New Multitarget Molecules Derived from Caffeine as Potentiators of the Cholinergic System.

Cholinergic deficit is a characteristic factor of several pathologies, such as myasthenia gravis, some types of congenital myasthenic syndromes, and Alzheimer's Disease. Two molecular targets for its treatment are acetylcholinesterase (AChE) and nicotinic acetylcholine receptor (nAChR). In previous studies, we found that caffeine behaves as a partial nAChR agonist and confirmed that it inhibits AChE. Here, we present new bifunctional caffeine derivatives consisting of a theophylline ring connected to amino groups by different linkers. All of them were more potent AChE inhibitors than caffeine. Furthermore, although some of them also activated muscle nAChR as partial agonists, not all of them stabilized nAChR in its desensitized conformation. To understand the molecular mechanism underlying these results, we performed docking studies on AChE and nAChR. The nAChR agonist behavior of the compounds depends on their accessory group, whereas their ability to stabilize the receptor in a desensitized state depends on the interactions of the linker at the binding site. Our results show that the new compounds can inhibit AChE and activate nAChR with greater potency than caffeine and provide further information on the modulation mechanisms of pharmacological targets for the design of novel therapeutic interventions in cholinergic deficit.

Naturally Occurring Cholinesterase Inhibitors from Plants, Fungi, Algae, and Animals: A Review of the Most Effective Inhibitors Reported in 2012-2022.

Since the development of the "cholinergic hypothesis" as an important therapeutic approach in the treatment of Alzheimer's disease (AD), the scientific community has made a remarkable effort to discover new and effective molecules with the ability to inhibit the enzyme acetylcholinesterase (AChE). The natural function of this enzyme is to catalyze the hydrolysis of the neurotransmitter acetylcholine in the brain. Thus, its inhibition increases the levels of this neurochemical and improves the cholinergic functions in patients with AD alleviating the symptoms of this neurological disorder. In recent years, attention has also been focused on the role of another enzyme, butyrylcholinesterase (BChE), mainly in the advanced stages of AD, transforming this enzyme into another target of interest in the search for new anticholinesterase agents. Over the past decades, Nature has proven to be a rich source of bioactive compounds relevant to the discovery of new molecules with potential applications in AD therapy. Bioprospecting of new cholinesterase inhibitors among natural products has led to the discovery of an important number of new AChE and BChE inhibitors that became potential lead compounds for the development of anti-AD drugs. This review summarizes a total of 260 active compounds from 142 studies which correspond to the most relevant (IC 50 ≤ 15 µM) research work published during 2012-2022 on plant-derived anticholinesterase compounds, as well as several potent inhibitors obtained from other sources like fungi, algae, and animals.

New Synthetic Caffeine Analogs as Modulators of the Cholinergic System.

Alzheimer's disease 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 whether 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 neurologic diseases. SIGNIFICANCE STATEMENT: In this work we synthetized caffeine derivatives which can inhibit acetylcholinesterase and activate both muscle and α7 nicotinic acetylcholine receptors (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 acetylcholinesterase with the highest potency and activates the nAChRs in the picomolar range without inducing receptor desensitization.

Design and Microwave-Assisted Synthesis of Aza-Resveratrol Analogs with Potent Cholinesterase Inhibition.

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 ß-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.

Design, synthesis and biological evaluation of 1,3-dihydroxyxanthone derivatives: Effective agents against acetylcholinesterase.

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.