Isolation, Structure Elucidation, Semi-Synthesis, and Structural Modification of C-Diterpenoid Alkaloids from and Their Neuroprotective Activities.

Five new aconitine-type C-diterpenoid alkaloids, apetalrines A-E (-), were isolated from . Their structures were determined by analysis of 1D and 2D NMR, IR, and HRESIMS data. Semisynthesis of apetalrine B () from its parent compound aconorine was achieved to confirm the structure proposed. Twenty derivatives of (-, , , , , , , , ) were synthesized via a unified approach relying on simple coupling reactions. The evaluation of neuroprotective effects of compounds (-, , , -, , , , , , , ) with low cytotoxicity revealed compound to exhibit good neuroprotective effects in HO-treated SH-SY5Y cells at a concentration of 50 μM. A series of studies using flow cytometry, staining, and Western blotting on indicated that its neuroprotective effects may arise from inhibiting cell apoptosis.