An aporphine alkaloid from Nelumbo nucifera as an acetylcholinesterase inhibitor and the primary investigation for structure–activity correlations

Abstract

N-methylasimilobine (1), a new-found strong acetylcholinesterase (AChE) inhibitor, along with two weakly active aporphine alkaloids, nuciferine (2) and nornuciferine (3) were separated from Nelumbo nucifera. N-methylasimilobine (1) inhibited 50% of AChE activity at the concentrations of 1.5 ± 0.2 µg mL−1 when the standard IC50 value of Physostigmine was 0.013 ± 0.002 µg mL−1. The mode of AChE inhibition by 1 was reversible and non-competitive. In addition, molecular modelling was performed to explore the binding mode of inhibitor 1 at the active site of AChE.