Discovery of methoxy-naphthyl linked N-(1-benzylpiperidine) benzamide as a blood-brain permeable dual inhibitor of acetylcholinesterase and butyrylcholinesterase

The cholinesterase enzymes play a vital role in maintaining balanced levels of the neurotransmitter acetylcholine in the central nervous system. However, the overexpression of these enzymes results in hampered neurotransmission. Both the major forms of cholinesterase enzymes viz. acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) play a crucial role in blocking neurotransmission; therefore, in recent years, a strategy of dual cholinesterase inhibition is being explored. Herein, we developed an energy-optimized e-pharmacophore hypothesis AHHPRR from AChE-donepezil complex and screened a set of 15 scaffolds that were designed imaginarily. The ligand with N-(1-benzylpyridinium) benzamide framework has shown the highest fitness and volume score, which was chosen for synthesis and validation. A series of pyridinium benzamides were synthesized and screened for cholinesterase inhibition that led to the identification of 7b, a naphthalene containing N-(1-benzylpiperidine) benzamide as a potent dual AChE and BChE inhibitor with IC50 values of 0.176, and 0.47 μM, respectively. The kinetic study indicated that 7b inhibits AChE in a non-competitive manner with Ki value of 0.21 μM, and BChE in a mixed-fashion with Ki of 0.15 μM. The observed mode of inhibition was corroborated with molecular docking studies. The MD simulation studies pointed out that both AChE and BChE undergo low conformational changes in complex with 7b. The benzamide 7b displayed high BBB permeability in PAMPA assay, which indicates its potential for further exploration in preclinical studies for Alzheimer's disease.