Reinvestigation of Aconitum flavum Hand-Mazz resulted in the isolation of five new diterpenoid alkaloids, i.e., dehydronapelline (1), 12-acetyllucidusuuline (2), 1-epi-napelline (3), 12-epi-napelline (4), and 1-demethylhypaconitine (9), along with napelline, lucidusculine, aconitine, 3-acetylaconitine, deoxyaconitine, flavaconitine, benzoylaconine, and neoline. The structures of these new compounds were determined based on spectral data and chemical transformations. The pharmacological tests showed that 12-acetyllucidusculine (2) has a strong effect of lowering of heart rate in Langendorff's guinea pig hearts. © 1987.