Alkaloids from Erythrina crista-galli flowers and their inhibitory activities against acetylcholinesterase: in vitro and in silico studies

Abstract Acetylcholinesterase (AChE) is a hydrolytic enzyme that breaks down acetylcholine into choline and acetate. In patients with Alzheimer’s disease, the increased AChE activity may contribute to early degeneration of cholinergic neurons in the basal forebrain, resulting in impaired cholinergic signalling. This study aims to evaluate the anticholinesterase activity of alkaloids isolated from Erythrina crista-galli flowers through an integrated approach combining in vitro and in silico studies. Four alkaloids, namely cristamidine (1), erythrinine (2), erythraline (3), and 8-oxoerythrinine (4), were isolated and their structures were confirmed through high-resolution mass spectrometry (HR-MS) and nuclear magnetic resonance (NMR). In vitro assay conducted at a concentration of 50 µg/mL showed that cristamidine has the highest inhibition effect, followed by 8-oxoerythrinine, erythrinine, and erythraline. In silico studies comprising molecular docking and molecular dynamics simulations showed that both cristamidine and 8-oxoerythrinine formed stable interactions with the active pocket of AChE. This study highlights the potential of E. crista-galli as a natural source of AChE Inhibitors.