Diterpenoid Alkaloids from the Roots of Aconitum sinomontanum and Their Evaluation of Immunotoxicity

 One new C18-diterpenoid alkaloid, along with four known diterpenoid alkaloids have been isolated from the roots of Aconitum sinomontanum.  Their structures were established as sinomontanine I (1), delcosine (2), lepenine (3), napelline (4), and kirinine B (5) by extensive spectroscopic techniques and chemical methods.The immunosuppressive effects of compounds 1–4 were evaluated in vitro through ConA-induced or LPS-induced splenocyte proliferation, with IC50 values of 8.909 μM, 1.515 μM，5.078 μM, and 1.167 μM (ConA-induced)，or 3.661 μM, 4.417 μM, 5.129 μM, and 1.830 μM (LPS-induced), and compounds 1–4 showed a significant cytotoxic effect with CC50 values of 447.5 μM, 702.2 μM, 310.6 μM and 794.1 μM, respectively. The CC50/IC50 value of 2 and 3 suggested that these compounds were potential immunosuppressive agents for the treatment of autoimmune diseases characterized by arthritis, such as rheumatoid arthritis..