New antidepressant diterpenoid alkaloids from Aconitum carmichaelii Debeaux: Potential inhibitors of NLRP3 activation.

Targeting NOD-like receptor protein 3 (NLRP3) holds promise as a novel strategy for treating depression. Chemical investigation of the lateral roots of Aconitum carmichaelii Debeaux (Fuzi) led to the isolation of five new diterpenoid alkaloids acarmalines A-E (1-5). Their structures were elucidated based on the spectroscopic analysis (1D, 2D NMR, HR-ESI-MS, and IR) and quantum chemical calculations. Their biosynthetic pathways were also discussed. Bioactivity studies demonstrated that 1, 2, 4 and 5 showed significant neuroprotective effects in LPS-stimulated BV2 cells. Notably, compound 1 revealed remarkable antidepressant effects in the tail suspension test (TST) of mice at a dose of 0.1 mg/kg, with efficacy comparable to the positive control fluoxetine (10 mg/kg). Furthermore, mechanistic studies indicated that 1 exhibited significant anti-neuroinflammatory effects through modulation of the NLRP3 pathway by western blot and immunofluorescence experiments. Finally, cellular thermal shift assay (CETSA) and molecular docking studies confirmed that 1 might acted as an inhibitor of NLRP3 activation. These findings provide a rationale for designing NLRP3 activation inhibitors as novel antidepressant agents.