•Three new lycodine-type Lycopodium alkaloids were isolated from Lycopodiastrum casuarinoides.•Lycocasuarine A (1) possesses a rearranged five-membered ring D resulting from C-8/C-15 cleavage and a new C-7/C-15 linkage.•Lycocasuarine B (2) is the first Lycopodium alkaloid found to bear an additional carbon (C-17) directly bonded to C-8.•Lycocasuarine C (3) showed inhibitory activity against acetylcholinesterase.Three lycodine-type Lycopodium alkaloids (1–3) were isolated from Lycopodiastrum casuarinoides. Their structures were elucidated by spectroscopic analysis, single-crystal X-ray crystallography, and computational methods. Compound 1 possesses a rearranged five-membered ring D resulting from C-8/C-15 cleavage and a new C-7/C-15 linkage. Compound 2 is the first Lycopodium alkaloid found to bear an additional carbon (C-17) directly bonded to C-8, which is particularly unusual from a biogenetic point of view. Compounds 1–3 were evaluated for acetylcholinesterase inhibitory activities.Download high-res image (79KB)Download full-size image