A cascade synthesis, in vitro cholinesterases inhibitory activity and docking studies of novel Tacrine-pyranopyrazole derivatives

In this work, we describe the preparation of some new Tacrine analogues modified with a pyranopyrazole moiety. A one-pot multicomponent reaction of 3-methyl-1H-pyrazol-5(4H)-one, aryl(or hetero)aldehydes, malononitrile and cyclohexanone involving a Friedländer condensation led to the title compounds. The synthesized heterocyclic analogues of this molecule were evaluated in vitro for their AChE and BChE inhibitory activities in search for potent cholinesterase enzyme inhibitors. Most of the synthesized compounds displayed remarkable AChE inhibitory activities with IC₅₀ values ranging from 0.044 to 5.80?µM, wherein compounds 5e and 5j were found to be most active inhibitors against AChE with IC₅₀ values of 0.058 and 0.044?µM respectively. Molecular modeling simulation on AChE and BChE receptors, showed good correlation between IC₅₀ values and binding interaction template of the most active inhibitors docked into the active site of their relevant enzymes.     

Novel N-benzylpyridinium moiety linked to arylisoxazole derivatives as selective butyrylcholinesterase inhibitors: Synthesis,biological evaluation,and docking study

A novel series of N-benzylpyridinium moiety linked to arylisoxazole ring were designed, synthesized, and evaluated for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Synthesized compounds were classified into two series of 5a-i and 5j-q considering the position of positively charged nitrogen of pyridinium moiety (3- or 4- position, respectively) connected to isoxazole carboxamide group. Among the synthesized compounds, compound 5n from the second series of compounds possessing 2,4-dichloroaryl group connected to isoxazole ring was found to be the most potent AChE inhibitor (IC₅₀ = 5.96 µM) and compound 5j also from the same series of compounds containing phenyl group connected to isoxazole ring demonstrated the most promising inhibitory activity against BChE (IC₅₀ = 0.32 µM). Also, kinetic study demonstrated competitive inhibition mode for both AChE and BChE inhibitory activity. Docking study was also performed for those compounds and desired interactions with those active site amino acid residues were confirmed through hydrogen bonding as well as π-π and π-anion interactions. In addition, the most potent compounds were tested against BACE1 and their neuroprotectivity on Aβ-treated neurotoxicity in PC12 cells which depicted negligible activity. It should be noted that most of the synthesized compounds from both categories 5a-i and 5j-q showed a significant selectivity toward BChE. However, series 5j-q were more active toward AChE than series 5a-i.     

Triazole substituted metal-free,metallo-phthalocyanines and their water soluble derivatives as potential cholinesterases inhibitors: Design,synthesis and in vitro inhibition study

In this study, 1,2,3-triazole substituted metal-free and metallo phthalocyanines (4, 5, 6) and their water soluble derivatives (4a, 5a, 6a) were designed, synthesized for the first time and tested in vitro on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. Most phthalocyanines exhibited good inhibitory activities on these enzymes. Among the six phthalocyanines and starting compounds, 4a showed the most interesting profile as a submicromolar selective inhibitor of AChE (IC₅₀ = 0.040 µM) and 5a showed the most effective inhibitor of BChE (IC₅₀ = 0.1198 µM).     

Synthesis and cholinesterase inhibitory activity study of new piperidone grafted spiropyrrolidines

Alzheimer’s disease (AD) is a prevalent neurodegenerative disorder, which affected 35 million people in the world. The most practiced approach to improve the life expectancy of AD patients is to increase acetylcholine neurotransmitter level at cholinergic synapses by inhibition of cholinesterase enzymes. A series of unreported piperidone grafted spiropyrrolidines 8(a-p) were synthesized and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Therein, compounds 8h and 8l displayed more potent AChE enzyme inhibition than standard drug with IC₅₀ values of 1.88 and 1.37 µM, respectively. Molecular docking simulations for 8l possessing the most potent AChE inhibitory activities, disclosed its interesting binding templates to the active site channel of AChE enzymes. These compounds are remarkable AChE inhibitors and have potential as AD drugs.     

Synthesis and biological evaluation of new pyrazolone Schiff bases as monoamine oxidase and cholinesterase inhibitors

In the current work, Schiff base derivatives of antipyrine were synthesized. The chemical characterization of the compounds was confirmed using IR, ¹H NMR, ¹³C NMR and mass spectroscopies. The inhibitory potency of synthesized compounds was investigated towards acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and monoamine oxidases A and B (MAO-A and MAO-B) enzymes. Some of the compounds displayed significant inhibitory activity against AChE and MAO-B enzymes, respectively. According to AChE enzyme inhibition assay, compounds 3e and 3g were found as the most potent derivatives with IC₅₀ values of 0.285 µM and 0.057 µM, respectively. Also, compounds 3a (IC₅₀ = 0.114 µM), 3h (IC₅₀ = 0.049 µM), and 3i (IC₅₀ = 0.054 µM) were the most active derivatives against MAO-B enzyme activity. So as to understand inhibition type, enzyme kinetics studies were carried out. Furthermore, molecular docking studies were performed to define and evaluate the interaction mechanism between compounds 3g and 3h and related enzymes. ADME (Absorption, Distribution, Metabolism, and Excretion) and BBB (Blood, Brain, Barier) permeability predictions were applied to estimate pharmacokinetic profiles of synthesized compounds.     

Combined molecular modeling and cholinesterase inhibition studies on some natural and semisynthetic O-alkylcoumarin derivatives

Coumarins of synthetic or natural origins are an important chemical class exerting diverse pharmacological activities. In the present study, 26 novel O-alkylcoumarin derivatives were synthesized and have been tested at 100 µM for their in vitro inhibitory potential against acetylcholinesterase (AChE) and butyrlcholinesterase (BChE) targets which are the key enzymes playing role in the pathogenesis of Alzheimer’s disease. Among the tested coumarins, none of them could inhibit AChE, whereas 12 of them exerted a marked and selective inhibition against BChE as compared to the reference (galanthamine, IC₅₀ = 46.58 ± 0.91 µM). In fact, 10 of the active coumarins showed higher inhibition (IC₅₀ = 7.01 ± 0.28 µM – 43.31 ± 3.63 µM) than that of galanthamine. The most active ones were revealed to be 7-styryloxycoumarin (IC₅₀ = 7.01 ± 0.28 µM) and 7-isopentenyloxy-4-methylcoumarin (IC₅₀ = 8.18 ± 0.74 µM). In addition to the in vitro tests, MetaCore/MetaDrug binary QSAR models and docking simulations were applied to evaluate the active compounds by ligand-based and target-driven approaches. The predicted pharmacokinetic profiles of the compounds suggested that the compounds reveal lipophilic character and permeate blood brain barrier (BBB) and the ADME models predict higher human serum protein binding percentages (>50%) for the compounds. The calculated docking scores indicated that the coumarins showing remarkable BChE inhibition possessed favorable free binding energies in interacting with the ligand-binding domain of the target. Therefore, our results disclose that O-alkylcoumarins are promising selective inhibitors of cholinesterase enzymes, particularly BChE in our case, which definitely deserve further studies.     

Synthesis and discovery of highly functionalized mono- and bis-spiro-pyrrolidines as potent cholinesterase enzyme inhibitors

Novel mono and bis spiropyrrolidine derivatives were synthesized via an efficient ionic liquid mediated, 1,3-dipolar cycloaddition methodology and evaluated in vitro for their AChE and BChE inhibitory activities in search for potent cholinesterase enzyme inhibitors. Most of the synthesized compounds displayed remarkable AChE inhibitory activities with IC₅₀ values ranging from 1.68 to 21.85 μM, wherein compounds 8d and 8j were found to be most active inhibitors against AChE and BChE with IC₅₀ values of 1.68 and 2.75 μM, respectively. Molecular modeling simulation on Torpedo californica AChE and human BChE receptors, showed good correlation between IC₅₀ values and binding interaction template of the most active inhibitors docked into the active site of their relevant enzymes.     

Highly selective carbamate-based butyrylcholinesterase inhibitors derived from a naturally occurring pyranoisoflavone

This current study described the design and synthesis of a series of derivatives based on a natural pyranoisaflavone, which was obtained from the seeds of Millettia pachycarpa and displayed attractive BChE inhibition and high selectivity in our previous study. The inhibitory potential of all derivatives against two cholinesterases was evaluated. Only a few compounds demonstrated AChE inhibitory activity at the tested concentrations, while 26 compounds showed significant inhibition on BChE (the IC₅₀ values varied from 9.34 μM to 0.093 μM), most of them presented promising selectivity to ward BChE. Prediction of ADME properties for 7 most active compounds was performed. Among them, 9g (IC₅₀ = 222 nM) and 9h (IC₅₀ = 93 nM) were found to be the most potent BChE inhibitors with excellent selectivity over AChE (SI ratio = 1339 and 836, respectively). The kinetic analysis demonstrated both of them acted as mixed-type BChE inhibitors, while the molecular docking results indicated that they interacted with both residues in the catalytic active site. A cytotoxicity test on PC12 cells showed that both 9g and 9h had a therapeutic safety range similar to tacrine. Overall, the results indicate that 9h could be a good candidate of BChE inhibitors.     

Design,Synthesis, and Biological Evaluation of Novel Indanone Derivatives as Cholinesterase Inhibitors for Potential Use in Alzheimer's Disease

Indanone derivatives containing meta/para-substituted aminopropoxy benzyl/benzylidene moieties were designed based on the structures of donepezil and ebselen analogs as the cholinesterase inhibitors. The designed compounds were synthesized and their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were measured. Inhibitory potencies (IC₅₀ values) for the synthesized compounds ranged from 0.12 to 11.92 μM and 0.04 to 24.36 μM against AChE and BChE, respectively. Compound 5 c showed the highest AChE inhibitory potency with IC₅₀ value of 0.12 μM, whereas the highest BChE inhibition was achieved by structure 7 b (IC₅₀=0.04 μM). Structure-activity relationship (SAR) analysis revealed that there is no significant difference between meta and para-substituted derivatives in AChE and BChE inhibition. However, the most potent AChE inhibitor 5 c belongs to meta-substituted compounds, while the most active BChE inhibitor is para-substituted derivative 7 b . The order of enzyme inhibition potency based on the substituted amine group is dimethyl amine>piperidine>morpholine. Compounds containing C=C linkage are more potent AChE inhibitors than the corresponding saturated structures. Molecular docking studies indicated that 5 c interacts with AChE in a very similar way to that observed experimentally for donepezil. The introduced indanone-aminopropoxy benzylidenes could be used in drug-discovery against Alzheimer's disease.     

Synthesis and 2D-QSAR study of dispiropyrrolodinyl-oxindole based alkaloids as cholinesterase inhibitors

In this work, we describe the regioselective synthesis of some new dispiro[indene-2,3′-pyrrolidine-2′,3″-indoline]-1,2″(3H)-dione 4-29 attributable to the previously described methods. All the new chemical entities were assessed in-vitro as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes; while no significant inhibitory activity for the tested compounds were assigned on AChE, compounds 4, 27, 29, 28 and 15 were the most active against BChE enzyme with IC₅₀ = 13.7 µM, 21.8 µM, 22.1 µM, 22.9 µM and 24.9 µM respectively compared to Donepezil (IC₅₀ = 0.72 µM). Compound 4 was found to have a mixed type mode of inhibition, the bioactivity of the new chemical entities (N = 26, n = 5, R² = 0.893, R² cvOO = 0.831, R² cvMO = 0.838, F = 33.32, s² = 0.003) was elucidated via a statistically significant QSAR model utilizing CODESSA-Pro software that validated the observed results.     

Design,synthesis and cholinesterase inhibitory properties of new oxazole benzylamine derivatives

Abstract

The enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are primary targets in attenuating the symptoms of neurodegenerative diseases. Their inhibition results in elevated concentrations of the neurotransmitter acetylcholine which supports communication among nerve cells. It was previously shown for trans-4/5-arylethenyloxazole compounds to have moderate AChE and BChE inhibitory properties. A preliminary docking study showed that elongating oxazole molecules and adding a new NH group could make them more prone to bind to the active site of both enzymes. Therefore, new trans-amino-4-/5-arylethenyl-oxazoles were designed and synthesised by the Buchwald-Hartwig amination of a previously synthesised trans-chloro-arylethenyloxazole derivative. Additionally, naphthoxazole benzylamine photoproducts were obtained by efficient photochemical electrocyclization reaction. Novel compounds were tested as inhibitors of both AChE and BChE. All of the compounds exhibited binding preference for BChE over AChE, especially for trans-amino-4-/5-arylethenyl-oxazole derivatives which inhibited BChE potently (IC₅₀ in µM range) and AChE poorly (IC₅₀?100?µM). Therefore, due to the selectivity of all of the tested compounds for binding to BChE, these compounds could be applied for further development of cholinesterase selective inhibitors.

• HIGHLIGHTS

• Series of oxazole benzylamines were designed and synthesised

• The tested compounds showed binding selectivity for BChE

• Naphthoxazoles were more potent AChE inhibitors

     

Investigation of salicylanilide and 4-chlorophenol-based N-monosubstituted carbamates as potential inhibitors of acetyl- and butyrylcholinesterase

Based on the presence of carbamate moiety, twenty salicylanilide N-monosubstituted carbamates concomitantly with their parent salicylanilides and five newly prepared 4-chlorophenyl carbamates obtained from isocyanates were investigated using Ellman’s method for their in vitro inhibitory activity against acetylcholinesterase (AChE) from electric eel and butyrylcholinesterase (BChE) from equine serum. The carbamates and salicylanilides exhibited mostly a moderate inhibition of both cholinesterase enzymes with IC₅₀ values ranging from 5 to 235 µM. IC₅₀ values for AChE were in a narrower concentration range when compared to BChE, but many of the compounds produced a balanced inhibition of both cholinesterases. The derivatives were comparable or superior to rivastigmine for AChE inhibition, but only a few of carbamates also for BChE. Several structure-activity relationships were identified, e.g., N-phenethylcarbamates produce clearly favourable BChE inhibition. The compounds also share convenient physicochemical properties for CNS penetration.     

Alkynyl and β-ketophosphonates: Selective and potent butyrylcholinesterase inhibitors

A series of thirty-three alkynyl and β-ketophosphonates were evaluated for their in vitro acetyl- and butyryl-cholinesterase (AChE and BChE) inhibitory activities using Ellman’s spectrophotometric method. None of the examined compounds inhibited AChE activity at tested concentrations while twenty-nine of them showed significant and selective inhibition of BChE with IC₅₀ values between 38.60 µM and 0.04 µM. In addition, structure-activity relationships were discussed. The most effective inhibitors were the dibutyl o-methoxyphenyl alkynylphosphonate 3dc and dibutyl o-methoxyphenyl β-ketophosphonate 4dc. Activities of most potent compounds were also compared with a commercial organophosphorus compound. These results could inspire the design of new inhibitors with stronger activity against BChE.     

Cholinesterase inhibitory activity versus aromatic core multiplicity: A facile green synthesis and molecular docking study of novel piperidone embedded thiazolopyrimidines

Novel thiazolopyrimidine derivatives have been synthesized via microwave assisted, domino cascade methodology in ionic liquid and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Among the newly synthesized compounds 6d, 6a, 6e and 6b displayed higher AChE inhibitory activity than standard drug, galanthamine, with IC₅₀ values of 0.53, 1.47, 1.62 and 2.05 μM, respectively. Interestingly, all the compounds except for 6m–r and 6x displayed higher BChE inhibitory potentials than galanthamine with IC₅₀ values ranging from 1.09 to 18.56 μM. Molecular docking simulations for 6d possessing the most potent AChE and BChE inhibitory activities, disclosed its binding interactions at the active site gorge of AChE and BChE enzymes.     

Design,synthesis and evaluation of new thiazole-piperazines as acetylcholinesterase inhibitors

In this study, some new 2-(4-substituted piperazine-1-yl)-N-[4-(2-methylthiazol-4-yl)phenyl]acetamide derivatives were synthesized. The synthesized compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes by in vitro Ellman’s method. The structural elucidation of the compounds was performed by using IR, ¹H-NMR, ¹³C-NMR and FAB⁺-MS spectral data and elemental analyses results. Biological assays revealed that at 0.1 µM concentration, the most active compounds against AChE were 5n, 5o and 5p that indicated 96.44, 99.83 and 89.70% inhibition rates, respectively. Besides, IC₅₀ value of the compound 5o was determined as 0.011 µM, whereas IC₅₀ value of standard drug donepezil was 0.054 µM. The synthesized compounds did not show any notable inhibitory activity against BChE.     

Design,synthesis and biological evaluation of benzofuran appended benzothiazepine derivatives as inhibitors of butyrylcholinesterase and antimicrobial agents

A series of bezofuran appended 1,5-benzothiazepine compounds 7a–v was designed, synthesized and evaluated as cholinesterase inhibitors. The biological assay experiments showed that most of the compounds displayed a clearly selective inhibition for butyrylcholinesterase (BChE), while a weak or no effect towards acetylcholinesterase (AChE) was detected. All analogs exhibited varied BChE inhibitory activity with IC₅₀ value ranging between 1.0?±?0.01 and 72?±?2.8?μM when compared with the standard donepezil (IC₅₀, 2.63?±?0.28?μM). Among the synthesized derivatives, compounds 7l, 7m and 7k exhibited the highest BChE inhibition with IC₅₀ values of 1.0, 1.0 and 1.8?μM, respectively. The results from a Lineweaver-Burk plot indicated a mixed-type inhibition for compound 7l with BChE. In addition, docking studies confirmed the results obtained through in vitro experiments and showed that most potent compounds bind to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of BChE active site. The synthesized compounds were also evaluated for their in vitro antibacterial and antifungal activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed high activity against both gram positive and gram negative bacteria and fungi.     

Synthesis,bioactivity and molecular modeling studies on potential anti-Alzheimer piperidinehydrazide-hydrazones

A group of N-benzylpiperidine-3/4-carbohydrazide-hydrazones were designed, synthesized and evaluated for acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) activities, Aβ₄₂ self-aggregation inhibitory potentials, and antioxidant capacities, in vitro. All of the compounds displayed eeAChE and huAChE inhibitory activity in a range of IC₅₀ = 5.68–11.35 µM and IC₅₀ = 8.80–74.40 µM, respectively and most of the compounds exhibited good to moderate inhibitory activity on BuChE enzyme. Kinetic analysis and molecular modeling studies were also performed for the most potent compounds (1g and 1j). Not only the molecular modeling studies but also the kinetic analysis suggested that these compounds might be able to interact with the catalytic active site (CAS) and the peripheral anionic site (PAS) of the enzymes. In the light of the results, compound 1g and compound 1j may be suggested as lead compounds for multifunctional therapy of AD.     

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC₅₀ values for AChE and BChE of 57.88–130.75 µM and 8.25–289.0 µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO₂ and CH₃ groups into aniline ring and CF₃ moiety in phenol is translated into lower IC₅₀ values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125 µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.     

Potent inhibition of acetylcholinesterase by sargachromanol I from Sargassum siliquastrum and by selected natural compounds

Six hundred forty natural compounds were tested for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Of those, sargachromanol I (SCI) and G (SCG) isolated from the brown alga Sargassum siliquastrum, dihydroberberine (DB) isolated from Coptis chinensis, and macelignan (ML) isolated from Myristica fragrans, potently and effectively inhibited AChE with IC₅₀ values of 0.79, 1.81, 1.18, and 4.16 µM, respectively. SCI, DB, and ML reversibly inhibited AChE and showed mixed, competitive, and noncompetitive inhibition, respectively, with K_i values of 0.63, 0.77, and 4.46 µM, respectively. Broussonin A most potently inhibited BChE (IC₅₀ = 4.16 µM), followed by ML, SCG, and SCI (9.69, 10.79, and 13.69 µM, respectively). In dual-targeting experiments, ML effectively inhibited monoamine oxidase B with the greatest potency (IC₅₀ = 7.42 µM). Molecular docking simulation suggested the binding affinity of SCI (−8.6 kcal/mol) with AChE was greater than those of SCG (−7.9 kcal/mol) and DB (−8.2 kcal/mol). Docking simulation indicated SCI interacts with AChE at Trp81, and that SCG interacts at Ser119. No hydrogen bond was predicted for the interaction between AChE and DB. This study suggests SCI, SCG, DB, and ML be viewed as new reversible AChE inhibitors and useful lead compounds for the development for the treatment of Alzheimer’s disease.     

Design and Synthesis of Selective Acetylcholinesterase Inhibitors: Arylisoxazole‐Phenylpiperazine Derivatives

In this work, a novel series of arylisoxazole‐phenylpiperazines were designed, synthesized, and evaluated toward acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Our results revealed that [5‐(2‐chlorophenyl)‐1,2‐oxazol‐3‐yl](4‐phenylpiperazin‐1‐yl)methanone ( 5c ) was the most potent AChE inhibitor with IC₅₀ of 21.85 μm . It should be noted that most of synthesized compounds showed no BChE inhibitory activity and [5‐(2‐fluorophenyl)‐1,2‐oxazol‐3‐yl](4‐phenylpiperazin‐1‐yl)methanone ( 5a ) was the most active anti‐BChE derivative (IC₅₀=51.66 μm ). Also, kinetic studies for the AChE and BChE inhibitory activity of compounds 5c and 5a confirmed that they have simultaneously bound to the catalytic site (CS) and peripheral anionic site (PAS) of both AChE and BChE. Furthermore, docking study of compound 5c showed desired interactions of that compound with amino acid residues located in the active and peripheral anionic sites. Compound 5c was also evaluated for its BACE1 inhibitory activity and demonstrated IC₅₀=76.78 μm . Finally, neuroprotectivity of compound 5c on Aβ‐treated neurotoxicity in PC12 cells depicted low activity.