Dihydropyrimidines Emerge as Promising Dual-Acting Inhibitors Targeting Acetylcholinesterase and Monoamine Oxidases for Alzheimer's and Other Neurological Disorders

The pathogenesis of Alzheimer's disease (AD) is multifaceted, and more than one factor is deemed responsible for its genesis and progression. Hence, the multi-target approach seems plausible en route to the development of therapeutics targeting Alzheimer's in particular, and other neurological disorders, in general. Among the major factors responsible for AD are acetylcholinesterase and monoamine oxidase enzymes. Acetylcholine is an important neurotransmitter that plays a role in processing memory and learning. Deficiency of this neurotransmitter is observed in patients of AD; this is largely attributed to increased expression of the enzyme acetylcholinesterase (AChE) that is responsible for breakdown of acetylcholine neurotransmitter. Hence, inhibitors of AChE can prevent excessive breakdown of this important neurotransmitter. Monoamine oxidases in the brain are responsible for hydrolyzing important neurotransmitters such as serotonin and dopamine (among others), abnormally rapid hydrolysis of these neurotransmitters via over-activation of monoamine oxidases is associated with several neurodegenerative disorders including anxiety and Parkinson's disease. Herein, we synthesized a focused library of 1,4-dihydropyrimidines (40 compounds) using a deep eutectic solvent and evaluated their potential to inhibit cholinesterase (AChE and BChE) and monoamine oxidase (MAO A and MAO B) enzymes. Several selective and highly potent inhibitors were identified; in silico molecular docking and molecular dynamics simulation studies helped to rationalize the binding site interactions and establish useful structure activity relationship. In silico ADME prediction data identified a few inhibitors that could cross the blood-brain barrier, one such compound was selected for the in vivo estimation of LD50 value and toxicity studies using mice, skin allergy test was also carried out. All in vivo tests and LD50 data established the safety profile of the compound. The results are encouraging enough to further pursue the development of DHPMs as promising multi-target directed ligands against neurodegenerative disorders.