Abstract
Background: Chaihu–Huangqin (CHHQ, Bupleuri Radix–Scutellariae Radix) is the core drug pair of Xiaochaihu Decoction, yet the constituents that reach the brain and the pathways they engage remain largely unknown.
Methods: An integrated strategy combining serum pharmacochemistry, brain-region-resolved distribution profiling, network pharmacology, molecular docking, and in vivo validation was developed in a chronic unpredictable mild stress (CUMS) rat model.
Results: UPLC-MS/MS-based serum pharmacochemistry identified 97 constituents absorbed into the systemic circulation. In CUMS rats, CHHQ ameliorated depressive-like behaviors, evidenced by increased sucrose preference and reduced immobility in the forced swimming test, without evident hepatic or renal toxicity. Profiling across six depression-related brain regions revealed the largest number of region-specific candidates in the dorsal raphe nucleus (DRN), which was therefore selected as the focus region. Network pharmacology prioritized inflammatory and serotonergic signaling, including the nuclear factor-κB (NF-κB)/NOD-like receptor family pyrin domain-containing 3 (NLRP3)/Caspase-1 axis and the serotonin transporter (SERT), and molecular docking gave GlideScore values of −6.01 to −10.50. In the DRN, CHHQ attenuated microglial activation, decreased TNF-α, IL-1β, and IL-18, and downregulated NF-κB, NLRP3, and Caspase-1, accompanied by restored SERT expression.
Conclusion: These findings establish an “absorption into blood—brain-region-resolved detection—DRN candidate prioritization” workflow and provide new insights into the material basis and multi-target mechanism of the CHHQ drug pair.