Novel 2-aminopyrimidine carboxamide derivatives as potential anti-Alzheimer's disease agents: Design, synthesis, biological activity and computational simulation evaluation

In this study, a series of 2-amino-5-formamidopyrimidine derivatives were designed and synthesized. Their potential as cholinesterase inhibitors (ChEIs) for the treatment of Alzheimer's disease (AD) were evaluated by the Ellman method. Meanwhile, the antioxidant activity of these compounds were assessed by the DPPH (2,2-diphen-yl-1-picrylhydrazyl) free radical scavenging assay. The cholinesterase (ChE) inhibition test showed that most compounds exhibited excellent to moderate inhibitory effects on acetylcholinesterase (AChE), while most of them did not show significant inhibitory effects on butyrylcholinesterase (BuChE), demonstrating significant selectivity. Among them, compound 9 s (AChE: IC₅₀ = 1.60 μM) whose AChE inhibitory activity is superior to the positive control galantamine (AChE: IC₅₀ = 5.10 μM) is the most promising representative compound. Meanwhile, compound 9 s has high selectivity with a SI (IC₅₀ ratio of BuChE to AChE) value of 29.85. The results of enzyme kinetics study determined that compound 9 s was a mixed-type inhibitor. Additionally, the molecular docking studies results indicated that compound 9 s could simultaneously interact with the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE, which was consistent with the results of the enzyme kinetics experiments. Molecular dynamics (MD) simulation study further verified the stability of the 9 s-AChE complex. In addition, the DPPH radical scavenging assay indicated that these compounds also possessed relatively weak antioxidant activities. Among them, compound 9p exhibited the best antioxidant activity with an IC₅₀ value of 113.93 μM, which was lower than that of the positive control ascorbic acid (IC₅₀ = 41.17 μM). Overall, these experimental results suggested that compound 9 s as AChE Inhibitor had potential value for further research.