Synthesis and in vitro evaluation of 7-methoxy-N-(pent-4-enyl)-1,2,3,4-tetrahydroacridin-9-amine-new tacrine derivate with cholinergic properties

Synthesis and evaluation of novel arylisoxazoles linked to tacrine moiety: in vitro and in vivo biological activities against Alzheimer's disease

Alzheimer's disease (AD) is now ranked as the third leading cause of death after heart disease and cancer. There is no definite cure for AD due to the multi-factorial nature of the disease, hence, multi-target-directed ligands (MTDLs) have attracted lots of attention. In this work, focusing on the efficient cholinesterase inhibitory activity of tacrine, design and synthesis of novel arylisoxazole-tacrine analogues was developed. In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition assay confirmed high potency of the title compounds. Among them, compounds 7l and 7b demonstrated high activity toward AChE and BChE with IC₅₀ values of 0.050 and 0.039 μM, respectively. Both compounds showed very good self-induced Aβ aggregation and AChE-induced inhibitory activity (79.4 and 71.4% for compound 7l and 61.8 and 58.6% for compound 7b, respectively). Also, 7l showed good anti-BACE1 activity with IC₅₀ value of 1.65 µM. The metal chelation test indicated the ability of compounds 7l and 7b to chelate biometals (Zn²⁺, Cu²⁺, and Fe²⁺). However, they showed no significant neuroprotectivity against Aβ-induced damage in PC12 cells. Evaluation of in vitro hepatotoxicity revealed comparable toxicity of compounds 7l and 7b with tacrine. In vivo studies by Morris water maze (MWM) task demonstrated that compound 7l significantly reversed scopolamine-induced memory deficit in rats. Finally, molecular docking studies of compounds 7l and 7b confirmed establishment of desired interactions with the AChE, BChE, and BACE1 active sites.

Computational Studies on Acetylcholinesterase Inhibitors: From Biochemistry to Chemistry

Acetylcholinesterase inhibitors are the most promising therapeutics for Alzheimer's disease treatment as these prevent the loss of acetylcholine and slows the progression of the disease. The drugs approved for the management of Alzheimer's disease by the FDA are acetylcholinesterase inhibitors but are associated with side effects. Consistent and stringent efforts by the researchers with the help of computational methods opened new ways of developing novel molecules with good acetylcholinesterase inhibitory activity. In this manuscript, we reviewed the studies that identified the essential structural features of acetylcholinesterase inhibitors at the molecular level as well as the techniques like molecular docking, molecular dynamics, quantitative structure-activity relationship, virtual screening, and pharmacophore modelling that were used in designing these inhibitors.

N-alkylated Tacrine Derivatives as Potential Agents in Alzheimer's Disease Therapy

BACKGROUND

Based on the prevalence studies, the number of people suffering from dementia will almost double every 20 years, to 65.7 million in 2030 and 115.4 million in 2050, assuming no changes in mortality, effective preventative measures, definitive diagnostic guidelines or curative treatment. From the abovementioned epidemiological data, it is obvious that dementia constitutes a major public health problem not only at present, but unfortunately also in the future.

OBJECTIVES AND METHODS

Several N-alkylated tacrine (THA) derivatives have already been synthesized by Pomponi et al., in 1997. However, these compounds were tested for their anti-AChE activity using enzyme isolated from Electrophorus electricus. For this reason, we have decided to extend the previously reported series of THA derivatives and consequently test them in the battery of experiments, the results of which have served to more relevant evaluation of these compounds from the perspective of Alzeimer´s disease compared to that published by Pomponi.

RESULTS AND CONCLUSION

In summary, all compounds of interest effectively inhibited ChEs in vitro. One of the most promising derivatives 8 bearing an N-octyl chain showed 2.5-fold higher AChE inhibitory activity in relation to tacrine. With respect to blood-brain barrier (BBB) penetration, it can be claimed that synthesized analogues are presumably able to cross the BBB. From the point of view of hepatotoxicity, selected Nalkylated tacrine derivatives exerted worse results compared to tacrine. However, in vitro results are only illustrative, therefore, only in vivo experiments could determine the real value of selected N-alkylated THA derivatives.

A Systematic Review on Donepezil-based Derivatives as Potential Cholinesterase Inhibitors for Alzheimer’s Disease

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Alzheimer’s Disease (AD) is a multifactorial progressive neurodegenerative disorder characterized by memory loss, disorientation, and gradual deterioration of intellectual capacity. Its etiology has not been elucidated yet. To date, only one therapeutic approach has been approved for the treatment of AD. The pharmacotherapy of AD has relied on noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist - memantine, and acetylcholinesterase (AChE) inhibitors (AChEIs) - tacrine, donepezil, rivastigmine and galantamine. Donepezil was able to ameliorate the symptoms related to AD mainly via AChE, but also through reduction of β-amyloid burden. This review presents the overview of donepezilrelated compounds as potential anti-AD drugs developed on the basis of cholinergic hypothesis to act as solely AChE and butyrylcholinesterase (BChE) inhibitors.

Synthesis and bioevaluation of new tacrine-cinnamic acid hybrids as cholinesterase inhibitors against Alzheimer's disease

Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer's disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure-activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC₅₀ = 10.2 ± 1.2, 16.5 ± 1.7, and 15.3 ± 1.8 nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD.

Development of 2-Methoxyhuprine as Novel Lead for Alzheimer's Disease Therapy

Tacrine (THA), the first clinically effective acetylcholinesterase (AChE) inhibitor and the first approved drug for the treatment of Alzheimer’s disease (AD), was withdrawn from the market due to its side effects, particularly its hepatotoxicity. Nowadays, THA serves as a valuable scaffold for the design of novel agents potentially applicable for AD treatment. One such compound, namely 7-methoxytacrine (7-MEOTA), exhibits an intriguing profile, having suppressed hepatotoxicity and concomitantly retaining AChE inhibition properties. Another interesting class of AChE inhibitors represents Huprines, designed by merging two fragments of the known AChE inhibitors—THA and (−)-huperzine A. Several members of this compound family are more potent human AChE inhibitors than the parent compounds. The most promising are so-called huprines X and Y. Here, we report the design, synthesis, biological evaluation, and in silico studies of 2-methoxyhuprine that amalgamates structural features of 7-MEOTA and huprine Y in one molecule.

Regulating autonomic nervous system homeostasis improves pulmonary function in rabbits with acute lung injury

Background

This study aimed to investigate the effects of regulating autonomic nervous system (ANS) homeostasis by inhibiting sympathetic hyperactivity and/or enhancing parasympathetic activity on pulmonary inflammation and functional disturbance.

Methods

An animal model of acute lung injury (ALI) was established in rabbits by an intratracheal injection of hydrochloric acid (HCl) in rabbits. Animals in control groups were received saline or HCl only, and the others received both HCl and followed treatments: vagus nerve stimulation (VNS), intravenous injection of tetrahydroaminoacridine (THA), or stellate ganglion block (SGB). The effects of different treatments on the changes in autonomic nervous system homeostasis, pulmonary and systemic inflammation, and functional disturbance were detected.

Results

Sympathetic nervous activity was higher than parasympathetic nervous activity in rabbits after HCl aspiration, as demonstrated by the significant changes in the discharge frequency of cervical sympathetic/vagus trunk, and heart rate variability. VNS, THA and SGB could significantly alleviate the changes of ANS induced by HCl aspiration and improved the pulmonary function, especially for SGB treatment.

Conclusions

The disturbance of ANS homeostasis is attributed to a predominance of SNS activity. Administration of VNS, THA and SGB are capable to regulate disequilibrium of the ANS in rabbits with HCl-induced ALI and SGB is supposed to be the most effective approach.

7-Methoxytacrine-p-Anisidine Hybrids as Novel Dual Binding Site Acetylcholinesterase Inhibitors for Alzheimer's Disease Treatment

Alzheimer's disease (AD) is a debilitating progressive neurodegenerative disorder that ultimately leads to the patient's death. Despite the fact that novel pharmacological approaches endeavoring to block the neurodegenerative process are still emerging, none of them have reached use in clinical practice yet. Thus, palliative treatment represented by acetylcholinesterase inhibitors (AChEIs) and memantine are still the only therapeutics used. Following the multi-target directed ligands (MTDLs) strategy, herein we describe the synthesis, biological evaluation and docking studies for novel 7-methoxytacrine-p-anisidine hybrids designed to purposely target both cholinesterases and the amyloid cascade. Indeed, the novel derivatives proved to be effective non-specific cholinesterase inhibitors showing non-competitive AChE inhibition patterns. This compounds' behavior was confirmed in the subsequent molecular modeling studies.

7-Methoxytacrine-adamantylamine heterodimers as cholinesterase inhibitors in Alzheimer's disease treatment--synthesis, biological evaluation and molecular modeling studies

A structural series of 7-MEOTA-adamantylamine thioureas was designed, synthesized and evaluated as inhibitors of human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE). The compounds were prepared based on the multi-target-directed ligand strategy with different linker lengths (n = 2-8) joining the well-known NMDA antagonist adamantine and the hAChE inhibitor 7-methoxytacrine (7-MEOTA). Based on in silico studies, these inhibitors proved dual binding site character capable of simultaneous interaction with the peripheral anionic site (PAS) of hAChE and the catalytic active site (CAS). Clearly, these structural derivatives exhibited very good inhibitory activity towards hBChE resulting in more selective inhibitors of this enzyme. The most potent cholinesterase inhibitor was found to be thiourea analogue 14 (with an IC₅₀ value of 0.47 µM for hAChE and an IC₅₀ value of 0.11 µM for hBChE, respectively). Molecule 14 is a suitable novel lead compound for further evaluation proving that the strategy of dual binding site inhibitors might be a promising direction for development of novel AD drugs.