Identification of isoquinoline alkaloids from Corydalis mucronifera and their acetylcholinesterase inhibitory effects.

Four new spirobenzylisoquinoline mucroniferanines N - Q (1-4) and a rare chlorinated isoquinoline mucroniferanine R (5) were isolated from Corydalis mucronifera Maxim. Their structures were elucidated based on extensive spectroscopic data analysis of HRESIMS, 1D and 2D NMR, and their absolute configurations were confirmed by ECD data. The isolated compounds were evaluated for acetylcholinesterase (AChE) inhibitory activities. Mucroniferanine R showed significant activities with IC50 values of 0.78 µM compared to galanthamine (1.34 µM). The AChE inhibitory activity was further supported by the molecular docking analysis that exhibited the accommodation of mucroniferanine R in the active site of human AChE.