthenia and insomnia (emotion-related symptoms), and its key component, glycyrrhizin, exhibits anxiolytic properties. This aligns with the holistic approach of traditional Chinese medicine (TCM) to regulating neuropsychiatric disorders. The aim of this study is to evaluate the anxiolytic efficacy of ABOL in rats with anxiety induced by chronic restraint stress (CRS), and to clarify its mechanism by focusing on modulation of the gut–brain axis (microbiota and metabolism). Methods: Sprague-Dawley rats underwent three hours of restraint per day for 28 days to induce anxiety. ABOL was administered intragastrically in three doses. Anxiety-like behaviours were assessed using OFT, EPM and SPT. Serum, tissue and faecal samples were analysed using ELISA, histopathology, immunohistochemistry, non-targeted metabolomics, 16S rRNA sequencing and RT-qPCR. Results: CRS induced anxiety-like behaviours, impaired weight gain and perturbed the balance of neurotransmitters (decreasing 5-HT, GABA, NE and DA, while increasing CORT), inducing inflammation/oxidative stress, hippocampal neuronal injury, intestinal barrier dysfunction and gut microbiota/metabolic dysregulation. ABOL effectively reversed these abnormalities by restoring the balance of neurotransmitters and the HPA axis, suppressing inflammation and oxidation, protecting neurons and the intestinal barrier, remodelling the gut microbiota (enriching Akkermansia and balancing Firmicutes/Bacteroidota) and regulating sphingolipid and glycerophospholipid pathways. The interaction between the gut microbiota and metabolites may contribute to this pharmacological effect. Conclusions: ABOL exerts anxiolytic effects by modulating the gut–brain axis at multiple targets, involving microbiota remodelling, regulation of lipid metabolism and improvement of pathology. This validates its ethnopharmacological value, linking traditional Chinese medicine to the development of modern anxiolytics.