New Pyrimidine and Pyridine Derivatives as Multitarget Cholinesterase Inhibitors: Design, Synthesis, and in Vitro and in Cellulo Evaluation

A new series of pyrimidine and pyridine diamines was designed as dual binding site inhibitors of cholinesterases (ChEs), characterized by two small aromatic moieties separated by a diaminoalkyl flexible linker. Many compounds are mixed or uncompetitive acetylcholinesterase (AChE) and/or butyrylcholinesterase (BChE) nanomolar inhibitors, with compound 9 being the most active on Electrophorus electricus AChE (EeAChE) (Ki = 0.312 μM) and compound 22 on equine BChE (eqBChE) (Ki = 0.099 μM). Molecular docking and molecular dynamic studies confirmed the interaction mode of our compounds with the enzymatic active site. UV-vis spectroscopic studies showed that these compounds can form complexes with Cu2+ and Fe3+ and that compounds 18, 20, and 30 have antioxidant properties. Interestingly, some compounds were also able to reduce Aβ42 and tau aggregation, with compound 28 being the most potent (22.3 and 17.0% inhibition at 100 μM on Aβ42 and tau, respectively). Moreover, the most active compounds showed low cytotoxicity on a human brain cell line and they were predicted as BBB-permeable.