A rare arcutine-type C20-diterpenoid alkaloid, named aconicarmicharcutinium A and obtained as hydroxide (1) and trifluoroacetate (1a), was characterized as a minor constituent of “fu zi” (the lateral roots of Aconitum carmichaelii). The structures of 1 and 1a were elucidated by comprehensive analysis of spectroscopic data including 19F and 2D NMR experiments. Compounds 1 and 1a represent the first examples of the arcutine-type C20-diterpenoid alkaloid iminium. © 2016 Jian-Gong Shi