Structure-based inhibition of acetylcholinesterase and butyrylcholinesterase with 2-Aryl-6-carboxamide benzoxazole derivatives: synthesis, enzymatic assay, and in silico studies

Abstract

An important research topic is the discovery of multifunctional compounds targeting different disease-causing components. This research aimed to design and synthesize a series of 2-aryl-6-carboxamide benzoxazole derivatives that inhibit cholinesterases on both the peripheral anionic and catalytic anionic sides. Compounds (7-48) were prepared from 4-amino-3-hydroxybenzoic acid in three steps. The Ellman test, molecular docking with Maestro, and molecular dynamics simulation studies with Desmond were done (Schrodinger, 12.8.117). Compound 36, the most potent compound among the 42 new compounds synthesized, had an inhibitory concentration of IC₅₀ 12.62 nM for AChE and IC₅₀ 25.45 nM for BChE (whereas donepezil was 69.3 nM and 63.0 nM, respectively). Additionally, compound 36 had docking values ​​of - 7.29 kcal/mol for AChE and - 6.71 kcal/mol for BChE (whereas donepezil was - 6.49 kcal/mol and - 5.057 kcal/mol, respectively). Furthermore, molecular dynamics simulations revealed that compound 36 is stable in the active gorges of both AChE (average RMSD: 1.98 Å) and BChE (average RMSD: 2.2 Å) (donepezil had average RMSD: 1.65 Å and 2.7 Å, respectively). The results show that compound 36 is a potent, selective, mixed-type dual inhibitor of both acetylcholinesterase and butyrylcholinesterase. It does this by binding to both the catalytically active and peripheral anionic sites of cholinesterases at the same time. These findings show that target compounds may be useful for establishing the structural basis for new anti-Alzheimer agents.

Keywords: Acetylcholinesterase; Benzoxazole; Butyrylcholinesterase; Enzyme inhibition; Molecular docking and dynamic simulation.

Fig. 1

Some FDA-approved anti-Alzheimer drugs

Fig. 2

Some benzoxazole derivatives for AChE inhibition

Fig. 3

Our designed fragment-based compounds for AChE and BChE inhibition

Scheme 1

General synthesis method. Reagents and conditions: (i) 1–2 drops H₂SO₄, MeOH, reflux (ii) Firstly; EtOH, rt, 6–24 h, Secondly; Catalytic NaCN, DMF, rt, 1 h. (iii) AlCl₃, DCM, rt, 24 h

Fig. 4

The Lineweaver-Burk graphs of novel 2-aryl-6-carboxamide benzoxazole derivatives (compound 36) against AChE and BChE.

Fig. 5

Superimposition of the top docking poses of the compounds 7–48 in AChE (A). Similar binding modes of donepezil (red) and compound 36 (green) in AChE (B)

Fig. 6

3D mode of interactions of compound 36 (A) and donepezil (B) with receptor AChE. C atoms are presented in green; N atoms are presented in blue and O atoms are presented in red respectively; π-cation interactions are shown in dark green; π-π interactions are shown in light blue

Fig. 7

RMSD plot of 100ns molecular dynamic simulations for compound 36 inside AChE. Blue: Cα (RMSD evolution of the protein). Pink: Lig fit Prot (RMSD of the ligand when the protein-ligand complex)

Fig. 8

Superimposition of the top docking poses of the compounds 7–48 in BChE (A). Similar binding modes of compound 36 (green) and donepezil (red) in BChE (B)

Fig. 9

3D mode of interactions of compound 36 (A) and donepezil (B) with receptor BChE. C atoms are presented in green; N atoms are presented in blue and O atoms are presented in red respectively; hydrogen bonds are shown in yellow, π-cation interactions are shown in dark green; π-π interactions are shown in light blue

Fig. 10

RMSD plot of 100ns molecular dynamic simulations for 36 inside BChE. Blue: Cα (RMSD evolution of the protein). Pink: Lig fit Prot (RMSD of the ligand when the protein-ligand complex)