C19-Diterpenoid alkaloids from Aconitum richardsonianum

Abstract

Three new aconitine-type C 19 -diterpenoid alkaloids, richardsonines A-C ( 1–3 ), were isolated from the roots of Aconitum richardsonianum Lauener, together with seventeen known compounds ( 4–20 ). Their structures were elucidated by extensive spectroscopic analysis, and the absolute stereochemistry of 1 was confirmed by X-ray crystallography. Compounds 2 , 5 , 8 and 9 were rare C 19 -diterpenoid alkaloids bearing an OH group at C-16. Isolated compounds were evaluated for inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated neuroinflammatory responses in BV-2 microglial cells. Compounds 3 and 7 showed weak antineuroinflammatory effects with inhibition rates of 35.32 ± 2.29% and 39.94 ± 2.50%, respectively, at a concentration of 100 µM. • Three new diterpenoid alkaloids were isolated from A. richardsonianum . • Richardsonine B is a rare C 19 -diterpenoid alkaloid bearing a C 16 -OH moiety. • The antineuroinflammatory effects of the isolated compounds were evaluated.