Development of an in-vivo active reversible butyrylcholinesterase inhibitor

Novel anti-neuroinflammatory pyranone-carbamate derivatives as selective butyrylcholinesterase inhibitors for treating Alzheimer's disease

Butyrylcholinesterase (BuChE) and neuroinflammation have recently emerged as promising therapeutic directions for Alzheimer's disease (AD). Herein, we synthesised 19 novel pyranone-carbamate derivatives and evaluated their activities against cholinesterases and neuroinflammation. The optimal compound 7p exhibited balanced BuChE inhibitory activity (eqBuChE IC50 = 4.68 nM; huBuChE IC50 = 9.12 nM) and anti-neuroinflammatory activity (NO inhibition = 28.82% at 10 μM, comparable to hydrocortisone). Enzyme kinetic and docking studies confirmed compound 7p was a mix-type BuChE inhibitor. Additionally, compound 7p displayed favourable drug-likeness properties in silico prediction, and exhibited high BBB permeability in the PAMPA-BBB assay. Compound 7p had good safety in vivo as verified by an acute toxicity assay (LD50 > 1000 mg/kg). Most importantly, compound 7p effectively mitigated cognitive and memory impairments in the scopolamine-induced mouse model, showing comparable effects to Rivastigmine. Therefore, we envisioned that compound 7p could serve as a promising lead compound for treating AD.

Novel carbazole-oxadiazole derivatives as anti-α-glucosidase and anti-α-amylase agents: Design, synthesis, molecular docking, and biological evaluation

To find novel inhibitors of α-glucosidase and α-amylase, a series of new carbazole-oxadiazole derivatives (6a-6n) were prepared, and screened for their anti-α-glucosidase and anti-α-amylase effects. Most of the tested derivatives showed different degrees of α-glucosidase and α-amylase inhibitory activity (IC50: 21.39 ± 0.69-92.05 ± 1.54 μM, 45.53 ± 1.50-126.14 ± 6.33 μM, respectively) compared to the standard acarbose (IC50: 427.00 ± 9.56 μM, 24.68 ± 1.10 μM, respectively). Thereinto, 6c (IC50 = 21.39 ± 0.69 μM) displayed the most effective anti-α-glucosidase activity and 6e presented the best anti-α-amylase activity with an IC50 value of 45.53 ± 1.50 μM. Lineweaver-Burk plot analysis suggested that 6c and 6e behaved as mixed α-glucosidase inhibitor and mixed α-amylase inhibitor, respectively. The results of circular dichroism, atomic force microscope, and molecular docking simulation exposed interaction mechanisms between two preferred compounds (6c and 6e) and their corresponding enzymes. Combined with the possible properties of reducing the elevation in postprandial blood glucose, oral activity, positive bioavailability, and low cytotoxicity of 6c and 6e, it could be concluded that the target derivatives may be able to act as lead molecules for the development of new hypoglycemic agents.

Benzimidazole and Benzoxazole Derivatives Against Alzheimer's Disease

Benzimidazole and benzoxazole derivatives are included in the category of medical drugs in a wide range of areas such as anticancer, anticoagulant, antihypertensive, anti- inflammatory, antimicrobial, antiparasitic, antiviral, antioxidant, immunomodulators, proton pump inhibitors, hormone modulators, etc. Many researchers have focused on synthesizing more effective benzimidazole and benzoxazole derivatives for screening various biological activities. In addition, there are benzimidazole and benzoxazole rings as bioisosteres of aromatic rings found in drugs used in the treatment of Alzheimer's disease. Because of the diverse activity of the benzimidazole and benzoxazole rings and bioisosteres marketed as drugs for Alzheimer Diseases, designed compounds containing these rings are likely to be effective against Alzheimer's disease. In this study, the effectiveness of compounds containing benzimidazole and benzoxazole rings against Alzheimer's disease will be examined.

The selective butyrylcholinesterase inhibitor UW-MD-95 shows symptomatic and neuroprotective effects in a pharmacological mouse model of Alzheimer's disease

AIMS

Alzheimer's disease (AD) is a devastating dementia characterized by extracellular amyloid-β (Aβ) protein aggregates and intracellular tau protein deposition. Clinically available drugs mainly target acetylcholinesterase (AChE) and indirectly sustain cholinergic neuronal tonus. Butyrylcholinesterase (BChE) also controls acetylcholine (ACh) turnover and is involved in the formation of Aß aggregates and senile plaques. UW-MD-95 is a novel carbamate-based compound acting as a potent pseudo-irreversible BChE inhibitor, with high selectivity versus AChE, and showing promising protective potentials in AD.

METHODS

We characterized the neuroprotective activity of UW-MD-95 in mice treated intracerebroventricularly with oligomerized Aβ25-35 peptide using behavioral, biochemical, and immunohistochemical approaches.

RESULTS

When injected acutely 30 min before the behavioral tests (spontaneous alternation in the Y-maze, object recognition, or passive avoidance), UW-MD-95 (0.3-3 mg/kg) showed anti-amnesic effects in Aβ25-35-treated mice. When injected once a day over 7 days, it prevented Aβ25-35-induced memory deficits. This effect was lost in BChE knockout mice. Moreover, the compound prevented Aβ25-35-induced oxidative stress (assessed by lipid peroxidation or cytochrome c release), neuroinflammation (IL-6 and TNFα levels or GFAP and IBA1 immunoreactivity) in the hippocampus and cortex, and apoptosis (Bax level). Moreover, UW-MD-95 significantly reduced the increase in soluble Aβ1-42 level in the hippocampus induced by Aβ25-35.

CONCLUSION

UW-MD-95 appeared as a potent neuroprotective compound in the Aβ25-35 model of AD, with potentially an impact on Aβ1-42 accumulation that could suggest a novel mechanism of neuroprotection.

Indole-Based Compounds in the Development of Anti-Neurodegenerative Agents

Neurodegeneration is a gradual decay process leading to the depletion of neurons in both the central and peripheral nervous systems, ultimately resulting in cognitive dysfunctions and the deterioration of brain functions, alongside a decline in motor skills and behavioral capabilities. Neurodegenerative disorders (NDs) impose a substantial socio-economic strain on society, aggravated by the advancing age of the world population and the absence of effective remedies, predicting a negative future. In this context, the urgency of discovering viable therapies is critical and, despite significant efforts by medicinal chemists in developing potential drug candidates and exploring various small molecules as therapeutics, regrettably, a truly effective treatment is yet to be found. Nitrogen heterocyclic compounds, and particularly those containing the indole nucleus, which has emerged as privileged scaffold, have attracted particular attention for a variety of pharmacological applications. This review analyzes the rational design strategy adopted by different research groups for the development of anti-neurodegenerative indole-based compounds which have the potential to modulate various molecular targets involved in NDs, with reference to the most recent advances between 2018 and 2023.

Disentangling the formation, mechanism, and evolvement of the covalent methanesulfonyl fluoride acetylcholinesterase adduct: Insights into an aged-like inactive complex susceptible to reactivation by a combination of nucleophiles

Chemical warfare nerve agents and pesticides, known as organophosphorus compounds inactivate cholinesterases (ChEs) by phosphorylating the serine hydroxyl group located at the active site of ChEs. Over the course of time, phosphorylation is followed by loss of an organophosphate-leaving group and the bond with ChEs becomes irreversible, a process known as aging. Differently, structurally related irreversible catalytic poisons bearing sulfur instead of phosphorus convert ChEs in its aged form only by covalently binding to the key catalytic serine. Kinetic and crystallographic studies of the interaction between Torpedo californica acetylcholinesterase (TcAChE) and a small organosulfonate, methanesulfonyl fluoride (MSF), indeed revealed irreversibly methylsulfonylated serine 200, to be isosteric with the bound aged sarin/soman analogues. The potent bulky reversible inhibitor 7-bis-tacrine (BTA) adopts, in the active site of the crystal structure of the MSF-enzyme adduct, a location and an orientation that closely resemble the one being found in the crystal structure of the BTA-enzyme complex. Remarkably, the presence of BTA accelerates the rate of methanesulfonylation by a factor of two. This unexpected result can be explained on the basis of two facts: i) the steric hindrance exerted by BTA to MSF in accessing the active site and ii) the acceleration of the MSF-enzyme adduct formation as a consequence of the lowering of the rotational and translational degrees of freedom in the proximity of the catalytic serine. It is well known that pralidoxime (2-Pyridine Aldoxime Methyl chloride, 2-PAM) alone or in the presence of the substrate acetylcholine cannot reactivate the active site serine of the TcAChE-MSF adduct. We show that the simultaneous presence of 2-PAM and the additional neutral oxime, 2-[(hydroxyimino)methyl]-l-methylimidazol (2-HAM), triggers the reactivation process of TcAChE within the hour timescale. Overall, our results pave the way toward the likely use of a cocktail of distinctive oximes as a promising recipe for an effective and fast reactivation of aged cholinesterases.

Butyrylcholinesterase-Activated Near-Infrared Fluorogenic Probe for In Vivo Theranostics of Alzheimer's Disease

Butyrylcholinesterase (BChE) is a promising biomarker and effective therapeutic target for Alzheimer's disease (AD). Herein, we designed a BChE-activated near-infrared (NIR) probe, DTNP, which could be activated by BChE and inhibit its enzymatic activity. DTNP is composed of a cyclopropane moiety as the recognition unit, a NIR fluorophore hemicyanine as the NIR reporter, and a BChE inhibitor as the therapeutic unit. DTNP specifically binds BChE with high sensitivity and exhibits strong "turn-on" NIR fluorescence as well as nerve cell protection. In vivo imaging shows DTNP has favorable blood-brain barrier permeability and long-term tracking ability with preliminary competence in AD diagnosis. DTNP can significantly inhibit BChE activity, promote the release of ACh, and rescue learning deficits and cognitive impairment. Therefore, DTNP, the first reported and partially validated theranostic probe for the detection of BChE in AD, may provide a foundation and inspiration for imaging and therapy in AD.

Machine learning-based virtual screening and molecular modelling studies for identification of butyrylcholinesterase inhibitors as anti-Alzheimer's agent

Butyrylcholinesterase (BChE) is a hydrolase involved in the metabolism and detoxification of specific esters in the blood. It is also implicated in the progression of Alzheimer's disease, a type of dementia. As the disease progresses, the level of BChE tends to increase, opting for a major role as an acetylcholine-degrading enzyme and surpassing the role of acetylcholinesterase. Hence, the development of BChE inhibitors could be beneficial for the latter stages of the disease. In the present study, machine learning (ML) models were developed and employed to identify new BChE inhibitors. Further, the identified molecules were subjected to molecular property filters. The filtered ligands were studied through molecular modelling techniques, viz. molecular docking and molecular dynamics (MD). Support vector machine-based ML models resulted in the identification of 3291 compounds that would have predicted IC50 values less than 200 nM. The docking study showed that compounds ART13069594, ART17350769 and LEG19710163 have mean binding energies of -9.62, -9.26 and -8.93 kcal/mol, respectively. The MD study displayed that all the selected ligands showed stable complexes with BChE. The trajectories of all the ligands were stable similar to the standard BChE inhibitors.Communicated by Ramaswamy H. Sarma.

Design, synthesis, and biological evaluation of novel capsaicin-tacrine hybrids as multi-target agents for the treatment of Alzheimer's disease

A series of novel hybrid compounds were designed, synthesized, and utilized as multi-target drugs to treat Alzheimer's disease (AD) by connecting capsaicin and tacrine moieties. The biological assays indicated that most of these compounds demonstrated strong inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities with IC50 values in the nanomolar, as well as good blood-brain barrier permeability. Among the synthesized hybrids, compound 5s displayed the most balanced inhibitory effect on hAChE (IC50 = 69.8 nM) and hBuChE (IC50 = 68.0 nM), and exhibited promising inhibitory activity against β-secretase-1 (BACE-1) (IC50 = 3.6 µM). Combining inhibition kinetics and molecular model analysis, compound 5s was shown to be a mixed inhibitor affecting both the catalytic active site (CAS) and peripheral anionic site (PAS) of hAChE. Additionally, compound 5s showed low toxicity in PC12 and BV2 cell assays. Moreover, compound 5s demonstrated good tolerance at the dose of up to 2500 mg/kg and exhibited no hepatotoxicity at the dose of 3 mg/kg in mice, and it could effectively improve memory ability in mice. Taken together, these findings suggest that compound 5s is a promising and effective multi-target agent for the potential treatment of AD.

Conjugates of amiridine and thiouracil derivatives as effective inhibitors of butyrylcholinesterase with the potential to block β-amyloid aggregation

New amiridine-thiouracil conjugates with different substituents in the pyrimidine fragment (R = CH3 , CF2 Н, CF3 , (CF2 )2 H) and different spacer lengths (n = 1-3) were synthesized. The conjugates rather weakly inhibit acetylcholinesterase (AChE) and exhibit high inhibitory activity (IC50 up to 0.752 ± 0.021 µM) and selectivity to butyrylcholinesterase (BChE), which increases with spacer elongation; the lead compounds are 11c, 12c, and 13c. The conjugates are mixed-type reversible inhibitors of both cholinesterases and practically do not inhibit the structurally related off-target enzyme carboxylesterase. The results of molecular docking to AChE and BChE are consistent with the experiment on enzyme inhibition and explain the structure-activity relationships, including the rather low anti-AChE activity and the high anti-BChE activity of long-chain conjugates. The lead compounds displace propidium from the AChE peripheral anion site (PAS) at the level of the reference compound donepezil, which agrees with the mixed-type mechanism of AChE inhibition and the main mode of binding of conjugates in the active site of AChE due to the interaction of the pyrimidine moiety with the PAS. This indicates the ability of the studied conjugates to block AChE-induced aggregation of β-amyloid, thereby exerting a disease-modifying effect. According to computer calculations, all synthesized conjugates have an ADME profile acceptable for drugs.

Discovery of novel multifunctional ligands targeting GABA transporters, butyrylcholinesterase, β-secretase, and amyloid β aggregation as potential treatment of Alzheimer's disease

Alzheimer's disease (AD) is a global health problem in the medical sector that will increase over time. The limited treatment of AD leads to the search for a new clinical candidate. Considering the multifactorial nature of AD, a strategy targeting number of regulatory proteins involved in the development of the disease is an effective approach. Here, we present a discovery of new multi-target-directed ligands (MTDLs), purposely designed as GABA transporter (GAT) inhibitors, that successfully provide the inhibitory activity against butyrylcholinesterase (BuChE), β-secretase (BACE1), amyloid β aggregation and calcium channel blockade activity. The selected GAT inhibitors, 19c and 22a - N-benzylamide derivatives of 4-aminobutyric acid, displayed the most prominent multifunctional profile. Compound 19c (mGAT1 IC50 = 10 μM, mGAT4 IC50 = 12 μM and BuChE IC50 = 559 nM) possessed the highest hBACE1 and Aβ40 aggregation inhibitory activity (IC50 = 1.57 μM and 99 % at 10 μM, respectively). Additionally, it showed a decrease in both the elongation and nucleation constants of the amyloid aggregation process. In contrast compound 22a represented the highest activity and a mixed-type of eqBuChE inhibition (IC50 = 173 nM) with hBACE1 (IC50 = 9.42 μM), Aβ aggregation (79 % at 10 μM) and mGATs (mGAT1 IC50 = 30 μM, mGAT4 IC50 = 25 μM) inhibitory activity. Performed molecular docking studies described the mode of interactions with GATs and enzymatic targets. In ADMET in vitro studies both compounds showed acceptable metabolic stability and low neurotoxicity. Successfully, compounds 19c and 22a at the dose of 30 mg/kg possessed statistically significant antiamnesic properties in a mouse model of amnesia caused by scopolamine and assessed in the novel object recognition (NOR) task or the passive avoidance (PA) task.

Exploration of a library of piperonylic acid-derived hydrazones possessing variable aryl functionalities as potent dual cholinesterase and monoamine oxidase inhibitors

A library of piperonylic acid-derived hydrazones possessing variable aryl moiety was synthesized and investigated for their multifunctional properties against cholinesterases (ChEs) and monoamine oxidases (MAOs). The in vitro enzymatic assay results revealed that the tested hydrazones have exhibited excellent cholinesterase inhibition profile. Compound 4i, (E)-N'-(2,3-dichlorobenzylidene)benzo[d][1,3]dioxole-5-carbohydrazide showed promising dual inhibitory profile against AChE (0.048 ± 0.007 μM), BChE (0.89 ± 0.018 μM), and MAO-B (0.95 ± 0.12 μM) enzymes. SAR exploration revealed that the truncation of the linker connecting both the aryl binding sites of the semicarbazone scaffold, by one atom, has relatively suppressed the AChE inhibitory potential. Kinetic studies disclosed that the compound 4i reversibly inhibited AChE enzyme in a competitive manner (Ki = 8.0 ± 0.076 nM), while it displayed a non-competitive and reversible inhibition profile against MAO-B (Ki = 9.6 ± 0.021 µM). Moreover, molecular docking studies of synthesized compounds against ChEs and MAOs provided the crucial molecular features that enable their close association and interaction with the target enzymes. All atomistic simulation studies confirmed the stable association of compound 4i within the active sites of AChE and MAO-B. In addition, theoretical ADMET prediction studies demonstrated the acceptable pharmacokinetic profile of the dual inhibitors. In summary, the attempted lead simplification study afforded a potent dual ChE-MAO-B inhibitor compound that merits further investigation.

Design, synthesis, biological evaluation and molecular docking of cyclic biguanidine compounds as cholinesterase inhibitors

A series of cyclic biguanidine derivatives (E01-E16) was designed, synthesized, characterized by FTIR, NMR, elemental analysis and evaluated as cholinesterase [acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)] inhibitory effects for the treatment of Alzheimer's disease (AD). The cyclic biguanidine derivatives (E01-E16) were obtained as hydrochloride salt from one-pot reaction of 2-cyanoguanidine, p-substitute aniline derivatives and cyclohexanone/4-ethylcyclohexanone in the acidic medium. The crystal structures of compounds E13 and E16 were determined by XRD studies. The in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory assessment of the compounds revealed that compounds showed considerable inhibitory activity. The substitute groups on the phenyl rings have an impact on the inhibitory activity of the compounds. Compound E08, containing an ester group on the phenyl ring, showed the highest inhibitory activity against BuChE (IC50: 97.97 ± 0.13 µM) compared to other compounds. According to the docking result, compound E08 exhibited higher binding affinity (-10.17 kcal/mol) against BuChE than the standard drug tacrine (-7.02 kcal/mol). Compound E08 was orientated towards the active site of the enzyme BuChE.Communicated by Ramaswamy H. Sarma.

Synthesis of indole derivatives as Alzheimer inhibitors and their molecular docking study

Acetylcholinesterase prevails in the healthy brain, with butyrylcholinesterase reflected to play a minor role in regulating brain acetylcholine (ACh) levels. However, BuChE activity gradually increases in patients with (AD), while AChE activity remains unaffected or decays. Both enzymes therefore represent legitimate therapeutic targets for ameliorating the cholinergic deficit considered to be responsible for the declines in cognitive, behavioural, and global functioning characteristic of AD. Current study described the synthesis of indole-based sulfonamide derivatives (1-23) and their biological activity. Synthesis of these scaffolds were achieved by mixing chloro-substituted indole bearing amine group with various substituted benzene sulfonyl chloride in pyridine, under refluxed condition to obtained desired products. All products were then evaluated for AchE and BuchE inhibitory potential compare with positive Donepezil as standard drug for both AchE and BchE having IC50 = 0.016 ± 0.12 and 0.30 ± 0.010 μM respectively. In this regard analog 9 was found potent having IC50 value 0.15 ± 0.050 μM and 0.20 ± 0.10 for both AchE and BuChE respectively. All other derivatives also found with better potential. All compounds were characterized by various techniques such as 1H, 13C-NMR and HREI-MS. In addition, biological activity was maintained to explore the bioactive nature of scaffolds and their protein-ligand interaction (PLI) was checked through molecular docking study.Communicated by Ramaswamy H. Sarma.

An exploration of binding of Hesperidin, Rutin, and Thymoquinone to acetylcholinesterase enzyme using multi-level computational approaches

Alzheimer's disease, an intricate neurological disorder, is impacting an ever-increasing number of individuals globally, particularly among the aging population. For several decades phytochemicals were used as Ayurveda to treat both communicable and non-communicable diseases. Acetylcholinesterase (AChE) is a widely chosen therapeutic target for the development of early prevention and effective management of neurodegenerative diseases. The primary objective of the present study was to investigate the binding potential between Rutin Thymoquinone, Hesperidin and the FDA-approved drug Donepezil with AChE. Additionally, a comparative analysis was conducted. These phytochemicals were docked with the binding site of the AChE experimental complex. The molecular dockings demonstrated that the Hesperidinh showed a better binding affinity of -22.0631 kcal/mol. The ADME/T investigations revealed that the selected phytochemicals are non-toxic and drug-like candidates. Molecular dynamics simulations were implemented to determine the conformational changes of Rutin, hesperidin, Thymoquinone, and Donepezil complexed with AChE. Hesperidin and Donepezil were more stable than Rutin, Thymoquinone complexed with AChE. Next, essential dynamics and defining the secondary structure of protein were to determine the conformational changes in AChE complexed with selected phytochemicals during simulations. Overall, the MD Simulations demonstrated that all complexes in this study achieved stability until 100 ns of the simulation period was performed thrice. The structural analysis of AChE was done using multiple search engines to explore the molecular functions, biological processes, and pathways in which AChE proteins are involved and to identify potential drug targets for various diseases. This present study concludes that Hesperidin was found to be a more potent AChE inhibitors than Rutin, and further experiments are required to determine the effectivity of Hesperidin against neurodegenerative diseases.Communicated by Ramaswamy H. Sarma.

The Antioxidant and Neuroprotective Potential of Leaves and Inflorescences Extracts of Selected Hemp Varieties Obtained with scCO2

Cannabis sativa, a versatile plant with numerous varieties, holds promising potential for a wide range of biological activity. As raw materials for research, we chose leaves and inflorescences of hemp varieties such as Białobrzeskie, Henola, and Tygra, which are cultivated mainly for their fibers or seeds. The choice of extraction is a key step in obtaining the selected compositions of active compounds from plant material. Bearing in mind the lipophilic nature of cannabinoids, we performed supercritical carbon dioxide (scCO2) extraction at 50 °C under 2000 (a) and 6000 PSI (b). The cannabinoid contents were determined with the use of the HPLC-DAD method. The antioxidant capabilities were assessed through a series of procedures, including the DPPH, ABTS, CUPRAC, and FRAP methods. The capacity to inhibit enzymes that play a role in the progression of neurodegenerative diseases, such as acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and tyrosinase was also studied. The dominant cannabinoids in the extracts were cannabidiol (CBD) and cannabidiolic acid (CBDA). The highest concentration of eight cannabinoids was detected in the Tygra inflorescences extract (b). The most notable antioxidant properties were provided by the Tygra inflorescences extract (b). Nonetheless, it was the Henola inflorescences extract (b) that demonstrated the most efficient inhibition of AChE and BChE, and tyrosinase was inhibited the most significantly by the Białobrzeskie inflorescences extract (b). Multidimensional comparative analysis enrolled all assays and revealed that the Henola inflorescences extract (b) showed the most substantial neuroprotective potential.

Design, Synthesis, and Proof of Concept of Balanced Dual Inhibitors of Butyrylcholinesterase (BChE) and Histone Deacetylase 6 (HDAC6) for the Treatment of Alzheimer's Disease

Concomitant inhibition of butyrylcholinesterase (BChE) and histone deacetylase 6 (HDAC6) is supposed to be effective in the treatment of Alzheimer's disease (AD). Inspired by our previous efforts in designing BChE inhibitors, herein, selective BChE and HDAC6 dual inhibitors were successfully identified through the fusion of the core pharmacophoric moiety of BChE and HDAC6 inhibitors. After the structure-activity relationship (SAR) studies, two compounds (24g and 29a) were confirmed to have superior inhibitory activity against BChE (the IC50 against hBChE are 4.0 and 1.8 nM, respectively) and HDAC6 (the IC50 against HDAC6 are 8.9 and 71.0 nM, respectively). These two compounds showed prominently neuroprotective effects in vitro, potent reactive oxygen species (ROS) scavenging effects, and effective metal ion (Fe2+ and Cu2+) chelation. In addition, they exhibited pronounced inhibition of phosphorylated tau and a moderate immunomodulatory effect, with a lack of neurotoxicity at the cellular level. In vivo studies showed that both 24g and 29a ameliorated the cognitive impairment in an Aβ1-42-induced mouse model at a low dosage (2.5 mg/kg). Our data demonstrated that BChE/HDAC6 dual inhibitors could establish the basis for a potential new symptomatic and disease-modifying strategy to treat AD.

The structural modification and biological evaluation of tetrahydrothienopyridine derivatives as selective BChE inhibitors

A series of tetrahydrothienopyridine derivatives have been designed, synthesized, and evaluated as selective BChE inhibitors. Compounds were analyzed via HRMS, 1H NMR, and 13C NMR. The inhibitory effects were evaluated according to the method of Ellman et al. 6n was the most potent and selective inhibitor against BChE (eeAChE IC50 = 686.4 ± 478.6 μM, eqBChE IC50 = 10.5 ± 5.0 nM, SI = 6.5*104, hBChE IC50 = 32.5 ± 6.5 nM). Cell-based assays have confirmed the low neurotoxicity of 6a and 6n and their moderate neuroprotective effects. Compounds 6a and 6n provide novel chemical entities for the treatment of Alzheimer's disease.

Novel drug-like fluorenyl derivatives as selective butyrylcholinesterase and β-amyloid inhibitors for the treatment of Alzheimer's disease

Butyrylcholinesterase (BuChE) and amyloid β (Aβ) aggregation remain important biological target and mechanism in the search for effective treatment of Alzheimer's disease. Simultaneous inhibition thereof by the application of multifunctional agents may lead to improvement in terms of symptoms and causes of the disease. Here, we present the rational design, synthesis, biological evaluation and molecular modelling studies of novel series of fluorene-based BuChE and Aβ inhibitors with drug-like characteristics and advantageous Central Nervous System Multiparameter Optimization scores. Among 17 synthesized and tested compounds, we identified 22 as the most potent eqBuChE inhibitor with IC₅₀ of 38 nM and 37.4% of Aβ aggregation inhibition at 10 μM. Based on molecular modelling studies, including molecular dynamics, we determined the binding mode of the compounds within BuChE and explained the differences in the activity of the two enantiomers of compound 22. A novel series of fluorenyl compounds meeting the drug-likeness criteria seems to be a promising starting point for further development as anti-Alzheimer agents.

Highly selective butyrylcholinesterase inhibitors related to Amaryllidaceae alkaloids - Design, synthesis, and biological evaluation

Butyrylcholinesterase (BChE) is one of the most frequently implicated enzymes in the advanced stage of Alzheimer's disease (AD). As part of our endeavors to develop new drug candidates for AD, we have focused on natural template structures, namely the Amaryllidaceae alkaloids carltonine A and B endowed with high BChE selectivity. Herein, we report the design, synthesis, and in vitro evaluation of 57 novel highly selective human BChE (hBChE) inhibitors. Most synthesized compounds showed hBChE inhibition potency ranging from micromolar to low nanomolar scale. Compounds that revealed BChE inhibition below 100 nM were selected for detailed biological investigation. The CNS-targeted profile of the presented compounds was confirmed theoretically by calculating the BBB score algorithm, these data were corroborated by determining the permeability in vitro using PAMPA-assay for the most active derivatives. The study highlighted compounds 87 (hBChE IC₅₀ = 3.8 ± 0.2 nM) and 88 (hBChE IC₅₀ = 5.7 ± 1.5 nM) as the top-ranked BChE inhibitors. Compounds revealed negligible cytotoxicity for the human neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cell lines compared to BChE inhibitory potential. A crystallographic study was performed to inspect the binding mode of compound 87, revealing essential interactions between 87 and hBChE active site. In addition, multidimensional QSAR analyses were applied to determine the relationship between chemical structures and biological activity in a dataset of designed agents. Compound 87 is a promising lead compound with potential implications for treating the late stages of AD.

Discovery of new, highly potent and selective inhibitors of BuChE - design, synthesis, in vitro and in vivo evaluation and crystallography studies

The symptomatic and disease-modifying effects of butyrylcholinesterase (BuChE) inhibitors provide an encouraging premise for researching effective treatments for Alzheimer's disease. Here, we examined a series of compounds with a new chemical scaffold based on 3-(cyclohexylmethyl)amino-2-hydroxypropyl, and we identified a highly selective hBuChE inhibitor (29). Based on extensive in vitro and in vivo evaluations of the compound and its enantiomers, (R)-29 was identified as a promising candidate for further development. Compound (R)-29 is a potent hBuChE inhibitor (IC₅₀ = 40 nM) with selectivity over AChE and relevant off-targets, including H₁, M₁, α_1A and β₁ receptors. The compound displays high metabolic stability on human liver microsomes (90% of the parent compound after 2 h of incubation), and its safety was confirmed through examining the cytotoxicity on the HepG2 cell line (LC₅₀ = 2.85 μM) and hERG inhibition (less than 50% at 10 μM). While (rac)-29 lacked an effect in vivo and showed limited penetration to the CNS in pharmacokinetics studies, compound (R)-29 exhibited a procognitive effect at 15 mg/kg in the passive avoidance task in scopolamine-treated mice.

Pseudo-irreversible butyrylcholinesterase inhibitors: Structure-activity relationships, computational and crystallographic study of the N-dialkyl O-arylcarbamate warhead

Alongside reversible butyrylcholinesterase inhibitors, a plethora of covalent butyrylcholinesterase inhibitors have been reported in the literature, typically pseudo-irreversible carbamates. For these latter, however, most cases lack full confirmation of their covalent mode of action. Additionally, the available reports regarding the structure-activity relationships of the O-arylcarbamate warhead are incomplete. Therefore, a follow-up on a series of pseudo-irreversible covalent carbamate human butyrylcholinesterase inhibitors and the structure-activity relationships of the N-dialkyl O-arylcarbamate warhead are presented in this study. The covalent mechanism of binding was tested by IC₅₀ time-dependency profiles, and sequentially and increasingly confirmed by kinetic analysis, whole protein LC-MS, and crystallographic analysis. Computational studies provided valuable insights into steric constraints and identified problematic, bulky carbamate warheads that cannot reach and carbamoylate the catalytic Ser198. Quantum mechanical calculations provided further evidence that steric effects appear to be a key factor in determining the covalent binding behaviour of these carbamate cholinesterase inhibitors and their duration of action. Additionally, the introduction of a clickable terminal alkyne moiety into one of the carbamate N-substituents and in situ derivatisation with azide-containing fluorophore enabled fluorescent labelling of plasma human butyrylcholinesterase. This proof-of-concept study highlights the potential of this novel approach and for these compounds to be further developed as clickable molecular probes for investigating tissue localisation and activity of cholinesterases.

In silico and in vitro studies confirm Ondansetron as a novel acetylcholinesterase and butyrylcholinesterase inhibitor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is growing rapidly among the elderly population around the world. Studies show that a lack of acetylcholine and butyrylcholine due to the overexpression of enzymes Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE) may lead to reduced communication between neuron cells. As a result, seeking novel inhibitors targeting these enzymes might be vital for the future treatment of AD. Ondansetron is used to prevent nausea and vomiting caused by chemotherapy or radiation treatments and is herein shown to be a potent inhibitor of cholinesterase. Comparison is made between Ondansetron and FDA-approved cholinesterase inhibitors Rivastigmine and Tacrine. Molecular docking demonstrates that interactions between the studied ligand and aromatic residues in the peripheral region of the active site are important in binding. Molecular dynamics simulations and binding pose metadynamics show that Ondansetron is highly potent against both enzymes and far better than Rivastigmine. Inhibitor activities evaluated by in vitro studies confirm that the drug inhibits AChE and BChE by non-competitive and mixed inhibition, respectively, with IC₅₀ values 33 µM (AChE) and 2.5 µM (BChE). Based on the findings, we propose that Ondansetron may have therapeutic applications in inhibiting cholinesterase, especially for BChE.

Exploiting butyrylcholinesterase inhibitors through a combined 3-D pharmacophore modeling, QSAR, molecular docking, and molecular dynamics investigation†

Alzheimer's disease (AD), a neurodegenerative condition associated with ageing, can occur. AD gradually impairs memory and cognitive function, which leads to abnormal behavior, incapacity, and reliance. By 2050, there will likely be 100 million cases of AD in the world's population. Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition are significant components of AD treatment. This work developed models using the genetic method multiple linear regression, atom-based, field-based, and 3-D pharmacophore modelling. Due to internal and external validation, all of the models have solid statistical (R² > 0.81 and Q² > 0.77) underpinnings. From a pre-plated CNS library (6055), we discovered a hit compound using virtual screening on a QSAR model. Through molecular docking, additional hit compounds were investigated (XP mode). Finally, a molecular dynamics simulation revealed that the Molecule5093-4BDS complex was stable (100 ns). Finally, the expected ADME properties for the hit compounds (Molecule5093, Molecule1076, Molecule4412, Molecule1053, and Molecule3344) were found. According to the results of our investigation and the prospective hit compounds, BuChE inhibitors may be used as a treatment for AD.

Alzheimer's disease (AD), a neurodegenerative condition associated with ageing, can occur.

Potential revival of cholinesterase inhibitors as drugs in veterinary medicine

The cholinergic system is involved in the regulation of all organ systems and has acetylcholine (ACh) as almost its only neurotransmitter. Any substance is called cholinergic if it can alter the action of acetylcholine. Cholinesterases (ChEs) are enzymes that enable the hydrolysis of acetylcholine and in this way ensure homeostasis in cholinergic synapses. Cholinesterase inhibitors (ChEi) are a group of indirect-acting cholinergic agonists that influence the activity of the cholinergic system. Several compounds that can inhibit cholinesterases are of importance to veterinary medicine from pharmacological and toxicological perspective. The frequency of their use in veterinary medicine has fluctuated over the years and is now reduced to a minimum. They are mainly used in agriculture as pesticides, and some are rarely used as parasiticides for companion animals and livestock. In recent years, interest in the use of new cholinesterase inhibitors has increased since canine cognitive dysfunction (CCD) became a recognized and extensively studied disease. Similar to Alzheimer's disease (AD) in humans, CCD can be treated with cholinesterase inhibitors that cross the blood-brain barrier. In this review, the mammalian cholinergic system and the drugs that interact with cholinesterases are introduced. Cholinesterase inhibitors that can be used for the treatment of CCD are described in detail.

Jatamansinol from Nardostachys jatamansi: a multi-targeted neuroprotective agent for Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial progressive and irreversible neurodegenerative disorder characterized by severe memory impairment and cognitive disability in the middle and old-aged human population. There are no proven drugs for AD treatment and prevention. In Ayurveda, medhya plants are used to prepare Rasayana, and its consumption improves memory and cognition. Nardostachys jatamansi (D.Don) DC is a medhya plant used in traditional medicine to treat neurological disorders, and its unique pyranocoumarins can be a potential drug candidate for AD. Given its traditional claims, this study aims to find the multi-target potential efficacy of the ligands (drug molecules) against the AD from N. jatamansi pyranocoumarins using computational drug discovery techniques. Drug likeliness analysis confirms that pyranocoumarins of N. jatamansi, such as seselin, jatamansinol, jatamansine, jatamansinone, and dihydrojatamansin are probable drug candidates for AD. Molecular docking, molecular dynamic simulations, and Molecular Mechanics/Generalized Born Surface Area (MM-GBSA) analysis confirm that dihydrojatamansin inhibits acetylcholinesterase (AChE), and jatamansinol inhibits butyrylcholinesterase (BuChE), glycogen synthase kinase 3β (GSK3β), and kelch-like ECH-associating protein 1 (Keap1) AD therapeutic targets. Therefore, this study provides potential multi-target inhibitors that would further validate experimental studies, leading to new treatments for AD.Communicated by Ramaswamy H. Sarma.

Grid-Type Quaternary Metallosupramolecular Compounds Inhibit Human Cholinesterases through Dynamic Multivalent Interactions

We report the implementation of coordination complexes containing two types of cationic moieties, i. e. pyridinium and ammonium quaternary salt, as potential inhibitors of human cholinesterase enzymes. Utilization of ligands containing NNO-coordination site and binding zinc metal ion allowed mono- and tetra-nuclear complexes to be obtained with corner and grid structural type, respectively, thus affecting the overall charge of the compounds (from +1 to +8). We were able to examine for the first time the multivalency effect of metallosupramolecular species on their inhibitory abilities towards acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Importantly, resolution of the crystal structures of the obtained enzyme-substrate complexes provided a better understanding of the inhibition process at the molecular level.

Synthesis and molecular modeling studies of 1-benzyl-2-indolinones as selective AChE inhibitors

Background: Possible bioisosteres can be developed by replacing the 1-indanone ring (one of three pharmacophore groups) of donepezil with an indoline ring. As H₂S donors, thioamide, thiocarbamate and thiourea groups are also critically important. Materials & methods: The 1-benzyl-2-indolinones 6a-n were designed using molecular modeling and synthesized, and their acetylcholinesterase and butyrylcholinesterase inhibitory effects were then investigated. Results: The compounds 6h (inhibition constant [K_i] = 0.22 μM; selectivity index [SI] = 26.22), 6i (K_i = 0.24 μM; SI = 25.83), 6k (K_i = 0.22 μM; SI = 28.31) and 6n (K_i = 0.21 μM; SI = 27.14) were approximately twofold more effective against and >12-fold more selective for acetylcholinesterase compared with donepezil (K_i = 0.41 μM; SI = 2.12). Analysis of molecular dynamics simulations with compounds 6k and 6n indicated that the preferred binding might be at allosteric binding pocket 4 of the enzyme. Conclusion: Benzyl substitution at the 1-position of the indole ring significantly increased potency and selectivity.

X-ray crystalographic data, absolute configuration, and anticholinesterase effect of dihydromyricitrin 3-O-rhamnoside

Based on our continuous effort to investigate chemistry and biology of the plant secondary metabolites, we were able to isolate a glycosidal flavonoid 1 from the Wild Egyptian Artichoke. The activity of dihydromyricetin 3-O-rhamnoside (sin. dihydromyricitrin, ampelopsin 3-O-rhamnoside) (1) against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE); its absolute configuration using X-ray crystallography were determined for the first time. Inhibitory activity of 1 against AChE and BChE enzymes were determined using a slightly modified version of Ellman's method. Compound 1 was revealed to have a potent inhibition against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC₅₀ values of 0.070 ± 0.008 and 0.071 ± 0.004 mM, respectively, where IC₅₀ values of the reference drug (galanthamine) were 0.023 ± 0.15 and 0.047 ± 0.91 mM. Compound 1 could be a promising molecule against Alzheimer's disease.

Efficient one-pot synthesis of arylated pyrazole-fused pyran analogs: as leads to treating diabetes and Alzheimer's disease

Background: To discover novel lead molecules against diabetes, Alzheimer's disease and oxidative stress, a library of arylated pyrazole-fused pyran derivatives, 1-20, were synthesized in a one-pot reaction. Materials & methods:¹H-NMR spectroscopic and electron ionization mass spectrometry techniques were used to characterize the synthetic hybrid molecules 1-20. Analogs were screened against four indispensable therapeutic targets, including α-amylase, α-glucosidase, acetylcholinesterase and butyrylcholinesterase enzymes. Results: Except for derivatives 17 and 18, all other compounds exhibited varying degrees of inhibitory activities against target enzymes. The kinetic studies revealed that the synthetic molecules followed a competitive-type mode of inhibition for α-amylase and acetylcholinesterase enzymes, as well as a non-competitive mode of inhibition for α-glucosidase and butyrylcholinesterase enzymes. In addition, molecular docking studies identified crucial binding interactions of ligands with the enzyme's active site. Conclusion: These molecules may serve as a potential drug candidate to cure diabetes, Alzheimer's disease and oxidative stress in the future.

Synthesis, In Vitro Anti-Microbial Analysis and Molecular Docking Study of Aliphatic Hydrazide-Based Benzene Sulphonamide Derivatives as Potent Inhibitors of α-Glucosidase and Urease

A unique series of sulphonamide derivatives was attempted to be synthesized in this study using a new and effective method. All of the synthesized compounds were verified using several spectroscopic methods, including FTIR, ¹H-NMR, ¹³C-NMR, and HREI-MS, and their binding interactions were studied using molecular docking. The enzymes urease and α-glucosidase were evaluated against each derivative (1–15). When compared to their respective standard drug such as acarbose and thiourea, almost all compounds were shown to have excellent activity. Among the screened series, analogs 5 (IC₅₀ = 3.20 ± 0.40 and 2.10 ± 0.10 µM) and 6 (IC₅₀ = 2.50 ± 0.40 and 5.30 ± 0.20 µM), emerged as potent molecules when compared to the standard drugs acarbose (IC₅₀ = 8.24 ± 0.08 µM) and urease (IC₅₀ = 7.80 ± 0.30). Moreover, an anti-microbial study also demonstrated that analogs 5 and 6 were found with minimum inhibitory concentrations (MICs) in the presence of standard drugs streptomycin and terinafine.

Resveratrol–Maltol and Resveratrol–Thiophene Hybrids as Cholinesterase Inhibitors and Antioxidants: Synthesis, Biometal Chelating Capability and Crystal Structure

New resveratrol–thiophene and resveratrol–maltol hybrids were synthesized as cholinesterase inhibitors and antioxidants. As with photostability experiments, biological tests also found remarkable differences in the properties and behavior of thiophene and maltol hybrids. While resveratrol–thiophene hybrids have excellent inhibitory and antioxidant properties (similar to the activity of reference drug galantamine), maltols have been proven to be weaker inhibitors and antioxidants. The molecular docking of selected active ligands gave insight into the structures of docked enzymes. It enabled the identification of interactions between the ligand and the active site of both cholinesterases. The maltols that proved to be active cholinesterase inhibitors were able to coordinate Fe³⁺ ion, forming complexes of 1:1 composition. Their formation constants, determined by spectrophotometry, are very similar, lgK = 11.6–12.6, suggesting that Fe³⁺ binds to the common hydroxy-pyranone moiety and is hardly affected by the other aromatic part of the ligand. Accordingly, the characteristic bands in their individual absorption spectra are uniformly red-shifted relative to those of the free ligands. The crystal structures of two new resveratrol–maltol hybrids were recorded, giving additional information on the molecules’ intermolecular hydrogen bonds and packing. In this way, several functionalities of these new resveratrol hybrids were examined as a necessary approach to finding more effective drugs for complicated neurodegenerative diseases.

N-Benzyl Benzamide Derivatives as Selective Sub-Nanomolar Butyrylcholinesterase Inhibitors for Possible Treatment in Advanced Alzheimer's Disease

Herein, we report a series of selective sub-nanomolar inhibitors against butyrylcholinesterase (BChE). These compounds, bearing a novel N-benzyl benzamide scaffold, inhibited BChE with IC₅₀ from picomolar to nanomolar. The inhibitory activity was confirmed by the surface plasmon resonance assay, showing a sub-nanomolar K_D value, which revealed that the compounds exert the inhibitory effect through directly binding to BChE. Several compounds showed neuroprotective effects verified by the oxidative damage model. Furthermore, the safety of S11-1014 and S11-1033 was demonstrated by the in vivo acute toxicity test. In the behavior study, 0.5 mg/kg S11-1014 or S11-1033 exhibited a marked therapeutic effect, which was almost equal to the treatment with 1 mg/kg rivastigmine, against the cognitive impairment induced by Aβ_1-42. The pharmacokinetics studies characterized the metabolic stability of S11-1014. Thus, N-benzyl benzamide inhibitors are promising compounds with drug-like properties for improving cognitive dysfunction, providing a potential strategy for the treatment of Alzheimer's disease.

Triterpenoids as bivalent and dual inhibitors of acetylcholinesterase/butyrylcholinesterase from the fruiting bodies of Inonotus obliquus

Inonotus obliquus, an edible and medicinal mushroom parasitic on birches, has been used in human diet and for traditional therapies in the high latitude regions of Europe and Asia for a long time. Our phytochemical study of this fungus led to the identification of fourteen triterpenoids including four undescribed ones, and two pairs of undescribed phenolic enantiomers. The undescribed compounds were elucidated by extensive spectroscopic analysis including 1D and 2D NMR and HRESIMS, quantum chemical NMR and ECD calculations, as well as single-crystal X-ray diffraction analysis. Bioassays revealed that eight compounds showed dual inhibition against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) with IC₅₀ values ranging from 2.40 ± 0.05 to 28.72 ± 0.46 μM, while 3β-hydroxy-lanosra-8,24-dien-21-al and trametenolic acid only presented BuChE inhibitory activities with IC₅₀ values of 22.21 ± 1.01 and 7.68 ± 0.13 μM, respectively. In the kinetic studies, the most active three compounds acted as non-competitive inhibitors for both cholinesterases. Furthermore, molecular docking simulations revealed that three compounds demonstrated dual-sites bounding to AChE/BuChE. These triterpenoids emerged as bivalent and dual inhibitors of AChE/BuChE and could be effective drug candidates to prevent and treat Alzheimer's disease in the future.

Discovery of carbamate-based N-salicyloyl tryptamine derivatives as novel pleiotropic agents for the treatment of Alzheimer's disease

In this work, based on the potential anti-AD molecule previously studied by our group, we continue to introduce different substituents at different positions to improve both drug-like properties and on target activities. 33 N-salicyloyl tryptamine-carbamate hybrids were designed, synthesized and evaluated as cholinesterase inhibitors. H327 was the most potent BChE inhibitor (eqBChE IC₅₀ = 0.057 ± 0.005 μM), and showed threefold improved inhibitory potency than the positive drug rivastigmine (eqBChE IC₅₀ = 0.19 ± 0.001 μM). In addition, H327 as a pseudo-irreversible BChE inhibitor was endowed with neuroprotective, antioxidative and anti-neuroinflammatory properties. Cytotoxicity and acute toxicity tests confirmed the safety of compound H327. The pharmacokinetics study showed that compound H327 had a longer T_1/2 time and higher bioavailability than the lead compound 1 g. Compound H327 was able to cross the blood-brain barrier (BBB) in vivo. Moreover, the behavioral tests showed that compound H327 could significantly improve scopolamine-induced cognitive impairment in vivo. Overall, these results demonstrated that compound H327 is a promising multi-target agent for the treatment of AD.

Conformational Properties of New Thiosemicarbazone and Thiocarbohydrazone Derivatives and Their Possible Targets

The structure assignment and conformational analysis of thiosemicarbazone KKI15 and thiocarbohydrazone KKI18 were performed through homonuclear and heteronuclear 2D Nuclear Magnetic Resonance (NMR) spectroscopy (2D-COSY, 2D-NOESY, 2D-HSQC, and 2D-HMBC) and quantum mechanics (QM) calculations using Functional Density Theory (DFT). After the structure identification of the compounds, various conformations of the two compounds were calculated using DFT. The two molecules showed the most energy-favorable values when their two double bonds adopted the E configuration. These configurations were compatible with the spatial correlations observed in the 2D-NOESY spectrum. In addition, due to the various isomers that occurred, the energy of the transition states from one isomer to another was calculated. Finally, molecular binding experiments were performed to detect potential targets for KKI15 and KKI18 derived from SwissAdme. In silico molecular binding experiments showed favorable binding energy values for all four enzymes studied. The strongest binding energy was observed in the enzyme butyrylcholinesterase. ADMET calculations using the preADMET and pKCSm software showed that the two molecules appear as possible drug leads.

Photoswitchable Pseudoirreversible Butyrylcholinesterase Inhibitors Allow Optical Control of Inhibition in Vitro and Enable Restoration of Cognition in an Alzheimer's Disease Mouse Model upon Irradiation

To develop tools to investigate the biological functions of butyrylcholinesterase (BChE) and the mechanisms by which BChE affects Alzheimer's disease (AD), we synthesized several selective, nanomolar active, pseudoirreversible photoswitchable BChE inhibitors. The compounds were able to specifically influence different kinetic parameters of the inhibition process by light. For one compound, a 10-fold difference in the IC₅₀-values (44.6 nM cis, 424 nM trans) in vitro was translated to an "all or nothing" response with complete recovery in a murine cognition-deficit AD model at dosages as low as 0.3 mg/kg.

Dimethoxyindoles based thiosemicarbazones as multi-target agents; synthesis, crystal interactions, biological activity and molecular modeling

Alzheimer's disease (AD) is known as one of the most devastating neurodegenerative disease diagnosed for the old-aged people and cholinesterase inhibitors (ChEI) can be used as an effective palliative treatment for AD. A range of novel monomeric and dimeric indole based thiosemicarbazone derivatives 17-28 was synthesized in order to target cholinesterases (ChE). Biological importance of the targeted compounds 17-28 was investigated by employing the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes along with three different antioxidant property determination assays, namely DPPH free radical scavenging, ABTS cationic radical decolarization, and CUPRAC cupric reducing antioxidant capacity. The compounds 18 and 19 displayed the best inhibitor activity against BChE with IC₅₀ values of 7.42 and 1.95 μM, respectively. The antioxidant potentials were found to be moderate for DPPH and ABTS assays and the compounds 28 and 18 were the most potent candidates for both antioxidant assays. Cupric reducing capacity was the most promising assay and the compounds 25, 26 and 28 provided better inhibition values than all the standards. Further binding mode and affinity studies performed by molecular docking and molecular dynamics simulations. Accordingly, the compound 19 is the most plausible candidate that can compete with galantamine (GNT), a common pharmaceutics targeting both cholinesterase enzymes.

Spatial Distribution and Stability of Cholinesterase Inhibitory Protoberberine Alkaloids from Papaver setiferum

During a research program to identify new cholinesterase inhibitors of natural origin, two new 7,8-didehydroprotoberberine alkaloids (1 and 2) and nine known compounds (3-11) were isolated from the capsules of the common ornamental poppy, Papaver setiferum (previously P. pseudo-orientale). Despite their reported instability, the 7,8-didehydroprotoberberines isolated herein appeared relatively stable, particularly as their trifluoroacetic acid salts. The spatial distributions of the isolated alkaloids were also analyzed using desorption electrospray ionization imaging mass spectrometry. The alkaloids were localized predominantly within the walls and vascular bundles of the capsules, with the highest relative abundances occurring in the lower half of the capsules toward the peduncle. The relative abundances of the alkaloids were also compared across plant development stages. Although most alkaloids did not show clear patterns in their concentration across development stages, the concentration of suspected oxidation products clearly spiked upon plant death. Finally, all isolated natural products were screened for inhibitory activities against a panel of cholinesterases, from both human and animal sources. These studies identified several competitive inhibitors of cholinesterases with potency in the low micromolar range (1-4, 6, 7), offering new lead compounds for the development of cholinesterase inhibitory drugs.

Development and crystallography-aided SAR studies of multifunctional BuChE inhibitors and 5-HT6R antagonists with β-amyloid anti-aggregation properties

The lack of an effective treatment makes Alzheimer's disease a serious healthcare problem and a challenge for medicinal chemists. Herein we report interdisciplinary research on novel multifunctional ligands targeting proteins and processes involved in the development of the disease: BuChE, 5-HT₆ receptors and β-amyloid aggregation. Structure-activity relationship analyses supported by crystallography and docking studies led to the identification of a fused-type multifunctional ligand 50, with remarkable and balanced potencies against BuChE (IC₅₀ = 90 nM) and 5-HT₆R (K_i = 4.8 nM), and inhibitory activity against Aβ aggregation (53% at 10 μM). In in vitro ADME-Tox and in vivo pharmacokinetic studies compound 50 showed good stability in the mouse liver microsomes, favourable safety profile and brain permeability with the brain to plasma ratio of 6.79 after p.o. administration in mice, thus being a promising candidate for in vivo pharmacology studies and a solid foundation for further research on effective anti-AD therapies.

Discovery of 1-(phenylsulfonyl)-1H-indole-based multifunctional ligands targeting cholinesterases and 5-HT6 receptor with anti-aggregation properties against amyloid-beta and tau

Multifunctional ligands as an essential variant of polypharmacology are promising candidates for the treatment of multi-factorial diseases like Alzheimer's disease. Based on clinical evidence and following the paradigm of multifunctional ligands we have rationally designed and synthesized a series of compounds targeting processes involved in the development of the disease. The biological evaluation led to the discovery of two compounds with favorable pharmacological characteristics and ADMET profile. Compounds 17 and 35 are 5-HT₆R antagonists (K_i = 13 nM and K_i = 15 nM respectively) and cholinesterase inhibitors with distinct mechanisms of enzyme inhibition. Compound 17, a tacrine derivative is a reversible inhibitor of acetyl- and butyrylcholinesterase (IC₅₀ = 8 nM and IC₅₀ = 24 nM respectively), while compound 35 with rivastigmine-derived phenyl N-ethyl-N-methylcarbamate fragment is a selective, pseudo-irreversible inhibitor of butyrylcholinesterase (IC₅₀ = 455 nM). Both compounds inhibit aggregation of amyloid β in vitro (75% for compound 17 and 68% for 35 at 10 μM) moreover, compound 35 is a potent tau aggregation inhibitor in cellulo (79%). In ADMET in vitro studies both compounds showed acceptable metabolic stability on mouse liver microsomes (28% and 60% for compound 17 and 35 respectively), no or little effect on CYP3A4 and 2D6 up to a concentration of 10 μM and lack of toxicity on HepG2 cell line (IC₅₀ values of 80 and 21 μM, for 17 and 35 respectively). Based on the pharmacological characteristics and favorable pharmacokinetic properties, we propose compounds 17 and 35 as an excellent starting point for further optimization and in-depth biological studies.

Identification of Compounds for Butyrylcholinesterase Inhibition

Butyrylcholinesterase (BChE) is a nonspecific cholinesterase enzyme that hydrolyzes choline-based esters. BChE plays a critical role in maintaining normal cholinergic function like acetylcholinesterase (AChE) through hydrolyzing acetylcholine (ACh). Selective BChE inhibition has been regarded as a viable therapeutic approach in Alzheimer's disease. As of now, a limited number of selective BChE inhibitors are available. To identify BChE inhibitors rapidly and efficiently, we have screened 8998 compounds from several annotated libraries against an enzyme-based BChE inhibition assay in a quantitative high-throughput screening (qHTS) format. From the primary screening, we identified a group of 125 compounds that were further confirmed to inhibit BChE activity, including previously reported BChE inhibitors (e.g., bambuterol and rivastigmine) and potential novel BChE inhibitors (e.g., pancuronium bromide and NNC 756), representing diverse structural classes. These BChE inhibitors were also tested for their selectivity by comparing their IC50 values in BChE and AChE inhibition assays. The binding modes of these compounds were further studied using molecular docking analyses to identify the differences between the interactions of these BChE inhibitors within the active sites of AChE and BChE. Our qHTS approach allowed us to establish a robust and reliable process to screen large compound collections for potential BChE inhibitors.

Novel chrysin derivatives as hidden multifunctional agents for anti-Alzheimer's disease: design, synthesis and in vitro evaluation

Alzheimer's disease (AD) is the most common type of dementia, the exact etiology of the disease has not been known yet. The use of single-target drugs limits the efficacy of drugs and has certain side effects. In this study, the 'hidden' multi-target strategy was used in combination with chrysin's metal chelating site and rivastigmine's anti-cholinesterase pharmacophore to form an ester, which improves the hydrophobicity and protects the phenolic hydroxyl group at the same time. Four derivatives (1-4) were synthesized as the hidden multifunctional agents for AD therapy. Most of the compounds displayed good activities of anti-cholinesterase, antioxidant, appropriate blood brain barrier (BBB) penetration and certain inhibitory activity of β-amyloid (Aβ) aggregation. Compound 3 was demonstrated as the highest selective butyrylcholinesterase (BuChE) inhibitor and targeted both the catalytic active site (CAS) and the peripheral anion site (PAS). And it could be hydrolyzed by BuChE to release chrysin with good ability to chelate Cu²⁺ and Fe²⁺. At the same time, phenol fragment can exert its good antioxidant effect. Overall, these findings demonstrated that compound 3 might be considered as a potential hidden multifunctional candidate in the therapy of AD.

Treatment of canine cognitive dysfunction with novel butyrylcholinesterase inhibitor

Canine cognitive dysfunction (CCD) is common in aged dogs and has many similarities with Alzheimer’s disease. Unfortunately, like Alzheimer’s disease, CCD cannot be cured. In the present study, we treated dogs with CCD with our newly developed and characterized butyrylcholinesterase inhibitor (BChEi). Seventeen dogs were randomized into two groups (treated with BChEi and untreated) and followed for 6 months at regular check-ups. The dogs’ cognitive status was determined by a Canine Dementia Scale (CADES) questionnaire and two cognitive tests. In dogs with moderate cognitive impairment, treatment caused significant improvement in the clinical rating of cognitive abilities and the performance-based tests of cognitive functioning when compared to the untreated group (p < 0.001). Dogs treated with BChEi showed markedly improved cognitive function with enhanced quality of life. No side effects were observed in the treated dogs with moderate cognitive impairment. According to the results of this preliminary study, there is an indication that novel BChEi may be a promising drug for the treatment of CCD in dogs and may be an interesting candidate for the treatment of Alzheimer's disease in humans. However, further clinical studies are needed to confirm this.

Conjugation of Aminoadamantane and γ-Carboline Pharmacophores Gives Rise to Unexpected Properties of Multifunctional Ligands

A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer’s disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure–activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action.

Neuroprotective derivatives of tacrine that target NMDA receptor and acetyl cholinesterase - Design, synthesis and biological evaluation

The complex and multifactorial nature of neuropsychiatric diseases demands multi-target drugs that can intervene with various sub-pathologies underlying disease progression. Targeting the impairments in cholinergic and glutamatergic neurotransmissions with small molecules has been suggested as one of the potential disease-modifying approaches for Alzheimer’s disease (AD). Tacrine, a potent inhibitor of acetylcholinesterase (AChE) is the first FDA approved drug for the treatment of AD. Tacrine is also a low affinity antagonist of N-methyl-D-aspartate receptor (NMDAR). However, tacrine was withdrawn from its clinical use later due to its hepatotoxicity. With an aim to develop novel high affinity multi-target directed ligands (MTDLs) against AChE and NMDAR, with reduced hepatotoxicity, we performed in silico structure-based modifications on tacrine, chemical synthesis of the derivatives and in vitro validation of their activities. Nineteen such derivatives showed inhibition with IC₅₀ values in the range of 18.53 ± 2.09 – 184.09 ± 19.23 nM against AChE and 0.27 ± 0.05 – 38.84 ± 9.64 μM against NMDAR. Some of the selected compounds also protected rat primary cortical neurons from glutamate induced excitotoxicity. Two of the tacrine derived MTDLs, 201 and 208 exhibited in vivo efficacy in rats by protecting against behavioral impairment induced by administration of the excitotoxic agent, monosodium glutamate. Additionally, several of these synthesized compounds also exhibited promising inhibitory activitiy against butyrylcholinesterase. MTDL-201 was also devoid of hepatotoxicity in vivo. Given the therapeutic potential of MTDLs in disease-modifying therapy, our studies revealed several promising MTDLs among which 201 appears to be a potential candidate for immediate preclinical evaluations.

Novel Sulfonamide-Based Carbamates as Selective Inhibitors of BChE

A series of 14 target benzyl [2-(arylsulfamoyl)-1-substituted-ethyl]carbamates was prepared by multi-step synthesis and characterized. All the final compounds were tested for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro, and the selectivity index (SI) was determined. Except for three compounds, all compounds showed strong preferential inhibition of BChE, and nine compounds were even more active than the clinically used rivastigmine. Benzyl {(2S)-1-[(2-methoxybenzyl)sulfamoyl]-4-methylpentan-2-yl}carbamate (5k), benzyl {(2S)-1-[(4-chlorobenzyl)sulfamoyl]-4-methylpentan-2-yl}carbamate (5j), and benzyl [(2S)-1-(benzylsulfamoyl)-4-methylpentan-2-yl]carbamate (5c) showed the highest BChE inhibition (IC50 = 4.33, 6.57, and 8.52 µM, respectively), indicating that derivatives 5c and 5j had approximately 5-fold higher inhibitory activity against BChE than rivastigmine, and 5k was even 9-fold more effective than rivastigmine. In addition, the selectivity index of 5c and 5j was approx. 10 and that of 5k was even 34. The process of carbamylation and reactivation of BChE was studied for the most active derivatives 5k, 5j. The detailed information about the mode of binding of these compounds to the active site of both BChE and AChE was obtained in a molecular modeling study. In this study, combined techniques (docking, molecular dynamic simulations, and QTAIM (quantum theory of atoms in molecules) calculations) were employed.