Diterpenoid alkaloids from the lateral root of Aconitum carmichaelii

Abstract

Twenty-six new diterpenoid alkaloids, 1-26 (1-4: hetisan-type C 20-diterpenoid alkaloids; 5-26: aconitane C19-diterpenoid alkaloids), and two known analogues, hypaconitine 27 and benzoylmesaconine 28, have been isolated from a water extract of the lateral root of Aconitum carmichaelii. Compounds 7 and 8 are rare examples of conformational isomers obtained from the same material. The conformation and conformational transformation of ring A in the C19- diterpenoid alkaloids are discussed on the basis of NMR data analysis in combination with single-crystal X-ray crystallography of 6 and 27 by anomalous scattering of Cu K7α radiation. In preliminary analgesic and toxicity assays, the isomer with ring A in the chair conformation (8 or 27) was found to be more active than that with ring A in the boat conformation (7 or 27a). In addition, 15, 16, and 19 showed neuroprotective activity. © 2012 American Chemical Society and American Society of Pharmacognosy.