Increasing Polarity in Tacrine and Huprine Derivatives: Potent Anticholinesterase Agents for the Treatment of Myasthenia Gravis

Structural Insights into the Marine Alkaloid Discorhabdin G as a Scaffold towards New Acetylcholinesterase Inhibitors

In this study, Antarctic Latrunculia sponge-derived discorhabdin G was considered a hit for developing potential lead compounds acting as cholinesterase inhibitors. The hypothesis on the pharmacophore moiety suggested through molecular docking allowed us to simplify the structure of the metabolite. ADME prediction and drug-likeness consideration provided valuable support in selecting 5-methyl-2H-benzo[h]imidazo[1,5,4-de]quinoxalin-7(3H)-one as a candidate molecule. It was synthesized in a four-step sequence starting from 2,3-dichloronaphthalene-1,4-dione and evaluated as an inhibitor of electric eel acetylcholinesterase (eeAChE), human recombinant AChE (hAChE), and horse serum butyrylcholinesterase (BChE), together with other analogs obtained by the same synthesis. The candidate molecule showed a slightly lower inhibitory potential against eeAChE but better inhibitory activity against hAChE than discorhabdin G, with a higher selectivity for AChEs than for BChE. It acted as a reversible competitive inhibitor, as previously observed for the natural alkaloid. The findings from the in vitro assay were relatively consistent with the data available from the AutoDock Vina and Protein-Ligand ANTSystem (PLANTS) calculations.

Design, synthesis, and evaluation of novel bistrifluoromethyl-based hydrazones as dual inhibitors of acetylcholinesterase and carbonic anhydrase enzymes for Alzheimer's disease

In this project, non-sulfonamide bistrifluoromethyl-derived hydrazide-hydrazones were synthesized as multi-target-directed ligands to treat Alzheimer's disease and then, the novel derivatives were characterized by diverse spectral methods. Acetylcholinesterase (AChE), and human carbonic anhydrase (hCA) inhibitory qualifications of these compounds were determined. The reported compounds (2a-y) were determined to be effective inhibitors of the hCA I, hCA II and AChE enzymes with Ki values in the range of 1.130 ± 0.15-5.440 ± 0.93 μM for hCA I, 0.894 ± 0.05-6.647 ± 1.35 μM for hCA II, and 0.196 ± 0.03-4.222 ± 1.04 μM for AChE. In silico studies were also performed to illuminate the binding interactions.

1,2,3-Triazoles in Biomolecular Crystallography: A Geometrical Data-Mining Approach

The 1,2,3-triazole scaffold has become very attractive to identify new chemical entities in drug discovery projects. Despite the widespread use of click chemistry to synthesize numerous 123Ts, there are few drugs on the market that incorporate this scaffold as a substructure. To investigate the true potential of 123Ts in protein-ligand interactions, we examined the noncovalent interactions between the 1,2,3-triazole ring and amino acids in protein-ligand cocrystals using a geometrical approach. For this purpose, we constructed a nonredundant database of 220 PDB IDs from available 123T-protein cocrystal structures. Subsequently, using the Protein Ligand Interaction Profiler web platform (PLIP), we determined whether 1,2,3-triazoles primarily act as linkers or if they can be considered interactive scaffolds. We then manually analyzed the geometrical descriptors from 333 interactions between 1,4-disubstituted 123T rings and amino acid residues in proteins. This study demonstrates that 1,2,3-triazoles exhibit diverse preferred interactions with amino acids, which contribute to protein-ligand binding.

Evaluation of berberine nanoparticles as a strategy to modulate acetylcholinesterase activity

Researchers have concentrated efforts in the search for natural-based reversible inhibitors for cholinesterase enzymes as they may play a key role in the treatment of degenerative diseases. Diverse plant alkaloids can inhibit the action of acetylcholinesterase and, among them, berberine is a promising bioactive. However, berberine has poor water solubility and low bioavailability, which makes it difficult to use in treatment. The solid dispersion technique can improve the water affinity of hydrophobic substances, but berberine solid dispersions have not been extensively studied. Safety testing is also essential to ensure that the berberine-loaded solid dispersions are safe for use. This study investigated the effectiveness of berberine-loaded solid dispersions (SD) as inhibitors of acetylcholinesterase enzyme (AChE). Docking simulation was used to investigate the influence of berberine on AChE, and in vitro assays were conducted to confirm the enzymatic kinetics of AChE in the presence of berberine. Berberine SD also showed improved cytotoxic effects on tumoral cells when dispersed in aqueous media. In vivo assays using Allium cepa were implemented, and no cytotoxicity/genotoxicity was found for the berberine solid dispersion. These results suggest that berberine SD could be a significant step towards safe nanostructures for use in the treatment of neurodegenerative diseases.

Pathogenesis of Alzheimer's Disease and Diversity of 1,2,3-Triazole Scaffold in Drug Development: Design Strategies, Structural Insights, and Therapeutic Potential

Alzheimer's disease is a most prevalent form of dementia all around the globe and currently poses a significant challenge to the healthcare system. Currently available drugs only slow the progression of this disease rather than provide proper containment. Identification of multiple targets responsible for this disease in the last three decades established it as a multifactorial neurodegenerative disorder that needs novel multifunctional agents for its management and the possible reason for the failure of currently available single target clinical drugs. 1,2,3-Triazole is a miraculous nucleus in medicinal chemistry and the first choice for development of multifunctional hybrid molecules. Apart from that, it is an integral component of various drugs in clinical trials as well as in clinical practice. This review is focused on the pathogenesis of Alzheimer's disease and 1,2,3-triazole containing derivatives developed in recent decades as potential anti-Alzheimer's agents. The review will provide (A) precise insight of various established targets of Alzheimer's disease including cholinergic, amyloid, tau, monoamine oxidases, glutamate, calcium, and reactive oxygen species hypothesis and (B) design hypothesis, structure-activity relationships, and pharmacological outcomes of 1,2,3-triazole containing multifunctional anti-Alzheimer's agents. This review will provide a baseline for various research groups working on Alzheimer's drug development in designing potent, safer, and effective multifunctional anti-Alzheimer's candidates of the future.

New Thienobenzo/Naphtho-Triazoles as Butyrylcholinesterase Inhibitors: Design, Synthesis and Computational Study

This study aims to test the inhibition potency of new thienobenzo/naphtho-triazoles toward cholinesterases, evaluate their inhibition selectivity, and interpret the obtained results by molecular modeling. The synthesis of 19 new thienobenzo/naphtho-triazoles by two different approaches resulted in a large group of molecules with different functionalities in the structure. As predicted, most prepared molecules show better inhibition of the enzyme butyrylcholinesterase (BChE), considering that the new molecules were designed according to the previous results. Interestingly, the binding affinity of BChE for even seven new compounds (1, 3, 4, 5, 6, 9, and 13) was similar to that reported for common cholinesterase inhibitors. According to computational study, the active thienobenzo- and naphtho-triazoles are accommodated by cholinesterases through H-bonds involving one of the triazole's nitrogens, π-π stacking between the aromatic moieties of the ligand and aromatic residues of the active sites of cholinesterases, as well as π-alkyl interactions. For the future design of cholinesterase inhibitors and search for therapeutics for neurological disorders, compounds with a thienobenzo/naphtho-triazole skeleton should be considered.

Indole diketopiperazine alkaloids and aromatic polyketides from the Antarctic fungus Penicillium sp. SCSIO 05705

A new indole diketopiperazine alkaloid, named penilline D (1), together with five known indole alkaloid analogues (2-5, 11), two meroterpenoids (6 and 12), and four butenolide derivatives (7-10), were isolated from the Antarctic fungus Penicillium sp. SCSIO 05705. Extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation were used to elucidate the structure of penilline D (1), including its absolute configuration. All isolated compounds (1-12) were evaluated for their cytotoxic, antibacterial and enzyme inhibitory activities against acetylcholinesterase (AChE) and pancreatic lipase (PL). Among them, compound 5 exhibited moderate in vitro cytotoxic activity against the 143B cell line with IC₅₀ value of 12.64 ± 0.78 μM. Compound 6 showed strong inhibitory activity against AChE with IC₅₀ value of 0.36 nM (IC₅₀ 18.7 nM for Tacrine), while compounds 6 and 11 showed weak PL enzyme inhibitory activity. Furthermore, an in silico molecular docking study was also performed between 6 and AChE.

Inhibition of Toxoplasma gondii by 1,2,4-triazole-based compounds: marked improvement in selectivity relative to the standard therapy pyrimethamine and sulfadiazine

A safer treatment for toxoplasmosis would be achieved by improving the selectivity profile of novel chemotherapeutics compared to the standard therapy pyrimethamine (PYR) and sulfadiazine (SDZ). We previously reported on the identification of the compounds with imidazole-thiosemicarbazide scaffold as potent and selective anti-Toxoplasma gondii (T. gondii) agents. In our current research, we report on the optimisation of this chemical scaffold leading to the discovery cyclic analogue 20 b with s-triazole core structure. This compound displayed prominent CC₃₀ to IC₅₀ selectivity index (SI) of 70.72, making it 160-fold more selective than SDZ, 11-fold more selective than PYR, and 4-fold more selective than trimethoprim (TRI). Additionally, this compound possesses prerequisite drug-like anti-Toxoplasma properties to advance into preclinical development; it showed ability to cross the BBB, did not induce genotoxic and haemolytic changes in human cells, and as well as it was characterised by low cellular toxicity.

Assessments of Ceanothanes Triterpenes as Cholinesterase Inhibitors: An Investigation of Potential Agents with Novel Inspiration for Drug Treatment of Neurodegenerative Diseases

The purpose of this study was to determine the inhibitory capacity of ceanothanes triterpenes isolate from Chilean Rhamnaceae on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. Seven ceanothanes triterpenes were isolated from aerial parts of plant material by classical phytochemical methods or prepared by the hemisynthetic method. Structures were determined by the spectroscopic method (1H-NMR and 13C NMR) and mass spectrometry (MS). AChE and BChE activity were determined by the Ellmann method for all compounds. All tested compounds exerted a greater affinity to AChE than to BChE, where compound 3 has an IC50 of 0.126 uM for AChE and of >500 uM to BChE. Kinetic studies indicated that its inhibition was competitive and reversible. According to the molecular coupling and displacement studies of the propidium iodide test, the inhibitory effect of compound 3 would be produced by interaction with the peripheral anionic site (PAS) of AChE. The compounds tested (1−7) showed an important inhibitory activity of AChE, binding to PAS. Therefore, inhibitors that bind to PAS would prevent the formation of the AChE-Aβ complex, constituting a new alternative in the treatment of Alzheimer’s disease (AD).

Synthesis and cholinesterase inhibitory activity study of Amaryllidaceae alkaloid analogues with N-methyl substitution

Polycyclic compounds with N-methyl substitution, structurally related to Amaryllidaceae alkaloids, have been synthesised, together with their analogues bearing a quaternary nitrogen atom. To prevent the lone electron pair of the nitrogen from interfering with the reaction sequence, two approaches to the synthesis were investigated: N-oxidation and Boc protection of the nitrogen. The second method was more successful due to the limited stability of N-oxides in the halocyclisation step. An asymmetric version of the synthesis was also developed for this type of compounds. The prepared products were tested in vitro for their cholinesterase inhibitory activity and the results were rationalised by molecular docking studies with human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBuChE). In general, our products were more active against BuChE than against AChE, and it was noted that larger ligands should be prepared for future studies, since in some cases acetylcholine can still fit into the active site along with the bound ligand.

In Vitro and In Silico Evaluation of Cholinesterase Inhibition by Alkaloids Obtained from Branches of Abuta panurensis Eichler

Alkaloids are natural products known as ethnobotanicals that have attracted increasing attention due to a wide range of their pharmacological properties. In this study, cholinesterase inhibitors were obtained from branches of Abuta panurensis Eichler (Menispermaceae), an endemic species from the Amazonian rainforest. Five alkaloids were isolated, and their structure was elucidated by a combination of 1D and 2D 1H and 13C NMR spectroscopy, HPLC-MS, and high-resolution MS: Lindoldhamine isomer m/z 569.2674 (1), stepharine m/z 298.1461 (2), palmatine m/z 352.1616 (3), 5-N-methylmaytenine m/z 420.2669 (4) and the N-trans-feruloyltyramine m/z 314.1404 (5). The compounds 1, 3, and 5 were isolated from A. panurensis for the first time. Interaction of the above-mentioned alkaloids with acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes was investigated in silico by molecular docking and molecular dynamics. The molecules under investigation were able to bind effectively with the active sites of the AChE and BChE enzymes. The compounds 1–4 demonstrated in vitro an inhibitory effect on acetylcholinesterase with IC50 values in the range of 19.55 µM to 61.24 µM. The data obtained in silico corroborate the results of AChE enzyme inhibition.

Bisabolanoic acid A, a new polychiral sesquiterpene with AChE inhibitory activity from a mangrove-derived fungus Colletotrichum sp

A new polychiral bisabolane sesquiterpene, bisabolanoic acid A (1), was isolated from the mangrove-derived fungus Colletotrichum sp. SCSIO KcB3-2. Its planar structure was identified on the basis of spectroscopic data analysis (HRESIMS, 1D, and 2D NMR), and the absolute configurations of three chiral carbons were determined by experimental and calculated electronic circular dichroism (ECD) and optical rotatory dispersion (ORD), together with Mo₂(OAc)₄-induced ECD methods. Bisabolanoic acid A (1) showed moderate inhibitory activity against acetylcholinesterase (AChE) with IC₅₀ value of 2.2 μM, and the in silico molecular docking was also performed.

Effects of Natural Products on Neuromuscular Junction

Neuromuscular junction (NMJ) disorders result from damage, malfunction or absence of one or more key proteins involved in neuromuscular transmission, comprising a wide range of disorders. The most common pathology is antibody-mediated or downregulation of ion channels or receptors, resulting in Lambert-Eaton myasthenic syndrome, myasthenia gravis, and acquired neuromyotonia (Isaac's syndrome), and rarely congenital myasthenic syndromes caused by mutations in NMJ proteins. A wide range of symptomatic treatments, immunomodulating therapies, or immunosuppressive drugs have been used to treat NMJ diseases. Future research must be directed at better understanding of the pathogenesis of these diseases, and developing novel disease-specific treatments. Numerous secondary metabolites, especially alkaloids isolated from plants have been used to treat NMJ diseases in traditional and clinical practices. An ethnopharmacological approach has provided leads for identifying new treatment for NMJ diseases. In this review, we performed a literature survey in Pubmed, Science Direct, and Google Scholar to gather information on drug discovery from plant sources for NMJ disease treatments. To date, most research has focused on the effect of herbal remedies on cholinesterase inhibitory and antioxidant activities. This review provides leads for identifying potential new drugs from plant sources for the treatment of NMJ diseases.

Curating the gnomAD database: Report of novel variants in the thyrogobulin gene using in silico bioinformatics algorithms

Thyroglobulin (TG) is a large glycosylated protein of 2767 amino acids, secreted by the thyrocytes into the follicular lumen. It plays an essential role in the process of thyroid hormone synthesis. TG gene variants lead to permanent congenital hypothyroidism. In the present work, we report a detailed population and bioinformatic prediction analyses of the TG variants indexed in the Genome Aggregation Database (gnomAD). The results showed a clear predominance of nonsense variants in the European (Finnish), European (Non-Finnish) and Ashkenazi Jewish ethnic groups, whereas the splice site variants predominate in South Asian and African/African-American populations. In total, 282 novel TG variants were described (47 missense involving the wild-type cysteine residues, 177 missense located in the ChEL domain and 58 splice site variants) which were not reported in the literature and that would have deleterious effects in prediction programs. In the gnomAD population, the estimated prevalence of heterozygous carriers of the potentially damaging variants was 1:320. In conclusion, we provide an updated and curated reference source for the diagnosis of thyroid disease, mainly to congenital hypothyroidism due to TG deficiency. The identification and characterization of TG variants is undoubtedly a valuable approach to study the TG structure/function relations and an important tool for clinical diagnosis and genetic counseling.

Effect of Chronic Administration of 5-(3-chlorophenyl)-4-Hexyl-2,4 -Dihydro-3H-1,2,4-Triazole-3-Thione (TP-315)-A New Anticonvulsant Drug Candidate-On Living Organisms

About 70 million people suffer from epilepsy—a chronic neurodegenerative disease. In most cases, the cause of the disease is unknown, but epilepsy can also develop as the result of a stroke, trauma to the brain, or the use of psychotropic substances. The treatment of epilepsy is mainly based on the administration of anticonvulsants, which the patient must most often use throughout their life. Despite significant progress in research on antiepileptic drugs, about 30% of patients still have drug-resistant epilepsy, which is insensitive to pharmacotherapy used so far. In our recent studies, we have shown that 4-alkyl-5-aryl-1,2,4-triazole-3-thiones act on the voltage-gated sodium channels and exhibit anticonvulsant activity in an MES (maximal electroshock-induced seizure) and 6Hz test in mice. Previous studies have shown their beneficial toxic and pharmacological profile, but their effect on a living organism during chronic use is still unknown. In the presented study, on the basis of the previously conducted tests and the PAMPA (parallel artificial membrane permeability assay) BBB (blood–brain barrier) test, we selected one 1,2,4-triazole-3-thione derivative—TP-315—for further studies aimed at assessing the impact of its chronic use on a living organism. After long-term administration of TP-315 to Albino Swiss mice, its effect on the functional parameters of internal organs was assessed by performing biochemical, morphological, and histopathological examinations. It was also determined whether the tested compound inhibits selected isoforms of the CYP450 enzyme system. On the basis of the conducted tests, it was found that TP-315 does not show nephrotoxic nor hepatotoxic effects and does not cause changes in hematological parameters. In vitro tests showed that TP-315 did not inhibit CYP2B6, CYP2D6, CYP3A4, or CYP3A5 enzymes at the concentration found in the serum of mice subjected to long-term exposure to this compound.

Tyrosol 1,2,3-triazole analogues as new acetylcholinesterase (AChE) inhibitors

The present work proposed the preparation of triazolic analogues of tyrosol, a biophenol found in olive oil and whose wide range of bioactivities has been the target of many studies. We obtained fifteen novel tyrosol derivatives and the compounds of the series were later evaluated as acetylcholinesterase (AChE) inhibitors. The study of AChE inhibition is important for the development of new drugs and pesticides, and especially the research for managing Alzheimer's disease. The most active compound, namely 7-({1-[2-(4-hydroxyphenyl)ethyl]-1H-1,2,3-triazol-4-yl}methoxy)-4-methyl-2H-chromen-2-one (30), showed IC₅₀ value of 14.66 ± 2.29 μmol L^-1. Docking experiments corroborated by kinetic assay are suggestive of a competitive inhibition mechanism. Derivatives interacted with amino acids from the AChE active site associated to the development of Alzheimer's disease. The results indicate that the compounds synthesized have a high potential as prototypes for the development of new acetylcholinesterase inhibitors.

Structural Isomerism and Enhanced Lipophilicity of Pyrithione Ligands of Organoruthenium(II) Complexes Increase Inhibition on AChE and BuChE

The increasing number of Alzheimer’s disease (AD) cases requires the development of new improved drug candidates, possessing the ability of more efficient treatment as well as less unwanted side effects. Cholinesterase enzymes are highly associated with the development of AD and thus represent important druggable targets. Therefore, we have synthesized eight organoruthenium(II) chlorido complexes 1a–h with pyrithione-type ligands (pyrithione = 1-hydroxypyridine-2(1H)-thione, a), bearing either pyrithione a, its methyl (b-e) or bicyclic aromatic analogues (f–h) and tested them for their inhibition towards electric eel acetylcholinesterase (eeAChE) and horse serum butyrylcholinesterase (hsBuChE). The experimental results have shown that the novel complex 1g with the ligand 1-hydroxyquinoline-2-(1H)-thione (g) improves the inhibition towards eeAChE (IC₅₀ = 4.9 μM) and even more potently towards hsBuChE (IC₅₀ = 0.2 μM) in comparison with the referenced 1a. Moreover, computational studies on Torpedo californica AChE have supported the experimental outcomes for 1g, possessing the lowest energy value among all tested complexes and have also predicted several interactions of 1g with the target protein. Consequently, we have shown that the aromatic ring extension of the ligand a, though only at the appropriate position, is a viable strategy to enhance the activity against cholinesterases.

CdTe QD-based inhibition and reactivation assay of acetylcholinesterase for the detection of organophosphorus pesticides

An enzyme immobilized glutathione (GSH)-capped CdTe quantum dot (QD)-based fluorescence assay has been developed for monitoring organophosphate pesticides.

Preclinical evaluation of 1,2,4-triazole-based compounds targeting voltage-gated sodium channels (VGSCs) as promising anticonvulsant drug candidates

Epilepsy is a chronic neurological disorder affecting nearly 65-70 million people worldwide. Despite the observed advances in the development of new antiepileptic drugs (AEDs), still about 30-40% of patients cannot achieve a satisfactory seizure control. In our current research, we aimed at using the combined results of radioligand binding experiments, PAMPA-BBB assay and animal experimentations in order to design a group of compounds that exhibit broad spectrum of anticonvulsant activity. The synthesized 4-alkyl-5-substituted-1,2,4-triazole-3-thione derivatives were primarily screened in the maximal electroshock-induced seizure (MES) test in mice. Next, the most promising compounds (17, 22) were investigated in 6 Hz (32 mA) psychomotor seizure model. Protective effect of compound 22 was almost similar to that of levetiracetam. Moreover, these compounds did not induce genotoxic and hemolytic changes in human cells as well as they were characterized by low cellular toxicity. Taking into account the structural requirements for good anticonvulsant activity of 4-alkyl-5-aryl-1,2,4-triazole-3-thiones, it is visible that small electron-withdrawing substituents attached to phenyl ring have beneficial effects both on affinity towards VGSCs and protective activity in the animal models of epilepsy.

Two New AChE Inhibitors Isolated from Li Folk Herb Heilaohu "Kadsura coccinea" Stems

Two new triterpenoids, named kadsuricoccins A and B, together with three known ones, were isolated from the Li folk herb Heilaohu, the stems of Kadsura coccinea (Lem.) A. C. Smith, which was used for food and as a healthy supplement. Their structures were elucidated by comprehensive analyses of mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic data. To search healthy components, an acetylcholinesterase (AChE) inhibitory activity test by Ellman’s Method was conducted, kadsuricoccins A and B showed activity with the AChE inhibit index (AII) up to 68.96% ± 0.19% and 57.8% ± 0.11% at 94 nM (compared with positive control tacrine AII 79.80% ± 0.20%, 9.4 nM), respectively.

Chlorinated tacrine analogs: Design, synthesis and biological evaluation of their anti-cholinesterase activity as potential treatment for Alzheimer's disease

In search of potent acetyl cholinesterase inhibitors with low hepatotoxicity for the treatment of Alzheimer's disease, introduction of a chloro substitution to tacrine and some of its analogs has proven to be beneficial in maintaining or potentiating the cholinesterase inhibitory activity. Furthermore, it was found to be able to reduce the hepatotoxicity of the synthesized compounds, which is the main target of the study. Accordingly, a series of new 4-(chlorophenyl)tetrahydroquinoline derivatives, was synthesized and characterized. The synthesized compounds were evaluated for their in vitro and in vivo anti-cholinesterase activity using tacrine as a reference standard. Furthermore, they were investigated for their hepatotoxicity compared to tacrine. The obtained biological results revealed that all synthesized compounds displayed equivalent or significantly higher anti-cholinesterase activity and lower hepatotoxicity in comparison to tacrine. In addition, in silico drug-likeness of the synthesized compounds were predicted and their practical logP were assessed indicating that all synthesized compounds can be considered as promising hits/leads. Furthermore, docking study of the compound showing the highest in vitro anticholinesterase activity was performed and its binding mode was compared to that of tacrine.

Design and evaluation of selective butyrylcholinesterase inhibitors based on Cinchona alkaloid scaffold

This paper describes the synthesis and anticholinesterase potency of Cinchona-based alkaloids; ten quaternary derivatives of cinchonines and their corresponding pseudo-enantiomeric cinchonidines. The quaternization of quinuclidine moiety of each compound was carried out with groups diverse in their size: methyl, benzyl and differently meta- and para-substituted benzyl groups. All of the prepared compounds reversibly inhibited human butyrylcholinesterase and acetylcholinesterase with Ki constants within nanomolar to micromolar range. Five cinchonidine derivatives displayed 95-510 times higher inhibition selectivity to butyrylcholinesterase over acetylcholinesterase and four were potent butyrylcholinesterase inhibitors with Ki constants up to 100 nM, of which N-para-bromobenzyl cinchonidinium bromide can be considered a lead for further modifications and optimizations for possible use in the treatment of neurodegenerative diseases.