Potent Cholinesterase Inhibitor Research Articles

Synthesis and molecular docking simulation of new benzimidazole-thiazole hybrids as cholinesterase inhibitors.

Dementia is a cognitive disturbance that is generally correlated with central nervous system diseases, especially Alzheimer's disease. The limited number of medications available is insufficient to improve the lifestyle of the patients suffering from this disease. Thus, new benzimidazole-thiazole hybrids (3-10) were designed and synthesized as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory agents. The in vitro evaluation displayed that the derivatives 4b, 4d, 5b, 6a, 7a, and 8b demonstrated dual inhibitory efficiency against both AChE with IC50 ranging from 4.55 to 8.62 µM and BChE with IC50 ranging from 3.50 to 8.32 µM. By analyzing the Lineweaver-Burk plot, an uncompetitive form of inhibition was determined for the highly active compound 4d, revealing its inhibition type. The human telomerase reverse transcriptase-immortalized retinal pigment epithelial cell linewas used to ensure the safety of the most potent cholinesterase inhibitors. Furthermore, compounds 4b, 4d, 5b, 6a, 7a, and 8b were evaluated for their neuroprotective and antioxidant properties, as well as their ability to suppress COX-2. The results demonstrated that compounds 4d, 5b, and 8b presented significant neuroprotection efficiency against H2 O2 -induced damage in SH-SY5Y cells with % cell viability of 67.42 ± 7.90%, 62.51 ± 6.71%, and 72.61 ± 8.10%, respectively, while the tested candidates did not reveal significant antioxidant activity. Otherwise, compounds 4b, 6a, 7a, and 8b displayed outstanding COX-2 inhibition effects with IC50 ranging from 0.050 to 0.080 μM relative to celecoxib (IC50 = 0.050 µM). In addition, molecular docking was carried out for the potent benzimidazole-thiazole hybrids with the active sites of both AChE (PDB ID: 4EY7) and BChE (PDB code: 1P0P). The tested candidates fit well in the active sites of both portions, with docking scores ranging from -8.65 to -6.64 kcal/mol (for AChE) and -8.71 to -7.73 kcal/mol (for BChE). In silico results show that the synthesized benzimidazole-thiazole hybrids have good physicochemical and pharmacokinetic properties with no Lipinski rule violations. The preceding results exhibited that compound 4d could be used as a new template for developing more significant cholinesterase inhibitors in the future.

Comparative Study of Chemical Composition and Cholinesterase Inhibition Potential of Essential Oils Isolated from Artemisia Plants from Croatia

The essential oil (EO) of Artemisia plants contains a large number of bioactive compounds that are widely used. The aim of this study was to analyse the chemical composition of EOs of six Artemisia plants collected in Croatia and to test their cholinesterase inhibitory potential. GC–MS analysis of the EO of A. absinthium showed that the dominant compounds are cis-sabinyl acetate and cis-epoxy-ocimene; in EO of A. abrotanum, it is borneol; in the EO of A. annua, they are artemisia ketone, camphor and 1,8-cineole; in the EO of A. arborescens, they are camphor and chamazulene; in the EO of A. verlotiorum, they are cis-thujone, 1,8-cineole and trans-thujone; and in the EO of A. vulgaris, they are trans-thujone and trans-epoxy-ocimene. The EO of the five studied Artemisia species from Croatia is rich in monoterpenoid compounds (1,8-cineole, artemisia ketone, cis-thujone, trans-thujone, cis-epoxy-ocimene, camphor, borneol and cis-sabinyl acetate). The EO of A. arborescens is also rich in chamazulene. The results also showed that the tested EOs have moderate cholinesterase inhibition potential, especially the EOs of A. annua, A. vulgaris and A. abrotanum. This is the first analysis of the chemical composition of the EOs of four Artemisia plants and the first analysis of cholinesterase potential for plants collected in Croatia.

Pyrimidine-morpholine hybrids as potent druggable therapeutics for Alzheimer’s disease: Synthesis, biochemical and in silico analyses

The identification of effective and druggable cholinesterase inhibitors to treat progressive neurodegenerative Alzheimer’s disorder remains a continuous drug discovery hunt. In this perspective, the present study investigates the design and discovery of pyrimidine-morpholine hybrids (5a-l) as potent cholinesterase inhibitors. Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction was employed to introduce the structural diversity on the pyrimidine heterocyclic core. A range of commercially available boronic acids was successfully coupled showing a high functional group tolerance. In vitro cholinesterase inhibitory potential using Ellman’s method revealed significantly strong potency. Compound 5h bearing a meta-tolyl substituent at 2-position of pyrimidine ring emerged as a lead candidate against AChE with an inhibitory potency of 0.43 ± 0.42 µM, ∼38-fold stronger value than neostigmine (IC50 = 16.3 ± 1.12 µM). Compound 5h also showed the lead inhibition against BuChE with an IC50 value of 2.5 ± 0.04 µM. The kinetics analysis of 5h revealed the non-competitive mode of inhibition against AChE whereas computational modelling results of potent leads depicted diverse contacts with the binding site amino acid residues. Molecular dynamics simulations revealed the stability of biomolecular system, while, ADME analysis demonstrated druglikeness behaviour of potent compounds. Overall, the investigated pyrimidine-morpholine scaffold presented a remarkable potential to be developed as efficacious anti-Alzheimer’s drugs.

Solvents and detergents compatible with enzyme kinetic studies of cholinesterases

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes that serve a wide range of physiological functions including the hydrolysis of the neurotransmitter acetylcholine and several other xenobiotics. The development of inhibitors for these enzymes has been the focus for the treatment of several conditions, such as Alzheimer's disease. Novel chemical entities are evaluated as potential inhibitors of AChE and BChE using enzyme kinetics. A common issue encountered in these studies is low aqueous solubility of the possible inhibitor. Additives such as cosolvents or detergents can be included in these studies improve the aqueous solubility. Typical cosolvents include acetonitrile or dimethyl sulfoxide while typical detergents include Polysorbate 20 (Tween 20) or 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate (CHAPS). When solubility is not improved, these molecules are often not evaluated further. To address this issue eleven cosolvents and six detergents that could facilitate aqueous solubility were evaluated to understand how they would affect cholinesterase enzymes using Ellman's assay. These studies show that propylene glycol, acetonitrile, methanol, Tween 20, Polysorbate 80 (Tween 80), polyoxyethylene 23 lauryl ether (Brij 35) and polyoxyethylene 10 oleoyl ether (Brij 96v) have the least inhibitory effects towards cholinesterase activity. It is concluded that these cosolvents and detergents should be considered as solubilizing agents for evaluation of potential cholinesterase inhibitors with low aqueous solubility.

Synthesis, molecular docking, and bioactivity study of isoquinoline-sulfonamide hybrid analogues: A promising acetylcholinesterase and butyrylcholinesterase inhibitor candidate

Isoquinoline-sulfonamide hybrid analogues (1–11) were synthesised and tested for their dual cholinesterase inhibitory potentials. All analogues showed a varied degree of inhibitory potential, with IC50 values ranging between 0.30 ± 0.05 to 26.30 ± 0.20 µM (AChE) and 0.80 ± 0.01 to 37.60 ± 0.70 µM (BuChE) as compared to standard drug donepezil (IC50 = 2.16 ± 0.12 and 4.5 ± 0.11 µM respectively). In case of AChE, analogue 2 (IC50 = 0.30 ± 0.05 μM) was most potent, while in case of BuChE, analogues 2, 11, and 5 with IC50 values of 0.80 ± 0.01, 1.20 ± 0.05 and 2.50 ± 0.10 μM respectively, were found most potent. Structure-activity relationship was investigated, which is primarily depending upon nature, number, position, and electron donating/withdrawing effect on phenyl ring. A molecular docking study was carried out to determine the binding interactions of the most potent analogues with the active site of enzymes. The compounds were synthesized by simple modes of synthesis like esterification, hydrazide and finally sulfonamide formation.

Phytochemical Profile, Antioxidant Activity and Cholinesterase Inhibition Potential of Essential Oil and Extracts of Teucrium montanum from Bosnia and Herzegovina

Bioactive compounds from plants play an important role in slowing many neurodegenerative diseases, such as Alzheimer’s disease, by inhibiting cholinesterase enzymes. Studies have shown that oxidative stress is associated with the development of Alzheimer’s disease. In traditional medicine of Bosnia and Herzegovina, Teucrium montanum is used to treat numerous diseases. The chemical composition and biological activity of the essential oil (EO) and aqueous (AE) and methanol extract (ME) of this plant were studied. The chemical composition of EO was studied using GC-MS, while the composition of the extracts was studied using HPLC-DAD. Antioxidant activity was tested using the DPPH and FRAP methods. The protection of lipids and proteins from oxidation was tested using the ammonium thiocyanate and BSA oxidation methods. The ability to inhibit cholinesterases was tested by the Ellman method. The main identified EO compounds were α-cadinol, ß-selinene, δ-cadinene, epi-α-cadinol, germacrene D-4-ol, and α-pinene. The main phenolic compounds of the extracts were p-coumaric acid, ellagic acid and caffeic acid. The tested extracts showed good antioxidant radical scavenging and reducing potential and a very good ability to protect lipids and proteins from oxidation. The EO showed moderate AChE and BChE inhibition potential, while the extracts showed weak or no ability.

Multi-combined QSAR, molecular docking, molecular dynamics simulation, and ADMET of Flavonoid derivatives as potent cholinesterase inhibitors

In searching for a new and efficient therapeutic agent against Alzheimer’s disease, a Quantitative structure-activity relationship (QSAR) was derived for 45 Flavonoid derivatives recently synthesized and evaluated as cholinesterase inhibitors. The multiple linear regression method (MLR) was adopted to develop an adequate mathematical model that describes the relationship between a variety of molecular descriptors of the studied compounds and their biological activities (cholinesterase inhibitors). Golbraikh and Tropsha criteria were applied to verify the validity of the built model. The built MLR model was statistically reliable, robust, and predictive (R2 = 0.801, Q2 cv = 0.876, R2 test = 0.824). Dreiding energy and Molar Refractivity were the major factors that govern the Anti-cholinesterase activity. These results were further exploited to design a new series of Flavonoid derivatives with higher Anti-cholinesterase activities than the existing ones. Thereafter, molecular docking and molecular dynamic studies were performed to predict the binding types of the designed compounds and to investigate their stability at the active site of the Butyrylcholinestérase BuChE protein. The negative and low binding affinity calculated for all designed compounds shows that designed compound 1 has a favorable affinity for the 4TPK. Moreover, molecular dynamics simulation studies confirmed the stability of designed compound 1 in the active pocket of 4TPK over 100 ns. Finally, the ADMET analysis was incorporated to analyze the pharmacokinetics and toxicity parameters. The designed compounds were found to meet the ADMET descriptor criteria at an acceptable level having respectable intestinal permeability and water solubility and can reach the intended destinations. Communicated by Ramaswamy H. Sarma

Evaluation of 4-aminoquinoline derivatives with an n-octylamino spacer as potential multi-targeting ligands for the treatment of Alzheimer's disease

The most successful therapeutic strategy in the treatment of Alzheimer's disease (AD) is directed toward increasing levels of the neurotransmitter acetylcholine (ACh) by inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), the enzymes responsible for its hydrolysis. In this paper, we extended our study on 4-aminoquinolines as human cholinesterase inhibitors on twenty-six new 4-aminoquinolines containing an n-octylamino spacer on C(4) and different substituents on the terminal amino group. We evaluated the potency of new derivatives to act as multi-targeted ligands by determining their inhibition potency towards human AChE and BChE, ability to chelate biometals Fe, Cu and Zn, ability to inhibit the action of β-secretase 1 (BACE1) and their antioxidant capacity. All of the tested derivatives were very potent inhibitors of human AChE and BChE with inhibition constants (Ki) ranging from 0.0023 to 1.6 μM. Most of the compounds were estimated to be able to cross the blood-brain barrier (BBB) by passive transport and were nontoxic to human neuronal, kidney and liver cells in concentrations in which they inhibit cholinesterases. Generally, newly synthesised compounds were weak reductants compared to standard antioxidants, but all possessed a certain amount of antioxidant activity compared to tacrine. Of the eleven most potent cholinesterase inhibitors, eight compounds also inhibited BACE1 activity at 10–18%. Based on our overall results, compounds 8 with 3-fluorobenzyl, 11 with 3-chlorobenzyl and 17 with 3-metoxy benzyl substituents on the terminal amino group stood out as the most promising for the treatment of AD; they strongly inhibited AChE and BChE, were non-toxic on HepG2, HEK293 and SH-SY5Y cells, had the potential to cross the BBB and possessed the ability to chelate biometals and/or inhibit the activity of BACE1 within a range close to the therapeutically desired degree of inhibition.

Synthesis and cholinesterase inhibitory potential of 2-phenoxy-N-substituted-acetamide derivatives

The research studies worldwide on the identification of novel molecules having the potential to inhibit cholinesterase enzymes generated many compounds with promising results for some of them. Since there are limited number of drugs used in the treatment of Alzheimer's Disease in particular, the research studies continue. Within the scope of this study, four 2-phenoxy-N-substituted-acetamide derivatives were synthesized and their structures were identified employing spectroscopic techniques. The title molecules were further evaluated for their cholinesterase inhibitory potential in modified Ellman’s method. The results displayed that the compounds have moderate activity and the simple scaffold employed might be used in future studies for more promising compounds.

Synthesis, in silico and in vitro studies of hydrazide-hydrazone imine derivatives as potential cholinesterase inhibitors.

A series of hydrazide-hydrazone imine derivative compounds (3a-k) were synthesized and their structures characterized using FTIR, 1 H, and 13 C (NMR) spectroscopic methods. In addition, molecular structures of compounds 3a, 3d, and 3g were elucidated by X-ray diffraction technique. In vitro inhibition activities of hydrazide-hydrazone imine derivatives against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were investigated. Compound 3i (IC50 = 2.01 μM) exhibited the best inhibitory activity against AChE, comparable to the control Galantamine (IC50 = 2.60 μM). Against BChE, compound 3h (IC50 = 2.83 μM) showed the best inhibitory property which is higher control Galantamine (IC50 = 3.70 μM). The Ki values of compound 3i (Ki = 0.63 μM) and compound 3h (Ki = 0.94 μM) that have the strongest inhibitory potential were determined against AChE and BChE, respectively. According to the docking result, the most stable conformation of AChE and compound 3i showed that it has a binding affinity of -10.82 kcal/moL. The binding affinity of the most stable conformation formed by BChE and compound 3h is -8.60 kcal/moL. Finally, in silico results and pharmacokinetic parameters of ADME showed that these compounds have good oral bioavailability properties.

Molecular docking and dynamics simulation approach of Camellia sinensis leaf extract derived compounds as potential cholinesterase inhibitors.

Molecular docking and dynamics simulation approach of Camellia sinensis leaf extract derived compounds as potential cholinesterase inhibitors.

Highly functionalized dispiropyrrolidine embedded indandione hybrids as potent cholinesterase inhibitors

New class of highly functionalized dispiropyrrolidine tethered indandione heterocycles in good yield were obtained through stereo- and regioselective single-pot three component cycloaddition methodology between benzylidene-indandione and non-stabilized azomethine ylide. The ylide generated from active diketone and aminophenylpropanoic acid via dehydration/decarboxylative pathway. The synthesized dispiropyrroldine comprising indandiones were elucidated through 1H and 13C NMR spectroscopic analysis, the stereo and regioselective formation of the dispiropyrrolidine were unequivocally assigned by X-ray diffraction analysis. Compound thus synthesized were assayed as potential inhibitor for the treatment of AD. Spiropyrrolidine 4h that bearing methoxy group on the phenyl ring showed significant activity, IC50 of 3.24 ± 0.25 and 10.25 ± 0.16 μM against acetyl and butyryl cholinesterase enzyme, respectively. The lead compound 4h executed to investigate for their docking simulation that showed strong binding affinity with binding site of the cholinesterase protein.

Discovery of novel dual acetylcholinesterase and butyrylcholinesterase inhibitors using machine learning and structure-based drug design

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are crucial targets that catalyse the breakdown of acetylcholine (ACh) and are implicated in the pathogenesis of Alzheimer's disease (AD). Thus, the development of cholinesterase (AChE and BChE) inhibitors with a novel scaffold is an effective way to intervene in the pathogenesis of AD. This study used a multistep virtual screening method combined with machine learning (ML) models and structural bioinformatics to identify a novel dual acetylcholinesterase and butyrylcholinesterase inhibitor from the Maybridge database. Finally, five common hits (AW00462, AW00794, MWP01235, SCR00709, CD05692) were found after a consensus analysis of classification models and multistep screening protocol which showed their potential against AChE and BChE enzymes. Further, MM/GBSA free energy calculation and MD simulation studies predicted CD05692 as a potential inhibitor, which formed stable interactions with the active site residues compared with the other compounds. The docking score of CD05692 was found maximum negative (AChE= -15.03 Kcal/mole; BChE= -7.07 Kcal/mole) compared with the other identified hits. The MM/GBSA binding free energy ∆G (AChE= -76.34 Kcal/mole; BChE= -74.72 Kcal/mole) and the HOMO orbital energy (-0.352,410 eV) was also predicted to be in favour of CD05692. The in silico pharmacokinetic investigations also ascertained its drug likeliness properties. Finally, compound CD05692 was synthesised, characterized and evaluated in vitro for ChE (hAChE and hBChE) inhibitory potential. The IC50 value of the lead CD05692 has shown good hAChE inhibition (IC50 = 0.927 ± 0.019 µM) and moderate hBChE inhibition (IC50 = 6.377 ± 0.038 µM). Thus, based on this study, we proposed that CD05692 could further be optimized as a lead to design potential cholinesterase inhibitors to combat AD.

Potent heteroaromatic hydrazone based 1,2,4-triazine motifs: synthesis, anti-oxidant activity, cholinesterase inhibition, quantum chemical and molecular docking studies

1,2,4-Triazine based hydrazone scaffolds possessing impressive biological activities are synthesized using heteroaromatic aldehydes. The target molecules were characterized by detailed spectroscopic techniques. Anti-oxidant capacities of target compounds were determined using DPPH free radical scavenging activity, ABTS method and superoxide anion scavenging assay by means of NBT. Compound 4a displayed potent anti-oxidant potential against ABTS having IC50 28.09 ± 0.15 µM comparative to the standard Trolox (26.01 ± 0.02 µM). Cholinesterase inhibitory potentials of the synthesized compounds were also evaluated, where compound 4b intensely inhibited against AChE and BChE in dose dependent method compared to standard drugs, allanzanthane and galantamine. The IC50 value of compound 4b for AChE was 15.24 ± 0.03 µM vs 10.13 ± 0.01 for allanzanthane and 13.01 ± 0.02 for galantamine, whereas, IC50 value of 4b for BChE was 17.01 ± 0.6 µM vs 22.00 ± 0.01 for allanzanthane and 26.02 ± 0.09 for galantamine. Density functional theory (DFT) simulations of synthesized compounds (4a-c) complement the experimental spectroscopic data (FTIR, 1H & 13C NMR & UV–Visible). The HOMO-LUMO energy gaps of 3.58 eV to 3.80 eV reflect the kinetic stability of the compounds (4a-c). Moreover, the MEP analysis confirmed the chemical reactivities of these compounds and more nucleophilic sites were identified at the heteroatoms of heterocyclic moiety and triazine moiety. In silico molecular docking study revealed that our active targeted compounds have minimum binding energy and good affinity toward the active pocket of target protein. These results showed that our synthesized compounds are excellent inhibitors of AChE & BChE enzymes, and therefore, can be subjected to further studies in order to accomplish potent drug responsible for the treatment of Alzheimer's disease.

Ultrasound-Assisted Synthesis of Piperidinyl-Quinoline Acylhydrazones as New Anti-Alzheimer's Agents: Assessment of Cholinesterase Inhibitory Profile, Molecular Docking Analysis, and Drug-like Properties.

Alzheimer's disease (AD) is one of the progressive neurological disorders and the main cause of dementia all over the world. The multifactorial nature of Alzheimer's disease is a reason for the lack of effective drugs as well as a basis for the development of new structural leads. In addition, the appalling side effects such as nausea, vomiting, loss of appetite, muscle cramps, and headaches associated with the marketed treatment modalities and many failed clinical trials significantly limit the use of drugs and alarm for a detailed understanding of disease heterogeneity and the development of preventive and multifaceted remedial approach desperately. With this motivation, we herein report a diverse series of piperidinyl-quinoline acylhydrazone therapeutics as selective as well as potent inhibitors of cholinesterase enzymes. Ultrasound-assisted conjugation of 6/8-methyl-2-(piperidin-1-yl)quinoline-3-carbaldehydes (4a,b) and (un)substituted aromatic acid hydrazides (7a-m) provided facile access to target compounds (8a-m and 9a-j) in 4-6 min in excellent yields. The structures were fully established using spectroscopic techniques such as FTIR, 1H- and 13C NMR, and purity was estimated using elemental analysis. The synthesized compounds were investigated for their cholinesterase inhibitory potential. In vitro enzymatic studies revealed potent and selective inhibitors of AChE and BuChE. Compound 8c showed remarkable results and emerged as a lead candidate for the inhibition of AChE with an IC50 value of 5.3 ± 0.51 µM. The inhibitory strength of the optimal compound was 3-fold higher compared to neostigmine (IC50 = 16.3 ± 1.12 µM). Compound 8g exhibited the highest potency and inhibited the BuChE selectively with an IC50 value of 1.31 ± 0.05 µM. Several compounds, such as 8a-c, also displayed dual inhibitory strength, and acquired data were superior to the standard drugs. In vitro results were further supported by molecular docking analysis, where potent compounds revealed various important interactions with the key amino acid residues in the active site of both enzymes. Molecular dynamics simulation data, as well as physicochemical properties of the lead compounds, supported the identified class of hybrid compounds as a promising avenue for the discovery and development of new molecules for multifactorial diseases, such as Alzheimer's disease (AD).

Natural Inhibitors of Cholinesterases: Chemistry, Structure-Activity and Methods of Their Analysis.

This article aims to provide an updated description and comparison of the data currently available in the literature (from the last 15 years) on the studied natural inhibitors of cholinesterases (IChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These data also apply to the likely impact of the structures of the compounds on the therapeutic effects of available and potential cholinesterase inhibitors. IChEs are hitherto known compounds with various structures, activities and origins. Additionally, multiple different methods of analysis are used to determine the cholinesterase inhibitor potency. This summary indicates that natural sources are still suitable for the discovery of new compounds with prominent pharmacological activity. It also emphasizes that further studies are needed regarding the mechanisms of action or the structure-activity correlation to discuss the issue of cholinesterase inhibitors and their medical application.

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.

Design, Synthesis, and Biological Evaluation of Some Benzothiazolone Derivatives as Cholinesterase Inhibitors

AbstractIn this study, nine new benzothiazolone derivatives (6 a–i) were designed and synthesized to identify potent cholinesterase inhibitors. The compounds were tested in vitro against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and found to be selective to BChE. Compound 6 f proved the most potent derivative (IC50=12.25±0.23 μM) against BChE and was identified as a mixed‐type inhibitor with a Ki value of 4.45±0.35 μM according to the kinetic studies. Molecular modelling suggested that the derivatives were druglike and non‐PAINS. Compound 6 f showed good fit in BChE active site interacting with the key sites important for enzyme activity according to the molecular docking study.

Ex Vivo Antioxidant and Cholinesterase Inhibiting Effects of a Novel Galantamine–Curcumin Hybrid on Scopolamine-Induced Neurotoxicity in Mice

Oxidative stress is an essential factor in the development and progression of Alzheimer's disease (AD). An excessive amount of reactive oxygen species (ROS) induces the peroxidation of lipid membranes, reduces the activity of antioxidant enzymes and causes neurotoxicity. In this study, we investigated the antioxidant and cholinesterase inhibitory potential of a novel galantamine-curcumin hybrid, named 4b, administered orally in two doses (2.5 mg/kg and 5 mg/kg) in scopolamine (SC)-induced neurotoxicity in mice. To evaluate the effects of 4b, we used galantamine (GAL) (3 mg/kg) and curcumin (CCN) (25 mg/kg) as positive controls. Ex vivo experiments on mouse brains showed that the higher dose of 4b (5 mg/kg) increased reduced glutathione (GSH) levels by 46%, catalase (CAT) and superoxide dismutase (SOD) activity by 57%, and glutathione peroxidase (GPx) activity by 108%, compared with the SC-treated group. At the same time, 4b (5 mg/kg) significantly reduced the brain malondialdehyde (MDA) level by 31% and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities by 40% and 30%, respectively, relative to the SC-impaired group. The results showed that 4b acted as an antioxidant agent and brain protector, making it promising for further experimental research in the field of neurodegenerative diseases.

Design, synthesis and SAR studies of novel tacrine derivatives as potent cholinesterase inhibitors

A series of tacrine-2-amide derivatives were synthesized and biologically evaluated for their acetylcholinesterase (AChE) inhibition studies. All synthesized compounds showed a good potency less than 100 ​nM. Of 11 analogues compounds 7b, 8a and 8c were found to exhibit good potency of 23.66 ​nM, 20 ​nM and 24.33 ​nM towards inhibition of acetylcholinesterase, respectively. Insilico study revealed that these compounds can bind strongly in catalytic active site (CAS) as well as peripheral active site (PAS) of enzyme. The docking results stated that the π-π stacking interaction, have a significant role in the protein-ligand binding and provide information about the binding enthalpy. The compound 7b shows good affinity with AChE, and possess a glide score of −10.38 ​kcal/mol and having a binding energy of −24.03 ​kcal/mol. The compound 7b showed interaction with Tyr341 and forming π-π stacking with Trp86. The compound 8a shows a glide score of −11.22 ​kcal/mol with a binding energy of −30.88 ​kcal/mol which is contributed by π-π stacking interaction with Trp86, and a hydrogen bond with amino group of tacrine with His447. The compound 8c showed a better glide score of −12.81 with binding affinity of −59.90 ​kcal/mol.