Active Site Of Acetylcholinesterase Research Articles

In vitro and in silico investigation of FDA-approved drugs to be repurposed against Alzheimer's disease.

Alzheimer's disease (AD), one of the main causes of dementia, is a neurodegenerative disorder. Cholinesterase inhibitors are used in the treatment of AD, but prolonged use of these drugs can lead to serious side effects. Drug repurposing is an approach that aims to reveal the effectiveness of drugs in different diseases beyond their clinical uses. In this work, we investigated in vitro and in silico inhibitory effects of 11 different drugs on cholinesterases. The results showed that trimebutine, theophylline, and levamisole had the highest acetylcholinesterase inhibitory actions among the tested drugs, and these drugs inhibited by 68.70 ± 0.46, 53.25 ± 3.40, and 44.03 ± 1.20%, respectively at 1000 µM. In addition, these drugs are bound to acetylcholinesterase via competitive manner. Molecular modeling predicted good fitness in acetylcholinesterase active site for these drugs and possible central nervous systemaction for trimebutine. All of these results demonstrated that trimebutine was determined to be the drug with the highest potential for use in AD.

Anticholinesterase activities of novel isoindolin-1,3-dione-based acetohydrazide derivatives: design, synthesis, biological evaluation, molecular dynamic study

In pursuit of developing novel cholinesterase (ChE) inhibitors through molecular hybridization theory, a novel series of isoindolin-1,3-dione-based acetohydrazides (compounds 8a–h) was designed, synthesized, and evaluated as possible acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. In vitro results revealed IC50 values ranging from 0.11 ± 0.05 to 0.86 ± 0.02 µM against AChE and 5.7 ± 0.2 to 30.2 ± 2.8 µM against BChE. A kinetic study was conducted on the most potent compound, 8a, to ascertain its mode of inhibition, revealing its competitive mode against AChE. Furthermore, the binding interaction modes of the most active compound within the AChE active site was elucidated. Molecular dynamics simulations of compound 8a were performed to assess the stability of the 8a-AChE complex. In silico pharmacokinetic predictions for the most potent compounds indicated their potential as promising lead structure for the development of new anti-Alzheimer’s disease (anti-AD) agents.

Bioactivity and molecular docking studies of selected plant compounds.

The shortcomings of synthetic pesticides are becoming increasingly evident. In the pursuit of looking for alternative, environmentally friendly pesticides, the potential use of two naturally occurring sesquiterpenes, α-bisabolol and bisabolol oxide A, as bactericides or acaricides, was investigated against three gram-positive and three gram-negative bacteria, and the eggs and larvae of the cattle tick Hyalomma scupense, respectively. The primary targeted site of synthetic insecticides is acetylcholinesterase (AChE), so the inhibitory activity of both sesquiterpenes was evaluated. Then, molecular docking and molecular mechanics generalized Born surface area (MM-GBSA)studies were performed to gain insight into their binding mode in the AChE active site. Bisabolol oxide A showed good activity against Staphylococcus aureus, Escherichia coli, and Salmonella enteritidis with inhibition zones ranging from 16 to 34 mm and minimal inhibitory concentration (CIM) of 3.125 mg mL-1. Ovicidal and larvicidal assays revealed promising activity of α-bisabolol and bisabolol oxide A against H. scupense, with bisabolol oxide A being more effective against larval ticks with lethal concentration (LC50) value of 0.78%. Both compounds also displayed potent anti-AChE activity with inhibition concentration (IC50) values of 37.09 and 28.14 μg mL-1, respectively. Furthermore, α-bisabolol and bisabolol oxide A exhibited good and comparable docking scores (-7.289 and -7.139 Kcal mol-1, respectively) and were found to accommodate in the active-site gorge of AChE via hydrogen bonding and hydrophobic interactions. Bisabolol oxide A and, to a lesser degree, α-bisabolol are active against bacteria and ectoparasites and may represent an economical and sustainable alternative to toxic synthetic pesticides to control pathogens. © 2024 Society of Chemical Industry.

The Effect of a Tribulus-Based Formulation in Alleviating Cholinergic System Impairment and Scopolamine-Induced Memory Loss in Zebrafish (Danio rerio): Insights from Molecular Docking and In Vitro/In Vivo Approaches.

Tribulus terrestris L. (Tt) has been recently gaining attention for its pharmacological value, including its neuroprotective activities. In this study, we explore the neuroprotective effects of a Tribulus terrestris extract in a zebrafish (Danio rerio) model of scopolamine (SCOP)-induced memory impairment and brain oxidative stress. SCOP, an anticholinergic drug, was employed to replicate fundamental aspects of Alzheimer's disease (AD) in animal models. The fish were treated with ethanolic leaf extract (ELE) from Tt (1, 3, and 6 mg/L) for 15 days. SCOP (100 µM) was administered 30 min before behavioral tests were conducted. Molecular interactions of the major compounds identified via UPLC-PDA/MS in Tt fractions with the active site of acetylcholinesterase (AChE) were explored via molecular docking analyses. Terrestrosin C, protodioscin, rutin, and saponin C exhibited the most stable binding. The spatial memory performance was assessed using the Y-maze test, and memory recognition was examined using a novel object recognition (NOR) test. Tt extract treatment reversed the altered locomotion patterns that were caused by SCOP administration. Biochemical analyses also verified Tt's role in inhibiting AChE, improving antioxidant enzyme activities, and reducing oxidative stress markers. The present findings pave the way for future application of Tt as a natural alternative to treat cognitive disorders.

Molecular Docking Study of Caffeic Acid as Acetylcholinesterase Inhibitor

Abstract: Acetylcholinesterase (AChE) receptor is a receptor that has been widely used as a potential drug target for Alzheimer's disease. Caffeic acid is a phenolic compound that had been experimentally proven to be an inhibitor of AChE. In this study, 100 molecular docking simulations were performed to study the interaction of caffeic acid in inhibiting AChE. The molecular docking simulations were performed using YASARA software with an in-house developed plug-in. Redocking results showed that there were 99 out of 100 docking poses had an RMSD value of ≤ 2.000 Å, which indicated that the molecular docking procedure could be used for further processes. The molecular docking of caffeic acid showed that all docking poses had an RMSD value of ≤ 2.000 Å relative to the best pose of the first simulation, revealing that there was only one dominant docking pose in the AChE active site. Caffeic acid interacted favorably in the AChE active site with binding energy of about -8.022 kcal/mol. Its interactions were stabilized by hydrophobic and pi-anion interactions, in which some of the interactions resemble the same interaction of the native ligand.
 Keywords: Acetylcholinesterase, Alzheimer's disease, caffeic acid, molecular docking

Combinative effects of akarkara root-derived metabolites on anti-inflammatory and anti-alzheimer key enzymes: integrating bioassay-guided fractionation, GC-MS analysis, and in silico studies

BackgroundAnacyclus pyrethrum L. (Akarkara root), a valuable Ayurvedic remedy, is reported to exhibit various pharmacological activities. Akarkara root was subjected to bioassay-guided fractionation, to isolate its active constituents and discover their potential bioactivities, followed by computational analysis.MethodsThe methanol extract and its fractions, methylene chloride, and butanol, were assessed for their antioxidant, anti-inflammatory, and anticholinergic potentials. The antioxidant activity was determined using DPPH, ABTS, FRAP, and ORAC assays. The in vitro anticholinergic effect was evaluated via acetyl- and butyryl-cholinesterase inhibition, while anti-inflammatory effect weas determined using COX-2 and 5-LOX inhibitory assays. The methylene chloride fraction was subjected to GC/MS analysis and chromatographic fractionation to isolate its major compounds. The inhibitory effect on iNOS and various inflammatory mediators in LPS-activated RAW 264.7 macrophages was investigated. In silico computational analyses (molecular docking, ADME, BBB permeability prediction, and molecular dynamics) were performed.ResultsForty-one compounds were identified and quantified and the major compounds, namely, oleamide (A1), stigmasterol (A2), 2E,4E-deca-2,4-dienoic acid 2-phenylethyl amide (A3), and pellitorine (A4) were isolated from the methylene chloride fraction, the most active in all assays. All compounds showed significant in vitro antioxidant, anticholinergic and anti-inflammatory effects. They inhibited the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in activated RAW macrophages. The isolated compounds showed good fitting in the active sites of acetylcholinesterase and COX-2 with high docking scores. The ADME study revealed proper pharmacokinetics and drug likeness properties for the isolated compounds. The isolated compounds demonstrated high ability to cross the BBB and penetrate the CNS with values ranging from 1.596 to -1.651 in comparison with Donepezil (-1.464). Molecular dynamics simulation revealed stable conformations and binding patterns of the isolated compounds with the active sites of COX-2 and acetyl cholinesterase.ConclusionsUltimately, our results specify Akarkara compounds as promising candidates for the treatment of inflammatory and neurodegenerative diseases.

Novel chalcone derivatives of ursolic acid as acetylcholinesterase inhibitors: Synthesis, characterization, biological activity, ADME prediction, molecular docking and molecular dynamics studies

Acetylcholinesterase (AChE) is a critical target in the prevention of Alzheimer's Disease (AD) progression. With the goal of developing potential acetylcholinesterase inhibitors, a new series chalcone derivatives of ursolic acid (4–11) were synthesized and characterized by means of their NMR, FTIR and HRMS spectral data. hAChE inhibition abilities of all compounds were tested in vitro. Compounds 10, 8 and 7 showed high hAChE inhibitory potential with the IC50 values of 1.82, 4.65 and 5.36 µM respectively. When compared to the standard inhibitor (Galantamine, IC50= 1.96 µM), compound 10 was the most potent derivative. After performing kinetic studies, KM constant and Vmax value of hAChE were determined as 0.059 mM and 0.052 EU/ml respectively. Inhibition type of compound 10 was found as competitive and Ki constant was calculated as 1.31 ± 0.18 µM. The inhibition mechanism of compounds was predicted by molecular docking, MM/GBSA analysis, molecular dynamics simulation and ADME studies. Molecular docking studies showed that compounds 10, 8, and 7 have highest binding scores (-9.235, -8.827, -8.645 kcal/mol, respectively), while the standard inhibitor galantamine exhibited binding score of -5.106 kcal/mol. According to the MM/GBSA analysis, compounds 10 and 7 displayed binding free energies of -46.19 and -49.19 kcal/mol, respectively, which were higher than the standard's binding free energy of -41.82 kcal/mol. Molecular dynamic simulations were confirmed successful placement of the compounds 10, 8 and 7 in the active site of AChE. The in silico ADME predictions indicated that compound 10 has acceptable potency as a drug in treatment of AD.

Synthesis and neuroprotective activity of 3-aryl-3-azetidinyl acetic acid methyl ester derivatives.

A library of 3-aryl-3-azetidinyl acetic acid methyl ester derivatives was prepared from N-Boc-3-azetidinone employing the Horner-Wadsworth-Emmons reaction, rhodium(I)-catalyzed conjugate addition of arylboronic acids, and subsequent elaborations to obtain N-unprotected hydrochlorides, N-alkylated and N-acylated azetidine derivatives. The compounds were evaluated for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, revealing several derivatives to possess AChE inhibition comparable to that of the AChE inhibitor rivastigmine. The binding mode of the AChE inhibitor donepezil and selected active compounds 26 and 27 within the active site of AChE was studied using molecular docking. Furthermore, the neuroprotective activity of the prepared compounds was evaluated in models associated with Parkinson's disease (salsolinol-induced) and aspects of Alzheimer's disease (glutamate-induced oxidative damage). Compound 28 showed the highest neuroprotective effect in both salsolinol- and glutamate-induced neurodegeneration models, and its protective effect in the glutamate model was revealed to be driven by a reduction in oxidative stress and caspase-3/7 activity.

Novel iodoquinazolinones bearing sulfonamide moiety as potential antioxidants and neuroprotectors

In a search for new antioxidants, a set of new iodoquinazolinone derivatives bearing benzenesulfonamide moiety and variable acetamide pharmacophores 5–17 were designed and synthesized. The structures of the synthesized compounds were confirmed based on spectral data. Compounds 5–17 were screened using in vitro assay for their antioxidant potential and acetylcholinesterase (AChE) inhibitory activity. The 2-(6-iodo-4-oxo-3-(4-sulfamoylphenyl)-3,4-dihydroquinazolin-2-ylthio)-N-(pyrazin-2-yl) acetamide 14 was the most active scaffold with potent AChE inhibitory activity. Compound 14 showed relative safety with a median lethal dose of 300 mg/kg (LD50 = 300 mg/kg), in an acute toxicity study. The possible antioxidant and neuroprotective activities of 14 were evaluated in irradiated mice. Compound 14 possessed in vivo AChE inhibitory activity and was able to modify the brain neurotransmitters. It was able to cause mitigation of gamma radiation-induced oxidative stress verified by the decline in Myeloperoxidase (MPO) and increase of glutathione (GSH) levels. Also, 14 restored the alterations in behavioral tests. Molecular docking of 14 was performed inside MPO and AChE active sites and showed the same binding interactions as that of the co-crystallized ligands considering the binding possibilities and energy scores. These findings would support that 14 could be considered a promising antioxidant with a neuromodulatory effect.

Bioassay-guided identification of potential Alzheimer’s disease therapeutic agents from Kaempferol-Enriched fraction of Aframomum melegueta seeds using in vitro and chemoinformatics approaches

Alzheimer's disease (AD) has become a major public health concern and the fifth major cause of death among the aging population globally. In this study, the total phenols and flavonoids contents (TPC and TFC) and in vitro antioxidant actions of the methanol extract and the various fractions of Aframomum melegueta were evaluated using 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, nitric oxide scavenging activity (NO), lipid peroxidation (TBARS) activity and ferric reducing power assay (FRAP). Furthermore, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activities of the two most potent fractions were investigated, and the phytochemicals identified in the ethyl acetate fraction, which had the best antioxidant and cholinesterase inhibitory effects were subjected to chemoinformatics studies. The extract and its fraction had high amounts of TPC and TFC. The ethyl acetate fraction exerted the best DPPH, NO, TBARS, and FRAP inhibition with IC50 values of 5.06, 6.58, 2.12, and 88.73 µg/mL, respectively. Interestingly, n-hexane and ethyl acetate fractions inhibited AChE (IC5016.83 and 11.67 µg/mL) and BuChE (IC50 7.54 and 5.21 µg/mL) enzymatic activities more than the standard inhibitor, rivastigmine which had 11.99 and 11.40 µg/mL IC50 values, respectively. A total of 18 compounds were identified in ethyl acetate fraction, and kaempferol was the major component, with 40.01 µg/g (30%). More strikingly, the top-scoring compounds (catechin, and kaempferol) exhibited good binding affinity, and interacted favorably with amino acids residues around and within the active sites of AChE and BuChE and also obeyed drug-likeness rules, and did not show a tendency towards toxicity when placed side by side with rivastigmine which is immunogenic. Thus, A. melegueta seeds contain safe bioactive chemicals, which could be a veritable remedy for managing Alzheimer's and other neurodegenerative diseases.

Design, docking, synthesis and biological evaluation of chromone derivatives as dual inhibitors of Interleukin‐6 and acetylcholinesterase for treatment of Alzheimer’s Disease

AbstractBackgroundInterleukin‐6 (IL‐6) and acetylcholinesterase (AChE) are two important targets implicated in the progression of Alzheimer’s Disease (AD). Concurrent inhibition of both IL‐6 and AChE by a molecule presents an effective strategy for the treatment of AD. In the present study, novel molecules are designed by coupling a chromone and a N,N‐disubstituted carbamoyl amine as pharmacophore for IL‐6 and AChE inhibition, respectively.MethodFour series (S1‐S4) of 40 compounds are designed by coupling the two selected pharmacophore through alkyl linkers of different lengths (1‐4 carbon atoms). All designed compounds are docked in AChE (PDB 1EVE). The compounds having docking score ±20% of donepezil (the lead molecule) are synthesised, and evaluated for AChE inhibitory activity. The compounds showing >45% inhibition of AChE are further evaluated for IL‐6 inhibitory activity.ResultTwelve best‐fit compounds (AChE docking score >8.3) among all designed compounds are selected for synthesis. The data suggests that a 1‐ or 2‐carbon atom(s) linker is conducive to orient the pharmacophore for optimum binding with AChE active site. The predicted ADME properties of the 12 selected compounds suggest that these can cross the blood brain barrier with good oral bioavailability. These compounds are synthesised and evaluated for anti‐AChE activity. Five compounds, showing >45% inhibition of AChE, are further evaluated for IL‐6 inhibitory activity. Compound S1f is found to be the most potent inhibitor of both AChE and IL‐6 (IC50 0.7 and 0.8 µM, respectively).ConclusionA chromone moiety connected to a piperidine ring through a 1‐carbon atom linker may prove as a useful template for the development of new chemical entities effective against AD.

Molecular docking analysis of acetylcholinesterase inhibitors for Alzheimer's disease management.

Alzheimer's disease (AD) is a neurological disease that is related to aging and is the leading cause of dementia globally. AD has a significant influence on cognitive functions, particularly memory, resulting in a variety of functional deficits. Given the increasing prevalence of AD, there is an urgent need for the development of effective therapeutic therapies. In a quest to uncover a holistic remedy for AD, a total of 41 bioactive compounds derived from three distinct medicinal plant sources were screened to evaluate their potential to inhibit the active sites of acetylcholinesterase (AChE). The insilico screening protocol included 24 licorice-derived compounds, 5 ginkgo biloba-derived compounds, and 11 ginseng-derived compounds. Two compounds (Ginkgolide A and Licorice glycoside D2) were observed to display greater binding energy (BE) relative to the control by interacting with crucial residues in the active site of AChE. Ginkgolide A and Licorice glycoside D2 exhibited BEs of -11.3 and -11.2 kcal/mol, respectively, whereas the control, Donepezil, demonstrated a BE of -10.8 kcal/mol. Further, these compounds exhibit favorable drug-likeness properties. This study suggests that further experimental investigations can be conducted on Ginkgolide A and Licorice glycoside D2 to explore their potential therapeutic applications for AD.

Synthesis, in silico study, and biological evaluation of cyclosulfamide derivatives as new anticholinesterase inhibitors

After the great spread of Alzheimer's disease (AD) in the past few years, many researchers directed their work toward developing an effective treatment for this disease and to discovering very advanced drugs. Cyclosulfamides are considered as versatile pharmacophores in the construction of new molecules with excellent activities. Therefore, a series of cyclosulfamide have been synthesized and evaluated as anti-Alzheimer agents through in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition. Most of tested compounds showed an average inhibitory activity against two targeted enzymes compared with the reference ligand. Specifically, 10a showed the best inhibition of AChE enzyme with an IC50 = 45.30±0.88 µM; while 4a exhibited the most potent BuChE enzyme inhibition with an IC50 = 52.87±3.73 µM.Further, we were able to determine a feasible binding mode for cyclosulfamide derivatives owing to molecular docking studies, which offered prospective evidence to identify significant interactions between the active site of AChE and the synthesized ligands.Following the encouraging findings of the molecular docking investigation, the complex AChE-10a was put through a 100 ns Desmond of Schrodinger simulation of molecular dynamics (MD), during which the receptor-ligand combination showed significant stability after 10 ns of MD simulation.

Kinetic Studies, Antioxidant Activities, Enzyme Inhibition Properties and Molecular Docking of 1,3-Dihydro-1,3-Dioxoisoindole Derivatives

The acid catalyzed hydrolysis of the N-(p-substitutedphenyl) phthalimides in three different acids was investigated at 50.0±0.1°C. Two different antioxidant activity tests as DPPH• and ABTS•+ scavenging activities, and three various enzyme inhibition activity tests as urease, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibition activities, were applied. Compound 3c (2.03 µg/mL ) has higher antioxidant activity than other compounds and standards according to DPPH test. In AChE assay, compounds 3a and 3b (13.13 and 9.59 µg/mL) has higher enzyme inhibition activity than the standard Galantamine (14.37 µg/mL). In BChE and urease tests, all compounds (6.84-13.60 and 10.49-17.73 µg/mL) have higher enzyme inhibition activity than the standard Galantamine (49.40 µg/mL) and thiourea (26.19 µg/mL), respectively. The molecule interaction for each of the three compounds with the active sites of AChE, BChE, and urease enzymes was examined via molecular docking simulations.

Synthesis, in vitro bio-evaluation, and molecular docking study of thiosemicarbazone-based isatin/bis-Schiff base hybrid analogues as effective cholinesterase inhibitors

Analogues of isatin/bis-Schiff bases based on thiocarbohydrazone (1–16) were synthesized, characterised using various methods like NMR and HR-ESI-MS, and then tested against the acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. All analogues showed good inhibitory potentials ranging from 0.20 ± 0.05 to 7.40 ± 0.20 M (for AChE) and 0.50 ± 0.05 to 9.40 ± 0.10 M (for BuChE) as compared to the reference drug Donepezil (IC50 = 2.16 ± 0.12 & 4.5 ± 0.11 M respectively). Analogue 1 was shown to be the most effective inhibitor of the AChE and BuChE enzymes among the synthesised analogues. The reason for Analogue 1 may be due to the role played by oxygen and the nitro motif in H-bonding with the active sites of AChE and BuChE enzymes. A structure–activity relationship (SAR) was developed based on nature, position, number, and the electron-donating and -withdrawing effects of substitution(s) on phenyl rings. Molecular docking studies were used to describe the binding interactions of the most active inhibitors with the active sites of AChE and BuChE.

Para-Substituted Thiosemicarbazones as Cholinesterase Inhibitors: Synthesis, In Vitro Biological Evaluation, and In Silico Study.

The current research reports the synthesis of 14 para-substituted thiosemicarbazone derivatives in good to excellent yields using standard procedures. Initially, 4-ethoxybenzaldehyde (1) and 4-nitrobenzaldehyde (2) were refluxed with thiosemicarbazide in the presence of acetic acid in ethanol for 4-5 h. Then, various substituted phenacyl bromides were treated with the desired thiosemicarbazones (3 and 4) in the presence of triethylamine in ethanol with constant stirring for 5-6 h. The resulting derivatives were confirmed through electron impact mass spectrometry and 1H NMR spectroscopy and evaluated for anticholinesterase inhibitory activity. Among the series, four compounds, 19, 17, 7, and 6, showed potent inhibitory activity against the acetylcholinesterase (AChE) enzyme, having IC50 values of 110.19 ± 2.32, 114.57 ± 0.15, 140.52 ± 0.11, and 160.04 ± 0.02 μM, respectively, compared with standard galantamine (IC50 = 104.5 ± 1.20 μM). Similarly, compounds 19 (IC50 = 145.11 ± 1.03 μM), 9 (IC50 = 147.20 ± 0.09 μM), 17 (IC50 = 150.36 ± 0.18 μM), and 6 (IC50 = 190.21 ± 0.13 μM) were the most excellent inhibitors of butyrylcholinesterase (BChE) when compared with the standard drug galantamine (IC50 = 156.8 ± 1.50 μM). In silico studies were accomplished on the produced derivatives in order to explain the binding interface of compounds with the active sites of AChE and BChE enzymes.

Divulging the anti-acetylcholinesterase activity of Colletotrichum lentis strain KU1 extract as sustainable AChE active site inhibitors.

Alzheimer's disease (AD), also called senile dementia is a neurodegenerative disease seen commonly in the elderly and is characterised by the formation of β-amyloid plaques and neurofibrillary tangles (NFT). Though a complete understanding of the disease is lacking, recent studies showed the role of the enzyme acetylcholinesterase (AChE) in pathogenesis. Finding new lead compounds from natural sources has always been a quest for researchers. Endophytic fungi are a set of microbes that reside within plants without causing any harm. This study focuses on screening endophytes for the production of active acetylcholinesterase inhibitors. Five endophytic fungi were isolated from Catharanthus roseus and screened for AChE inhibitory activity. Three isolates were found to inhibit AChE inhibitory activity and were distinguished based on molecular and microscopic methods. The mycelial extract was taken for the bioassay-guided column chromatography and TLC was performed on the active fraction. The GC-MS and NMR analysis identified the active compounds in the extract as 9-hexadecen-1-ol and erucamide. Molecular docking studies revealed that the compounds are thermodynamically feasible and have significant glide scores. Computational studies revealed that the hydroxyl group of 9-hexadecen-1-ol forms a hydrogen bond with Ser 293 in the active site of AChE, whereas the active site interactions were predominantly hydrophobic in the case of erucamide and are reflected in AChE inhibition assays.

Exploring the Inhibition of Quercetin on Acetylcholinesterase by Multispectroscopic and In Silico Approaches and Evaluation of Its Neuroprotective Effects on PC12 Cells.

This study investigated the inhibitory mechanism of quercetin in acetylcholinesterase (AChE) and its neuroprotective effects on β-amyloid25-35-induced oxidative stress injury in PC12 cells. Quercetin inhibited AChE in a reversible mixed manner with an IC50 of 4.59 ± 0.27 µM. The binding constant of quercetin with AChE at 25 °C was (5.52 ± 0.05) × 104 L mol-1. Hydrogen bonding and van der Waals forces were the main interactions in forming the stable quercetin-AChE complex. Computational docking revealed that quercetin was dominant at the peripheral aromatic site in AChE and induced enzymatic allosterism; meanwhile, it extended deep into the active center of AChE and destabilized the hydrogen bond network, which caused the constriction of the gorge entrance and prevented the substrate from entering the enzyme, thus resulting in the inhibition of AChE. Molecular dynamics (MD) simulation emphasized the stability of the quercetin-AChE complex and corroborated the previous findings. Interestingly, a combination of galantamine hydrobromide and quercetin exhibited the synergistic inhibition effect by binding to different active sites of AChE. In a β-amyloid25-35-induced oxidative stress injury model in PC12 cells, quercetin exerted neuroprotective effects by increasing the glutathione level and reducing the malondialdehyde content and reactive oxygen species levels. These findings may provide novel insights into the development and application of quercetin in the dietary treatment of Alzheimer's disease.

New acetylcholinesterase inhibitors isolated from Delphinium uncinatum

The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is presently the most common pharmacological approach available for Alzheimer’s disease (AD). Despite research on the molecular bases of AD, potent therapeutic agent against its expansion is still needed. In searching for natural cholinesterase inhibitors, the present study was focused on the isolation of three new norditerpenoid alkaloids, uncinatine B-D together with known virescenine from Delphinium uncinatum. Chemical structures for all the isolated norditerpenoids (1–4) were established using latest spectroscopic techniques. The isolated undescribed compounds along with known virescenine were testified for their acetylcholinesterase inhibitory activity supported by docking analyses. Molecular docking simulation showed that the isolated compounds (1–4) were observed to adhered in the active site of AChE with docking scores − 13.5322 (1), −11.8173 (2), −12.4240 (3) and − 8.9352 (4) respectively. Overall results demonstrated that these natural norditerpenoids compounds were found as selective inhibitors of AChE. This is the first report regarding the use of bioactive ingredients of Delphinium uncinatum in testing against Alzheimer's disease.

Synthesis, Biological Evaluation and Docking Study of Mono- and Di-Sulfonamide Derivatives as Antioxidant Agents and Acetylcholinesterase Inhibitors.

Mono(M1-M5)- and di(DM1-DM5)-sulfonamide derivatives were synthesized by the reaction of 4-iodobenzenesulfonyl chloride compound and aniline derivatives in basic medium. The structures of sulfonamide derivatives were characterized by spectroscopic and X-ray diffraction methods. All compounds were screened for acetylcholinesterase (AChE) inhibitory studies and 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging activities. Among the compounds tested, compound M1 showed the best activity against both AChE (IC50 =42.09 μg/mL for AChE) and DPPH (IC50 =9.94 μg/mL for DPPH). By placing compounds at the active site of AChE, their binding energies and modes were determined. Docking studies were performed in order to investigate binding interaction between the synthesized compounds and AChE. The most active M1 compound showed its low CDOCKER energy (-65,834 kcal/mol).