Novel triazole-based coumarin compounds as acetylcholinesterase inhibitors: Evidence and mechanism of 3-acetyl coumarin tethered (2-bromophenyl)-1,2,3 triazole as a potential mixed type inhibitor

Acetylcholinesterase (AChE) inhibition remains an important therapeutic strategy for Alzheimer's diseases, prompting immense research for novel and efficient small-molecule inhibitors. In this context, the present study describes the synthesis, characterization and evaluation of novel ether-linked 3-acetyl triazole-substituted coumarin derivatives as potential AChE inhibitors. The synthetic route involved 3-acetyl-7-hydroxycoumarin preparation through the reaction of 2,4-dihydoxybenzaldehyde with ethyl acetoacetate. Following alkylation at hydroxyl group, the acetylated 7-hydroxycoumarin underwent 1,3-dipolar cycloaddition i.e., Huisgen cycloaddition with various aromatic azides under sharpless click chemistry conditions, leading to the formation of a library of 16 novel coumarin tethered 1,2,3-triazole derivatives. Following synthesis and characterization using ¹H NMR, ¹³C NMR and IR spectroscopy, the AChE inhibitory potential of the coumarin derivatives was assessed, yielding IC₅₀ value in the range of 2.18 μM–67.89 μM. Among them, compound 9 exhibited the most potent inhibition (IC₅₀ = 2.18 μM), although lower than that of the standard inhibitor, eserine. Kinetic analysis indicated that compound 9 acted as a mixed-type inhibitor, with a K_i of 8.13 ± 0.18 μM. In silico simulation analysis elucidated the critical interactions between compound 9 and key AChE residues, including hydrogen bonding with Tyr121 and His444 and π-π stacking with Tyr334 and Trp283, supporting its strong binding affinity for the enzyme. Furthermore, the binding free energy calculations also confirmed the favourable thermodynamic interactions between the compound 9 and AChE. Collectively, the present findings highlight the therapeutic potential of compound 9 and establish this novel coumarin-triazole scaffold as a promising lead candidate for further optimization in development of AChE-targeted Alzheimer's therapeutics.