4,6-Diphenylpyrimidine Derivatives as Dual Inhibitors of Monoamine Oxidase and Acetylcholinesterase for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with multifactorial pathogenesis. Monoamine oxidase (MAO) and acetylcholinesterase enzymes (AChE) are potential targets for the treatment of AD. A total of 15 new propargyl containing 4,6-diphenylpyrimidine derivatives were synthesized and screened for the MAO and AChE inhibition activities along with ROS production inhibition and metal-chelation potential. All the synthesized compounds were found to be selective and potent inhibitors of MAO-A and AChE enzymes at nanomolar concentrations. VB1 was found to be the most potent MAO-A and BuChE inhibitor with IC₅₀ values of 18.34 ± 0.38 nM and 0.666 ± 0.03 μM, respectively. It also showed potent AChE inhibition with an IC₅₀ value of 30.46 ± 0.23 nM. Compound VB8 was found to be the most potent AChE inhibitor with an IC₅₀ value of 9.54 ± 0.07 nM and displayed an IC₅₀ value of 1010 ± 70.42 nM against the MAO-A isoform. In the cytotoxic studies, these compounds were found to be nontoxic to the human neuroblastoma SH-SY5Y cells even at 25 μM concentration. All the compounds were found to be reversible inhibitors of MAO-A and AChE enzymes. In addition, these compounds also showed good neuroprotective properties against 6-OHDA- and H₂O₂-induced neurotoxicity in SH-SY5Y cells. All the compounds accommodate nicely to the hydrophobic cavity of MAO-A and AChE enzymes. In the molecular dynamics simulation studies, both VB1 and VB8 were found to be stable in the respective cavities for 30 ns. Thus, 4,6-diphenylpyrimidine derivatives can act as promising leads in the development of dual-acting inhibitors targeting MAO-A and AChE enzymes for the treatment of Alzheimer's disease.