Anticholinesterase Activity of Budmunchiamine Alkaloids Revealed by Comparative Chemical Profiling of Two Albizia spp., Molecular Docking and Dynamic Studies.

Alzheimer's disease remains a global health challenge and an unmet need requiring innovative approaches to discover new drugs. The current study aimed to investigate the inhibitory activity of Albizia lucidior and Albizia procera leaves against acetylcholinesterase enzyme in vitro and explore their chemical compositions. Metabolic profiling of the bioactive plant, A. lucidior , via UHPLC/MS/MS-based Molecular Networking highlighted the richness of its ethanolic extract with budmunchiamine alkaloids, fourteen budmunchiamine alkaloids as well as four new putative ones were tentatively identified for the first time in A. lucidior . Pursuing these alkaloids in the fractions of A. lucidior extract via molecular networking revealed that alkaloids were mainly concentrated in the ethyl acetate fraction. In agreement, the alkaloid-rich fraction showed the most promising anticholinesterase activity (IC 50 5.26 µg/mL) versus the ethanolic extract and ethyl acetate fraction of A. lucidior (IC 50 24.89 and 6.90 µg/mL, respectively), compared to donepezil (IC 50 3.90 µg/mL). Furthermore, deep in silico studies of tentatively identified alkaloids of A. lucidior were performed. Notably, normethyl budmunchiamine K revealed superior stability and receptor binding affinity compared to the two used references: donepezil and the co-crystallized inhibitor (MF2 700). This was concluded based on molecular docking, molecular dynamics simulations and molecular mechanics generalized born/solvent accessibility (MM-GBSA) calculations.