Stephapierrines A–H, new tetrahydroprotoberberine and aporphine alkaloids from the tubers of Stephania pierrei Diels and their anti-cholinesterase activities

Eight new alkaloids, which are four new tetrahydroprotoberberine alkaloids, stephapierrines A–D (1–4), and four new aporphine alkaloids, stephapierrines E–H (5–8), together with three new naturally occurring alkaloids (9–11) and thirty-four known alkaloids (12–45) were isolated from the tubers of Stephania pierrei Diels. The structures of the new compounds were elucidated by spectroscopic analysis and physical properties. The structures of the known compounds were characterized by comparison of their spectroscopic data with those previously reported. Compound 42 exhibited the strongest acetylcholinesterase (AChE) inhibitory activity, which was more active than galanthamine, the reference drug. Compound 23 showed the highest butyrylcholinesterase (BuChE) inhibitory activity, which was also more active than galanthamine. Molecular docking studies are in good agreement with the experimental results.