The present work concerns the rational design and development of new inhibitors of acetylcholinesterase (AChE) based on the privileged xanthone scaffold. In order to understand and rationalize the mode of action of these target structures a theoretical study was initially conducted. From the results of rational design, a new variety of amphiphilic xanthone derivatives were synthesized, structurally characterized and evaluated as potential anti-Alzheimer agents. The results showed that most of the synthesized compounds exhibited high AChE inhibitory activity at the micromolar range (IC50, 0.46-12.09μM). The synthetic xanthone 11 showed the best inhibitory effect on AChE and a molecular modeling study revealed that 11 targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Therefore, this compound could be considered asa potential lead compound towards new drugs for the treatment of Alzheimer's disease.

Background: Currently approved Alzheimer’s disease medications mainly comprise acetylcholinesterase inhibitors. Many of these inhibitors are either natural compounds or synthetic molecules inspired in natural compounds. Hybrid molecules that can interact with different target sites of the enzyme could lead to the discovery of effective multitarget drugs. Objective: To design, synthesize, and evaluate a series of new aza-resveratrol analogs as in vitro acetyl- and butyrylcholinesterase inhibitors. Methods: The synthesis is achieved by a simple and efficient microwave-assisted method, from commercially available starting materials. Compounds are designed as hybrids of an aza-stilbene nucleus (Schiff base) connected to a tertiary amine by a hydrocarbon chain of variable length, designed to interact both with the peripheric anionic site and the catalytic site of the enzyme. Results: All the derivatives inhibit both enzymes in a concentration-dependent manner, acting as moderate to potent cholinesterase inhibitors. The most potent inhibitors are compounds 12b (IC₅₀ = 0.43 μM) and 12a (IC₅₀ = 0.31 μM) for acetyl- and butyrylcholinesterase, respectively. Compounds 12a and 12b also exhibit significant acetylcholinesterase inhibition in SH-SY5Y human neuroblastoma cells without cytotoxic properties. Enzyme kinetic studies and molecular modeling reveal that inhibitor 12b targets both the catalytic active site and the peripheral anionic site of acetylcholinesterase what makes it able to modulate the self-induced β-amyloid aggregation. Furthermore, the molecular modeling analysis helps to assess the impact of the linker length in the inhibitory activity of this family of new cholinesterase inhibitors. Conclusion: These compounds have the potential to serve as a dual binding site inhibitor and might provide a useful template for the development of new anti-Alzheimer’s disease agents.

Alzheimer9s disease (AD) is a multifactorial neurodegenerative disorder. Since cholinergic deficit is a major factor in this disease, two molecular targets for its treatment are the acetylcholinesterase (AChE) and the nicotinic acetylcholine receptors (nAChRs). Given that caffeine is a natural compound that behaves as an AChE inhibitor and as a partial agonist of nAChRs, the aim of this work was to synthetize more potent bifunctional caffeine analogs that modulate these two molecular targets. To this end, a theophylline structure was connected to a pyrrolidine structure through a methylene chain of different lengths (3 to 7 carbon atoms) to give compounds 7-11. All caffeine derivatives inhibited the AChE, of which compound 11 showed the strongest effect. Electrophysiological studies showed that all compounds behave as agonists of the muscle and the neuronal α7 nAChR with greater potency than caffeine. To explore if the different analogs could affect the nAChR conformational state, the nAChR conformational-sensitive probe crystal violet (CrV) was used. Compounds 9 and 10 conduced the nAChR to a different conformational state comparable with a control nAChR desensitized state. Finally, molecular docking experiments showed that all derivatives interacted with both the catalytic and anionic sites of AChE and with the orthosteric binding site of the nAChR. Thus, the new synthetized compounds can inhibit the AChE and activate muscle and α7 nAChRs with greater potency than caffeine, which suggests that they could be useful leaders for the development of new therapies for the treatment of different neurological diseases. Significance Statement In this work we synthetized caffeine derivatives which can inhibit the AChE and activate both muscle and α7 nAChRs with higher potency than caffeine. These analogs can be divided into two groups: a non-desensitizing and a desensitizing nAChR group. From the nAChR-non desensitizing group, we propose compound 11 as the most interesting analog for further studies since it inhibits AChE with the highest potency and activates the nAChRs in the picomolar range without inducing receptor desensitization.

In the brain of patients with chronic Alzheimer’s disease (AD), the butyrylcholinesterase (BuChE) levels rise while the acetylcholinesterase (AChE) levels decrease. Therefore, development of new selective BuChE inhibitors is of vital importance. Here we present a series of bis(n)‑lophine analogues, where two lophine derivatives are connected by a methylene chain. The bis(n)-lophine analogues were synthesized through one-pot four component reaction between pyridinecarboxaldehydes, 1,n-alkanediamines, benzil, and ammonium acetate. The reactions were performed in a microwave reactor in one step for symmetrical bis(n)-lophines, and in two steps for unsymmetrical bis(n)-lophines. The compounds are strongly selective to BuChE, since none of them inhibit AChE. All the compounds, except 7a, 7b and 7c, displayed potent inhibitory activity against BuChE at a micromolar and sub-micromolar range (half maximal inhibitory concentration (IC50) 32.25-0.03 μM). The enzyme kinetic and docking studies suggests that the inhibitor act as a dual binding site inhibitor, binding into the bottom of the gorge and in the peripheral anionic site (PAS) of BuChE cavity. Furthermore, in vitro studies showed that compounds 5b and 12b had no cytotoxic effects in kidney Vero, hepatic HepG2 and C6 astroglial cell lines.

Methylxanthines and their derivatives are of great interest due to their diverse biological activities. In this work, a new series of twenty-eight semisynthetic theobromine and theophylline derived compounds were designed and synthesized by applying a simple and efficient strategy. First, the corresponding methylxanthine was reacted with a dibromoalkane (n = 3, 5–8) and subsequently, the brominated intermediate was reacted with an amine, including pyrrolidine, piperidine, diethylamine, methylpiperazine, 1-(2-aminoethyl)pyrrolidine, 1-(2-aminoethyl)piperidine, 2-(1-methylpyrrolidin-2-yl)ethanamine, 1-benzylpiperidin-4-amine, 1-benzylpiperidin-4-yl-methanamine, and 2-(1-benzylpiperidin-4-yl)ethan-1-amine. The two synthetic steps were carried out in very short times using a microwave reactor. The biological activity of the new compounds was evaluated on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidases (MAO-A, MAO-B) and beta-secretase (BACE-1). The majority of the new derivatives showed potent and selective in vitro AChE inhibition. Compounds 21, 28 and 30 exhibited the strongest effect on both electric eel and human AChE enzyme, with IC₅₀ values on the low nanomolar scale. The kinetic study of compound 28 in hAChE displayed a mixed inhibition mechanism, suggesting a simultaneous interaction with both the CAS and PAS of the enzyme. This experimental binding mode is consistent with the results of docking and molecular dynamics modelling studies, where it was observed that the piperidinium fragment of 16, 21, 28 and 32 was located at the CAS, whereas the xanthine fragment of each inhibitor interacted with Trp286 in the PAS. These results indicate that these novel xanthine analogues act as selective and potent AChE inhibitors that could also prevent the precipitation of the aberrant Aβ peptide. These properties, in conjunction with their in silico good pharmacokinetic profiles, make these molecules promising lead compounds for the development of new effective drugs against several forms of dementia.