Synthesis, biological evaluation and in silico analysis of new methylxanthine derivatives as potentiators of the cholinergic system.

Abstract

Cholinergic deficiency is commonly associated with several diseases, such as Alzheimer's and Myasthenia Gravis. To address this question, one of the strategies involves the synthesis of hybrid molecules that integrate different pharmacophores. In previous research, caffeine was used as a basis to create caffeine-pyrrolidine hybrids, which were shown to be effective both as acetylcholinesterase (AChE) inhibitors and in potentiating the nicotinic acetylcholine receptor (nAChR). In the present study, a new series of caffeine derivatives with various primary and secondary amines as accessory groups were evaluated. These compounds were efficiently synthesized using a microwave reactor, with alkylbrominated intermediates of theophylline and theobromine as starting reagents along with the corresponding amine. All methylxanthine hybrids were found to be AChE inhibitors, with some exhibiting potency comparable to that of tacrine. To assess the impact of these compounds on the nAChR, fluorescence spectroscopy and single-channel measurements were performed to evaluate their effects on the receptor's conformational state and functionality. Some of the compounds acted as partial agonists, although not all were capable of stabilizing the receptor in a desensitized state. To understand the molecular mechanisms underlying these results, we conducted molecular docking studies on both AChE and nAChR. The agonist activity of the synthesized caffeine analogs on the nAChR was found to depend on the accessory group, while the stabilization of the receptor in a desensitized state was associated with interactions involving the intermediate chain of the hybrid compounds at the binding site. Thus, we obtained a group of molecules that behave as cholinergic potentiators more efficiently than caffeine and also identified key features crucial for modulating the pharmacological targets under study.