Structures of human acetylcholinesterase bound to dihydrotanshinone I and territrem B show peripheral site flexibility

Comprehensive analysis of acetylcholinesterase inhibitor and reactivator complexes: implications for drug design and antidote development

The main function of acetylcholinesterase (AChE) is to regulate the levels of one of the most important neurotransmitters: acetylcholine. This makes AChE an ideal molecular target for the treatment of neurodegenerative diseases and dementia (such as Alzheimer's disease), as well as for the neutralisation of natural toxins (e.g., venom peptides) and chemical warfare agents. The significance of AChE inhibitors in slowing the progression of dementia, as well as the role of reactivators in treating poisoned individuals, is reflected in several co-crystallised complexes deposited in the Protein Data Bank. In this study, we analysed all deposited AChE-small-molecule complexes to gain insights into compound binding and to provide guidance for the future design of therapeutic drugs and new antidotes.

N-Benzyl piperidine Fragment in Drug Discovery

The N-benzyl piperidine (N-BP) structural motif is commonly employed in drug discovery due to its structural flexibility and three-dimensional nature. Medicinal chemists frequently utilize the N-BP motif as a versatile tool to fine-tune both efficacy and physicochemical properties in drug development. It provides crucial cation-π interactions with the target protein and also serves as a platform for optimizing stereochemical aspects of potency and toxicity. This motif is found in numerous approved drugs and clinical/preclinical candidates. This review focuses on the applications of the N-BP motif in drug discovery campaigns, emphasizing its role in imparting medicinally relevant properties. The review also provides an overview of approved drugs, the clinical and preclinical pipeline, and discusses its utility for specific therapeutic targets and indications, along with potential challenges.

Searching for potential acetylcholinesterase inhibitors: a combined approach of multi-step similarity search, machine learning and molecular dynamics simulations

Targeting acetylcholinesterase is one of the most important strategies for developing therapeutics against Alzheimer's disease. In this work, we have employed a new approach that combines machine learning models, a multi-step similarity search of the PubChem library and molecular dynamics simulations to investigate potential inhibitors for acetylcholinesterase. Our search strategy has been shown to significantly enrich the set of compounds with strong predicted binding affinity to acetylcholinesterase. Both machine learning prediction and binding free energy calculation, based on linear interaction energy, suggest that the compound CID54414454 would bind strongly to acetylcholinesterase and hence is a promising inhibitor.

Efficient, rapid, and high-yield synthesis of aryl Schiff base derivatives and their in vitro and in silico inhibition studies of hCA I, hCA II, AChE, and BuChE

This study reports a rapid and efficient synthesis of four novel aryl Schiff base derivatives. Biological activity and molecular modeling studies were conducted to evaluate the inhibitory effects of these compounds on human carbonic anhydrases (hCA) and cholinesterases. The results indicate that the triazole-ring-containing compounds have strong inhibitory effects on hCA I, hCA II, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) targets. Besides comparing the Schiff bases synthesized in our study to reference molecules, we conducted in silico investigations to examine how these compounds interact with their targets. Our studies revealed that these compounds can occupy binding sites and establish interactions with crucial residues, thus inhibiting the functions of the targets. These findings have significant implications as they can be utilized to develop more potent compounds for treating the diseases that these target proteins play crucial roles in or to obtain drug precursors with enhanced efficacy.

Design, synthesis, and biological evaluation of 1,2,4-oxadiazole-based derivatives as multitarget anti-Alzheimer agents

A series of novel 1,2,4-oxadiazole-based derivatives were synthesized and evaluated for their potential anti-Alzheimer disease activity. The results revealed that compounds 2b, 2c, 2d, 3a, 4a, 6, 9a, 9b, and 13b showed excellent inhibitory activity against acetylcholinesterase (AChE) with IC50 values in the range of 0.0158 to 0.121 μM. They were 1.01 to 7.78 times more potent than donepezil (IC50 = 0.123 μM). The newly synthesized compounds exhibited lower activity towards butyrylcholinesterase (BuChE) when compared to rivastigmine. Compounds 4b and 13b showed the most prominent inhibitory potential against BuChE with IC50 values of 11.50 and 15 μM, respectively. Moreover, 4b, and 9b were found to be more potent antioxidant agents (IC50 values of 59.25, and 56.69 μM, respectively) in comparison with ascorbic acid (IC50 = 74.55 μM). Compounds 2b and 2c exhibited monoamine oxidase-B (MAO-B) inhibitory activity with IC50 values of 74.68 and 225.48 μM, respectively. They were 3.55 and 1.17 times more potent than biperiden (IC50 = 265.85 μM). The prominent interactions of the compounds with the AChE active site can be used to computationally explain the high AChE inhibitory activity. The results unveiled 1,2,4-oxadiazole derivatives 2c and 3a as multitarget anti-AD agents. The predicted ADME properties for compounds 2b and 4a were satisfactory, and 4a had the highest likelihood of crossing the blood-brain barrier (BBB), making it the optimum compound for future optimization.

In silico analysis of the use of solanine derivatives as a treatment for Alzheimer's disease

Alzheimer's disease (AD) is a brain illness that causes cognitive impairment in the elderly, especially females, as a result of genetics, hormones, and life experiences. It becomes more severe with age and is associated with cardiovascular disease, hypertension, and diabetes. Beta-amyloid plaques and hyper phosphorylated Tau protein buildup are common clinical findings. Misfiling of amyloid precursor protein (APP) and Amyloid beta peptide (Aβ) proteins contributes to Alzheimer's disease. Enzyme Acetylcholinesterase enzyme interacts with amyloid-beta, enhancing its accumulation in insoluble plaques, leading to successful treatment for Alzheimer's disease primarily based on lowering this enzyme. Treatments include using the Rivastigmine for mild, moderate, or severe Alzheimer's disease, which inhibits acetylcholinesterase, but may cause side effects; Solanine derivatives, nightshade toxin, it is cholinesterase inhibitory, may mitigate Alzheimer's illness is progressing. In this research utilized a molecular docking program, which is a computer's computational ability to determine the optimal position for a specific compound to bind to a protein or target, forming a target-ligand complex and displaying biological activity and aiding in the development of effective anti-AD treatments and understanding AD pathological mechanisms. The study examined complexes of 3LII (Acetylcholinesterase receptor) in the A and B chain with Solanine and Rivastigmine derivatives, using an in-silico approach. PyRx default sorter was used to improve docking accuracy. Four compounds were selected based on their higher binding affinities in chain A and B. The results showed that Solanine derivatives (alpha-Solanine, Beta1-Solanine and Beta2-Solanine) have higher binding strength (-9.0,-9.3 and -8.6) than Rivastigmine (-7.2) in chain A, and also the binding strength was high for the Solanine derivatives (alpha-Solanine, Beta1-Solanine, and Beta2-Solanine) (-9.0,-8.8 and -8.9) is higher than Rivastigmine (-6.0) in the chain B. Solanine derivatives showed higher binding strength with acetylcholinesterase, potentially for to reduce the progression of the disease.

A theoretical screening of phytochemical constituents from Millettia brandisiana as inhibitors against acetylcholinesterase

Alzheimer's disease is one of the causes associated with the early stages of dementia. Nowadays, the main treatment available is to inhibit the actions of the acetylcholinesterase (AChE) enzyme, which has been identified as responsible for the disease. In this study, computational methods were used to examine the structure and therapeutic ability of chemical compounds extracted from Millettia brandisiana natural products against AChE. This plant is commonly known as a traditional medicine in Vietnam and Thailand for the treatment of several diseases. Furthermore, machine learning helped us narrow down the choice of 85 substances for further studies by molecular docking and molecular dynamics simulations to gain deeper insights into the interactions between inhibitors and disease proteins. Of the five top-choice substances, γ-dimethylallyloxy-5,7,2,5-tetramethoxyisoflavone emerges as a promising substance due to its large free binding energy to AChE and the high thermodynamic stability of the resulting complex.

Novel benzene sulfonamides with acetylcholinesterase and carbonic anhydrase inhibitory actions

A series of benzene sulfonamides 15-26 were synthesized and determined for their in vitro and in silico inhibitory profiles toward acetylcholinesterase (AChE) and carbonic anhydrases (CAs). Commercially available 3,4-dimethoxytoluene was reacted with chlorosulfonic acid to furnish benzene sulfonyl chloride derivatives. The reaction of substituted benzene sulfonyl chloride with some amines also including (±)-α-amino acid methyl esters afforded a series of novel benzene sulfonamides. In this study, the enzyme inhibition abilities of these compounds were evaluated against AChE and CAs. They exhibited a highly potent inhibition ability on AChE and -CAs (Ki values are in the range of 28.11 ± 4.55 nM and 145.52 ± 28.68 nM for AChE, 39.20 ± 2.10 nM to 131.54 ± 12.82 nM for CA I, and 50.96 ± 9.83 nM and 147.94 ± 18.75 nM for CA II). The present newly synthesized novel benzene sulfonamides displayed efficient inhibitory profiles against AChE and CAs, and it is anticipated that they may emerge as lead molecules for some diseases including glaucoma, epilepsy, and Alzheimer's disease.

Acetylcholinesterase inhibitory activities of some flavonoids from the root bark of Pinus krempfii Lecomte: in vitro and in silico study

From the root bark of Pinus krempfii Lecomte, four flavonoids were isolated and evaluated for their inhibitory activities against AChE and BChE enzymes in vitro and in silico. Tectochrysin (1) was found to inhibit AChE with an IC50 value of 33.69 ± 2.80 μM. The docking study results also showed agreement with the in vitro test results. All four compounds also showed the best binding affinity for the AChE enzyme, characterised by binding energy (ΔG) values as low as -8.1 to -9.3 kcal/mol, in which, the compound tectochrysin had the best binding affinity for the AChE protein with a ΔG value of -9.329 kcal/mol. Tectochrysin (1) was also bound to the amino acid Phe295 of AChE with a bond length of 2.8 Å, similar to the control dihydrotanshinone-I. Galangin (2) also showed its in vitro inhibitory activity against BChE with an IC50 value of 82.21 ± 2.70 μM. In silico, it also had the best binding energy value of -9.072 kcal/mol with BChE and formed hydrogen bonds with the His438 (2.85 Å) residues of BChE like the positive control (tacrine). The steered molecular dynamics (SMD) simulation results of these two complexes revealed a mechanistic insight that the protein-ligand complexes showed stable trajectories throughout the 20 and 150 ns simulations. Moreover, the drug likeliness suggested that both flavonoids (1 and 2) were expected to be drug-like and have an LD50 toxicity level of 5. This study has contributed new results for drug discovery and the development of substances with neuroprotective effects, especially for the treatment of Alzheimer's disease.Communicated by Ramaswamy H. Sarma.

Virtual Screening of Molecules via Neural Fingerprint-based Deep Learning Technique

A machine learning-based drug screening technique has been developed and optimized using convolutional neural network-derived fingerprints. The optimization of weights in the neural network-based fingerprinting technique was compared with fixed Morgan fingerprints in regard to binary classification on drug-target binding affinity. The assessment was carried out using six different target proteins using randomly chosen small molecules from the ZINC15 database for training. This new architecture proved to be more efficient in screening molecules that less favorably bind to specific targets and retaining molecules that favorably bind to it.

Scientific contribution

We have developed a new neural fingerprint-based screening model that has a significant ability to capture hits. Despite using a smaller dataset, this model is capable of mapping chemical space similar to other contemporary algorithms designed for molecular screening. The novelty of the present algorithm lies in the speed with which the models are trained and tuned before testing its predictive capabilities and hence is a significant step forward in the field of machine learning-embedded computational drug discovery.

The pharmacological properties of Gypsophila eriocalyx: The endemic medicinal plant of northern central Turkey

The aim of this study is to evaluate and compare the biological properties of different extracts (methanol, ethanol, and water) obtained from Gypsophila eriocalyx (G. eriocalyx), a medicinal plant traditionally used in Turkey. The components of different extracts were defined using the GC-MS method. The effects of G. eriocalyx extracts on cell proliferation, apoptosis, and cell cycle arrest in MDA-MB-231 breast cancer as well as in vitro antioxidant, enzyme inhibition, and antimicrobial activities were investigated. In accordance with the results obtained, although ethanol and methanol extracts of G. eriocalyx show higher antioxidant activity than G. eriocalyx water extract, enzyme inhibition activities of the extracts were not found to be significant compared to the reference drug. The methanol and ethanol extract of G. eriocalyx exhibited moderate antimicrobial activity against Staphylococcus aureus and methanol extract showed significant antimicrobial activity against Bacillus cereus. In addition, both extracts significantly inhibited cell viability in a dose-dependent manner in breast cancer cells. The cell growth inhibition by methanol and ethanol extracts induced S phase cell-cycle arrest and apoptosis in MDA-MB-231 cells. Lastly, in order to compare the activities of the chemicals found in Gypsophila eriocalyx plant extract, their activities against various proteins that are breast cancer protein (PDB ID:1A52 and 1JNX), antioxidant protein (PDB ID: 1HD2), AChE enzyme protein (PDB ID: 4M0E), BChE enzyme protein (PDB ID: 5NN0), and Escherichia coli protein (PDB ID: 4PRV)were compared. Then, ADME/T analysis calculations were made to examine the effects of molecules with high activity on human metabolism. Eventually, G. eriocalyx is thought to be a potent therapeutic herb that can be considered as an alternative and functional therapy for the management of diseases of a progressive nature related to oxidative damage such as infection, diabetes, cancer, and Alzheimer's disease.

Development of novel 9H-carbazole-4H-chromene hybrids as dual cholinesterase inhibitors for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease affecting mental ability and neurocognitive functions. Cholinesterase enzymes affect concentration of acetylcholine in the brain, leading to dementia. Thus, there is an urgent need to develop novel dual cholinesterase inhibitors as possible anti-AD drugs. Herein, we have designed and synthesized a novel series of 9H-carbazole-4H-chromenes 4(a-l) through a one-pot three-component reaction of salicylaldehydes (1), hydroxycarbazole (2) and N-methyl-1-(methylthio)-2-nitroethenamine (3) using triethylamine as a catalyst in ethanol. Synthetic transformation involves the formation of two C-C bonds and one C-O bond in a single step to obtain desired analogs. The rapid one-pot reaction does not require chromatographic purification, proceeds under mild conditions, and exhibits good tolerance toward various functional groups with high synthetic yields. Synthesized compounds were screened for cytotoxicity using MTT assay in BV-2 microglial cells. These compounds were then in-vitro screened against acetylcholinesterase (AChE) and butyrylcholinestrase (BuChE) enzymes. Most of these ligands have shown dual cholinesterase inhibitory activity compared to the standard drug. In-vitro results showed that the compounds 4a and 4d have promising anticholinesterase response against both cholinesterase enzymes (4a, AChE IC50: 5.76 µM, BuChE IC50: 48.98 µM; 4d, AChE IC50: 3.58 µM, BuChE IC50: 42.73 µM). In-vitro results were validated by molecular docking and dynamic simulation at 100 ns. Molecular docking and molecular dynamics simulation study strongly supported structural features present in these analogs. Together, these analogs could be exploited to develop dual anti-cholinesterase candidates to treat AD in combination with other drugs.

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

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

Design, synthesis, in silico, and in vitro evaluation of novel benzyloxybenzene substituted (S)-α-amino amide derivatives as cholinesterases and monoaminoxidases inhibitor

In this study, a series of novel benzyloxybenzene substituted (S)-α-amino acid methyl esters and their amide derivatives were synthesized and evaluated for their inhibitory actions against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase A (MAO-A), and monoamine oxidase B (MAO-B). The synthetic strategy was based on starting from benzyl bromide (5) and 4-hydroxybenzaldehyde (6). The reaction of 5 and 6 in the presence of K2 CO3 gave benzyloxybenzaldehyde 7. Benzyloxybenzene substituted (S)-α-amino acid methyl esters 11, 12, 13, (±)-19, and (±)-20 were obtained from the reaction of  L-amino acid methyl esters with benzyloxybenzaldehyde (7) followed by in situ reduction with NaBH4 . The reaction of (S)-11, (S)-12, 13, (±)-19, and (±)-20 with excess ammonia gave amides (S)-14, (S)-15, 16, (±)-21, and (±)-22. The in vitro inhibitory activities of compounds against MAO-A, MAO-B, AChE, and BChE were investigated. Within the α-amino acid methyl ester series, 13 (21.32 ± 0.338 µM) showed selectivity by inhibiting the MAO-B better than MAO-A. 13 emerged as the most active member of this series, exhibiting a 12-fold selectivity for MAO-B. 14 (4.501 ± 0.295 µM) demonstrated a pronounced selectivity for MAO-A over MAO-B, with a selectivity ratio of 110-fold. In addition, it was determined that compound 15 (95.65 ± 3.09 µM) had high selectivity for BChE inhibition. 21 was demonstrated the most potent inhibition (18.36 ± 1.36 µM) against AChE.

ADME profiling, molecular docking, DFT, and MEP analysis reveal cissamaline, cissamanine, and cissamdine from Cissampelos capensis L.f. as potential anti-Alzheimer's agents

The current pharmacotherapies for Alzheimer's disease (AD) demonstrate limited efficacy and are associated with various side effects, highlighting the need for novel therapeutic agents. Natural products, particularly from medicinal plants, have emerged as a significant source of potential neuroprotective compounds. In this context, Cissampelos capensis L.f., renowned for its medicinal properties, has recently yielded three new proaporphine alkaloids; cissamaline, cissamanine, and cissamdine. Despite their promising bioactive profiles, the biological targets of these alkaloids in the context of AD have remained unexplored. This study undertakes a comprehensive in silico examination of the binding affinity and molecular interactions of these alkaloids with human protein targets implicated in AD. The drug likeness and ADME analyses indicate favorable pharmacokinetic profiles for these compounds, suggesting their potential efficacy in targeting the central nervous system. Molecular docking studies indicate that cissamaline, cissamanine, and cissamdine interact with key AD-associated proteins. These interactions are comparable to, or in some aspects slightly less potent than, those observed with established AD drugs, highlighting their potential as novel therapeutic agents for Alzheimer's disease. Crucially, Density Functional Theory (DFT) calculations offer deep insights into the electronic and energetic characteristics of these alkaloids. These calculations reveal distinct electronic properties, with differences in total energy, binding energy, HOMO-LUMO gaps, dipole moments, and electrophilicity indices. Such variations suggest unique reactivity profiles and molecular stability, pertinent to their pharmacological potential. Moreover, Molecular Electrostatic Potential (MEP) analyses provide visual representations of the electrostatic characteristics of these alkaloids. The analyses highlight areas prone to electrophilic and nucleophilic attacks, indicating their potential for specific biochemical interactions. This combination of DFT and MEP results elucidates the intricate electronic, energetic, and electrostatic properties of these compounds, underpinning their promise as AD therapeutic agents. The in silico findings of this study shed light on the promising potential of cissamaline, cissamanine, and cissamdine as agents for AD treatment. However, further in vitro and in vivo studies are necessary to validate these theoretical predictions and to understand the precise mechanisms through which these alkaloids may exert their therapeutic effects.

Identification of a novel drug molecule for neurodegenerative disease from marine algae through in-silico analysis

Cognitive functions are lost due to the rapid hydrolysis of acetylcholine including Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE). Marine algae-derived compounds were reported for their neuroprotective activities and hence they can be utilised for treating neurodegenerative ailments like Alzheimer's Disease and Parkinson's Disease which are due to the loss of cognitive functions. Major attention is currently paid to seaweeds due to their health benefits and high nutritional values. Sea weeds are of a rich sense of natural bioactive compounds which antioxidants, pharmaceutical compounds, flavonoids and alkaloids. They also contain a high amount of vitamins A, D, E, C and Ca, K, Mg and Fe. Regular consumption of a marine algae-based diet may boost immunities. In searching for natural cholinesterase inhibitors, the present study is focussed on some marine bioactive compounds reported from brown, red and green algae. Molecular docking studies have been carried out along with molecular dynamics simulations studies and binding energy calculations resulting in three best bioactive compounds when AChE is used as the target. The results are compared with cocrystal studies. Two best compounds, namely, Diphlorethohydroxycarmalol and Phlorofucofuroeckol from the brown seaweeds are identified as the potential lead compounds for neurodegenerative diseases, Alzheimer's and Parkinson's.Communicated by Ramaswamy H. Sarma.

Design, synthesis and anticholinergic properties of novel α-benzyl dopamine, tyramine, and phenethylamine derivatives

Due to the important biological properties of dopamine, phenethylamine, and tyramine derivatives in the central nervous system, herein the synthesis of novel α-benzyl dopamine, phenethylamine, and tyramine derivatives is described. The title compounds were synthesized starting from 3-phenylpropanoic acids and methoxybenzenes in six or seven steps. Firstly, 3-(2,3-dimethoxyphenyl)propanoic acid (11) and 3-(3,4-dimethoxyphenyl)propanoic acid (12) were selectively brominated with N-bromosuccinimide (NBS). The Friedel-Crafts acylation of methoxylated benzenes with these brominated acids or commercially available 3-phenylpropanoic acid in polyphosphoric acid gave the desired dihydrochalcones. α-Carboxylation of dihydrochalcones, reduction of benzylic carbonyl groups, hydrolysis of esters to acid derivatives, and the Curtius rearrangement reaction of acids followed by in situ synthesis of carbamates from alkyl isocyanates and hydrogenolysis of the carbamates afforded the title compounds in good total yields. Alzheimer's disease (AD) and Parkinson's disease (PD) are chronic neurodegenerative diseases that become serious over time. However, the exact pathophysiology of both diseases has not been revealed yet. There have been many different approaches to the treatment of patients for many years, especially studies on the cholinergic system cover a wide area. Within the scope of this study, the inhibition effects of dopamine-derived carbamates and amine salts on the cholinergic enzymes AChE and BChE were examined. Dopamine-derived carbamate 24a-i showed inhibition in the micro-nanomolar range; compound 24d showed a Ki value of 26.79 nM against AChE and 3.33 nM against BChE, while another molecule, 24i, showed a Ki range of 27.24 nM and 0.92 nM against AChE and BChE, respectively. AChE and BChE were effectively inhibited by dopamine-derived amine salts 25j-s, with Ki values in the range of 17.70 to 468.57 µM and 0.76-211.23 µM, respectively. Additionally, 24c, 24e and 25m were determined to be 60, 276 and 90 times more selective against BChE than AChE, respectively.

3D-QSAR-based pharmacophore modelling of quinazoline derivatives for the identification of acetylcholinesterase inhibitors through virtual screening, molecular docking, molecular dynamics and DFT studies

Alzheimer's disease (AD) is a progressive neurological disorder responsible for the cognitive dysfunction and cognitive impairment in the patients. Acetylcholinesterase inhibitors (AChEIs) are used to treat AD however, these only provided symptomatic relief and more efficient drug molecules are desired for the effective treatment of the disease. In this article, ligand-based drug-designing strategy was used to develop and validate a field-based 3D-QSAR pharmacophore model on quinazoline-based AChEIs reported in the literature. The validated pharmacophore model (AAAHR_1) was used as a prefilter to screen an ASINEX database via virtual screening workflow (VSW). The hits generated were subjected to MM-GBSA to identify potential AChEIs and top three scoring molecules (BAS 05264565, LEG 12727144 and SYN 22339886) were evaluated for thermodynamic stability at the target site using molecular dynamic simulations. Additionally, DFT study was performed to predict the reactivity of lead molecules towards acetylcholinesterase (AChE). Thus, by utilising various computational tools, three molecules were identified as potent AChEIs that can be developed as potential drug candidates for the treatment of AD.Communicated by Ramaswamy H. Sarma.

A biochemistry-oriented drug design: synthesis, anticancer activity, enzymes inhibition, molecular docking studies of novel 1,2,4-triazole derivatives

In this study, we researched the reactions of 5-(5-bromofuran-2-yl)-4-methyl-1,2,4-triazole-3-thiol and 5-thiophene-(3-ylmethyl)-4R-1,2,4-triazole-3-thiols with some halogen-containing compounds, a number of new compounds were synthesized (1.1-1.5 and 2.1-2.8). These compounds showed excellent to good inhibitory activities on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. For obtaining the effects of these compounds on AChE and BChE enzymes were determined spectrophotometrically according to Ellman. IC50 values of these enzymes were ranging between 1.63 and 17.68 nM for AChE and 8.71 and 84.02 nM for BChE. After, prostate cancer is the second leading cause of cancer-related mortality for men over the age of 65 in developed countries. Current treatment options remain limited in the treatment of advanced-stage prostate cancer leading to biochemical recurrence in almost 40% of the patients. Therefore, there is an urgent need for development of novel therapeutic tools for treatment of prostate cancer patients. In this study, we aimed at analyzing the potential of all compounds against prostate cancer cells. We found that, of the tested compounds, 2.1, 2.2 and 2.3 showed significant cytotoxic activities against PC3 prostate cancer cells, although their effect on the viability of normal prostate cells was limited. These findings suggest their selective targeting potential for prostate cancer cells and offer them as candidate therapeutic agents against prostate cancer. The inhibitory activities of some chemical compounds, such as (1.1-1.5 and 2.1-2.8) were assessed by performing the molecular docking study in the presence of AChE, BChE and prostate cancer protein. MM/GBSA methods are calculated binding free energy. Finally, ADME/T analysis was performed to examine the drug properties of the 13 studied molecules.Communicated by Ramaswamy H. Sarma.

Noncovalent binding of carbofuran to acetylcholinesterase from Homo sapiens, Danio rerio, Apis mellifera and Caenorhabditis elegans: Homology modelling, molecular docking and dynamics, and quantum biochemistry description

Although various regulatory agencies have banned or severely restricted the use of carbofuran (CAR), recent reports indicate the presence of CAR residues in both cultivated and wild areas. This pesticide is a potent inhibitor of acetylcholinesterase (AChE), which acts by preventing the hydrolysis of acetylcholine (ACh). Given the critical role of AChE::ACh in the proper functioning of the nervous system, we thought it appropriate to investigate the binding of CAR to AChEs from Homo sapiens, Danio rerio, Apis mellifera, and Caenorhabditis elegans using homology modelling, molecular docking, molecular dynamics, and quantum biochemistry. Molecular docking and dynamics results indicated peculiar structural behavior in each AChE::CAR system. Quantum biochemistry results showed similar affinities for all complexes, confirming the description of carbofuran as a broad-spectrum pesticide, and have a limited correlation with IC50 values. We found the following decreasing affinity order of AChE species: H. sapiens > A. mellifera > C. elegans > D. rerio. The computational results suggest that CAR occupies different pockets in the AChEs studied. In addition, our results showed that CAR binds to hsAChE and ceAChE in a very similar manner: it has high affinities for the same subsites in both species and forms hydrogen bonds with residues (hsTYR124 and ceTRP107) occupying homologous positions in the peripheral site. This suggests that this nematode is a potential model to evaluate the toxicity of carbamates, even though the sequence identity between them is only 41 %. Interestingly, we also observed that the catalytic histidines of drAChE and amAChE exhibited favorable contacts with carbofuran, suggesting that the non-covalent binding of carbofuran to these proteins may promote faster carbamylation rates than the binding modes to human and worm acetylcholinesterases. Our computational results provide a better understanding of the binding mechanisms in these complexes, as well as new insights into the mechanism of carbamylation.

Bi(OTf)3-promoted cascade annulation of hydroxy-pyranones and unsaturated γ-ketoesters for the construction of polycyclic bridged pyrano-furopyranones

An efficient protocol for constructing complex three dimensional polycyclic bridged chromano-furopyranones and pyrano-furopyranones (closely related to bioactive natural products) via bismuth(III)-catalyzed cascade annulation of hydroxy-pyranones and unsaturated γ-ketoesters is presented. This process involves intermolecular Michael addition, intramolecular hemiketalization, lactonization, formation of one C-C bond and two C-O bonds, rings, and contiguous stereocenters.

Novichok Nerve Agents as Inhibitors of Acetylcholinesterase-In Silico Study of Their Non-Covalent Binding Affinity

In silico studies were performed to assess the binding affinity of selected organophosphorus compounds toward the acetylcholinesterase enzyme (AChE). Quantum mechanical calculations, molecular docking, and molecular dynamics (MD) with molecular mechanics Generalized-Born surface area (MM/GBSA) were applied to assess quantitatively differences between the binding energies of acetylcholine (ACh; the natural agonist of AChE) and neurotoxic, synthetic correlatives (so-called "Novichoks", and selected compounds from the G- and V-series). Several additional quantitative descriptors like root-mean-square fluctuation (RMSF) and the solvent accessible surface area (SASA) were briefly discussed to give-to the best of our knowledge-the first quantitative in silico description of AChE-Novichok non-covalent binding process and thus facilitate the search for an efficient and effective treatment for Novichok intoxication and in a broader sense-intoxication with other warfare nerve agents as well.

Rearranged Homoadamantane-Type Polycyclic Polyprenylated Acylphloroglucinols from Hypericum pseudohenryi

Hypseudohenones A-C (1-3), the first rearranged homoadamantane-type polycyclic polyprenylated acylphloroglucinols, were isolated from Hypericum pseudohenryi. Their structures with an unprecedented tricyclo[4.3.1.13,8]undecane-2,4,10-trione core were determined by spectroscopic analysis, quantum-chemical calculations, and X-ray crystallography. A method for determining the relative configuration at C-3 was established by the peak shape of H-28 or J-value of H-3/H-28. Moreover, 2-3 exhibited significant AChE inhibitory activity, and the interactions of 2-3 with AChE were evaluated by molecular docking.

Ginkgo biloba: Antioxidant Activity and In Silico Central Nervous System Potential

Ginkgo biloba (GB) extracts have been used in clinical studies as an alternative therapy for Alzheimer's disease (AD), but the exact bioaction mechanism has not yet been elucidated. In this work, an in silico study on GB metabolites was carried out using SwissTargetPrediction to determine the proteins associated with AD. The resulting proteins, AChE, MAO-A, MAO-B, β-secretase and γ-secretase, were studied by molecular docking, resulting in the finding that kaempferol, quercetin, and luteolin have multitarget potential against AD. These compounds also exhibit antioxidant activity towards reactive oxygen species (ROS), so antioxidant tests were performed on the extracts using the DPPH and ABTS techniques. The ethanol and ethyl acetate GB extracts showed an important inhibition percentage, higher than 80%, at a dose of 0.01 mg/mL. The effect of GB extracts on AD resulted in multitarget action through two pathways: firstly, inhibiting enzymes responsible for degrading neurotransmitters and forming amyloid plaques; secondly, decreasing ROS in the central nervous system (CNS), reducing its deterioration, and promoting the formation of amyloid plaques. The results of this work demonstrate the great potential of GB as a medicinal plant.

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.

Development of Potential Multi-Target Inhibitors for Human Cholinesterases and Beta-Secretase 1: A Computational Approach

Alzheimer's disease causes chronic neurodegeneration and is the leading cause of dementia in the world. The causes of this disease are not fully understood but seem to involve two essential cerebral pathways: cholinergic and amyloid. The simultaneous inhibition of AChE, BuChE, and BACE-1, essential enzymes involved in those pathways, is a promising therapeutic approach to treat the symptoms and, hopefully, also halt the disease progression. This study sought to identify triple enzymatic inhibitors based on stereo-electronic requirements deduced from molecular modeling of AChE, BuChE, and BACE-1 active sites. A pharmacophore model was built, displaying four hydrophobic centers, three hydrogen bond acceptors, and one positively charged nitrogen, and used to prioritize molecules found in virtual libraries. Compounds showing adequate overlapping rates with the pharmacophore were subjected to molecular docking against the three enzymes and those with an adequate docking score (n = 12) were evaluated for physicochemical and toxicological parameters and commercial availability. The structure exhibiting the greatest inhibitory potential against all three enzymes was subjected to molecular dynamics simulations (100 ns) to assess the stability of the inhibitor-enzyme systems. The results of this in silico approach indicate ZINC1733 can be a potential multi-target inhibitor of AChE, BuChE, and BACE-1, and future enzymatic assays are planned to validate those results.

Identification of Potential Multitarget Compounds against Alzheimer's Disease through Pharmacophore-Based Virtual Screening

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive loss of cognitive functions, and it is the most prevalent type of dementia worldwide, accounting for 60 to 70% of cases. The pathogenesis of AD seems to involve three main factors: deficiency in cholinergic transmission, formation of extracellular deposits of β-amyloid peptide, and accumulation of deposits of a phosphorylated form of the TAU protein. The currently available drugs are prescribed for symptomatic treatment and present adverse effects such as hepatotoxicity, hypertension, and weight loss. There is urgency in finding new drugs capable of preventing the progress of the disease, controlling the symptoms, and increasing the survival of patients with AD. This study aims to present new multipurpose compounds capable of simultaneously inhibiting acetylcholinesterase (AChE), butyrylcholinesterase (BChE)-responsible for recycling acetylcholine in the synaptic cleft-and beta-secretase 1 (BACE-1)-responsible for the generation of amyloid-β plaques. AChE, BChE, and BACE-1 are currently considered the best targets for the treatment of patients with AD. Virtual hierarchical screening based on a pharmacophoric model for BACE-1 inhibitors and a dual pharmacophoric model for AChE and BChE inhibitors were used to filter 214,446 molecules by QFITBACE > 0 and QFITDUAL > 56.34. The molecules selected in this first round were subjected to molecular docking studies with the three targets and further evaluated for their physicochemical and toxicological properties. Three structures: ZINC45068352, ZINC03873986, and ZINC71787288 were selected as good fits for the pharmacophore models, with ZINC03873986 being ultimately prioritized for validation through activity testing and synthesis of derivatives for SAR studies.

An exploration of the binding prediction of anatoxin-a and atropine to acetylcholinesterase enzyme using multi-level computer simulations

Acetylcholinesterase (AChE) is crucial for the breakdown of acetylcholine to acetate and choline, while the inhibition of AChE by anatoxin-a (ATX-a) results in severe health complications. This study explores the structural characteristics of ATX-a and its interactions with AChE, comparing to the reference molecule atropine for binding mechanisms. Molecular docking simulations reveal strong binding affinity of both ATX-a and atropine to AChE, interacting effectively with specific amino acids in the binding site as potential inhibitors. Quantitative assessment using the MM-PBSA method demonstrates a significantly negative binding free energy of -81.659 kJ mol-1for ATX-a, indicating robust binding, while atropine exhibits a stronger binding affinity with a free energy of -127.565 kJ mol-1. Umbrella sampling calculates the ΔGbindvalues to evaluate binding free energies, showing a favorable ΔGbindof -36.432 kJ mol-1for ATX-a and a slightly lower value of -30.12 kJ mol-1for atropine. This study reveals the dual functionality of ATX-a, acting as both a nicotinic acetylcholine receptor agonist and an AChE inhibitor. Remarkably, stable complexes form between ATX-a and atropine with AChE at its active site, exhibiting remarkable binding free energies. These findings provide valuable insights into the potential use of ATX-a and atropine as promising candidates for modulating AChE activity.

Design, syntheses, theoretical calculations, MM-GBSA, potential anti-cancer and enzyme activities of novel Schiff base compounds

In this study, new Schiff base compounds (SB-F-OH, SB-Cl-OH and SB-Br-OH) were derived from chalcone-derived amine compounds containing halogen groups and 4-hydroxybenzaldehyde. Also, their phthalonitrile compounds (SB-F-CN, SB-Cl-CN and SB-Br-CN) have been synthesized. The structures of these compounds were elucidated by NMR, FT-IR and Mass spectroscopic methods. The quantum chemical parameters were calculated at B3LYP/6-31++g(d,p), HF/6-31++g(d,p) and M062X/6-31++g(d,p) levels. As the biological application of the synthesized compounds, (i) their inhibition properties of the synthesized compounds on Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE) metabolic enzymes were investigated, and their potential anticancer activities against neuroblastoma (NB; SH-SY5Y) and healthy fibroblast (NIH-3T3) cell lines were determined by in vitro assays. All compounds showed inhibition at nanomolar level with the Ki values in the range of 97.86 ± 30.51-516.82 ± 31.42 nM for AChE, 33.21 ± 4.45-78.50 ± 8.91 nM for BChE, respectively. It has been determined that all tested compounds have a remarkable cytotoxic effect against SH-SY5Y, and IC50 values were significantly lower than NIH-3T3 cells. The lowest IC50 value was observed in SB-Cl-OH (7.48 ± 0.86 µM) and SB-Cl-CN (7.31 ± 0.69 µM). The molecular docking of the molecules was also investigated using crystal structure of AChE enzyme protein (PDB ID: 4M0E), crystal structure of BChE protein (PDB ID: 6R6V) and SH-SY5Y cancer protein (PDB ID: 2F3F, 3PBL and 5WIV). The ADME properties of the compounds were investigated. MM/GBSA method is calculated binding free energy. Afterwards, ADME/T analysis was performed to examine the some properties of the molecules.Communicated by Ramaswamy H. Sarma.

Screening of Multitarget-Directed Natural Compounds as Drug Candidates for Alzheimer's Disease Using In Silico Techniques: Their Extraction and In Vitro Validation

Alzheimer's disease (AD) is a neurodegenerative disorder that impairs neurocognitive function. Acetylcholinesterase (AChE) and β-site APP cleaving enzyme 1 (BACE1) are the two main proteins implicated in AD. Indeed, the major available commercial drugs (donepezil, rivastigmine, and galantamine) against Alzheimer's are AChE inhibitors. However, none of these drugs are known to reverse or reduce the pathophysiological condition of the disease since there are multiple contributing factors to AD. Therefore, there is a need to develop a multitarget-directed ligand approach for its treatment. In the present study, plant bioactive compounds were screened for their AChE and BACE1 inhibition potential by conducting molecular docking studies. Considering their docking score and pharmacokinetic properties, limonin, peimisine, serratanine B, and withanolide A were selected as the lead compounds. Molecular dynamics simulations of these protein-ligand complexes confirmed the conformational and energetically stabilized enzyme-inhibitor complexes. The inhibition potential of the lead compounds was validated by in vitro enzyme assay. Withanolide A inhibited AChE (IC50 value of 107 μM) and showed mixed-type inhibition. At this concentration, it inhibited BACE1 activity by 57.10% and was stated as most effective. Both the compounds, as well as their crude extracts, were found to have no cytotoxic effect on the SH-SY5Y cell line.

Novel alkyl-substituted 4-methoxy benzaldehyde thiosemicarbazones: Multi-target directed ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder affecting mental ability and interrupts neurocognitive functions. Treating multifactorial conditions of AD with a single-target-directed drug is highly difficult. Thus, a multi-target-directed ligand (MTDL) development strategy has been developed as a promising approach for the treatment of AD. Herein, we have synthesized two novel thiosemicarbazones as MTDLs and reported their bioactivities against diverse neuropathological events involved in AD. In vitro studies revealed that both compounds exhibited promising anticholinesterase activity (AChE, IC50 = 15.98 μM, MZET and IC50 = 30.23 μM, MZMT), well supported by a detailed computational study. Both analogs have shown good thermodynamic behaviour and stability through interactions with characteristic amino acid residues throughout simulation of 100 ns against acetylcholinesterase enzyme. In an electrophysiology assay, these analogs have shown a characteristic inhibitory response against the GluN1-1a + GluN2B subunit of N-methyl-D-aspartate receptors. Pre-treatment of BV-2 microglial cells with MZET effectively decreased nitrite production compared to nitrite produced by lipopolysaccharide-treated cells alone. Further, the effect of MZMT and MZET on autophagy regulation was determined using stably transfected SH-SY5Y neuroblastoma cells. MZET significantly enhanced the autophagy flux in neuroblastoma cells. A significant decrease in copper-catalysed oxidation of amyloid-β in presence of synthesized thiosemicarbazones was also observed. Collectively, our findings indicated that these analogs have potential as effective anti-AD candidates and can be used as a prototype to develop more safer multi-targeted anti-AD drugs.

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.

A safe alternative synthesis of primary carbamates from alcohols; in vitro and in silico assessments as an alternative acetylcholinesterase inhibitors

Carbamates are important molecules because they are used in various biochemical processes. In this study, effective alternative method for the synthesis of primary carbamates from alcohols was developed in the presence of chlorosulfonyl isocyanate (CSI) in pyridine at room temperature in mild conditions. The primary carbamates were synthesized excellent yield. This method is easy, practical, and inexpensive without any additive, metal, or catalyst. Alzheimer's disease (AD) is a neurodegenerative disease and has been reported to affect approximately 50 million people worldwide in 2020. Drugs that reversibly inhibit the acetylcholinesterase (AChE) activity are used for the treatment of AD. For this reason, there is a growing interest in developing alternative AChE inhibitors. Concordantly, Anti-anticholinesterase activity of synthesized carbamate derivatives was investigated as an alternative AChE inhibitors. In order to determine the inhibitory effect of these molecules, IC50, and Ki values and inhibition types were determined. According to the Ki results, the most effective inhibitors were 3 b and 3e with the Ki values of 22 and 38 µM, respectively. It was found that all molecules showed competitive inhibition type. For clarify the inhibitors-enzyme interactions, molecular docking studies were performed and possible binding interactions between the synthesized molecules and AChE were determined. Additionally, the pharmacokinetic and properties of the synthesized molecules were evaluated in silico.Communicated by Ramaswamy H. Sarma.

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.

Side effects based network construction and drug repositioning of ropinirole as a potential molecule for Alzheimer's disease: an in-silico, in-vitro, and in-vivo study

Alzheimer's disease (AD) is the leading cause of dementia in older adults. Drug repositioning is a process of finding new therapeutic applications for existing drugs. One of the methods in drug repositioning is to use the side-effect profile of a drug to identify a new therapeutic indication. The drugs with similar side-effects may act on similar biological targets and could affect the same biochemical process. In this study, we explored the Food and Drug Administration-approved drugs using PROMISCUOUS database to find those that have adverse effects profile comparable with the ligands being studied or used to treat AD. Here, we found that the ropinirole, a dopamine receptor agonist, shared a maximum number of side-effects with the drugs proven beneficial for treating AD. Furthermore, molecular modelling demonstrated that ropinirole exhibited strong binding affinity (-9.313 kcal/mol) and best ligand efficiency (0.49) with sigma-1 receptor. Here, we observed that the quaternary amino group of ropinirole is essential for binding with sigma-1 receptor. Molecular dynamic simulation indicated that the movement of the carboxy-terminal helices (α4/α5) could play a major role in the receptor's physiological functions. The neurotoxicity induced by Aβ25-35 in SH-SY5Y cells was reduced by ropinirole at concentrations 10, 30, and 50 µM. The effect on spatial learning and memory was examined in mice with Aβ25-35 induced memory deficit using the radial arm maze. Ropinirole (10 and 20 mg/kg) significantly improved the short and long-term memories in the radial arm maze test. Our results suggest that ropinirole has the potential to be repositioned for AD treatment.Communicated by Ramaswamy H. Sarma.

Anti-AChE and Anti-BuChE Screening of the Fermentation Broth Extracts from Twelve Aspergillus Isolates and GC-MS and Molecular Docking Studies of the Most Active Extracts

Nowadays, the administration of cholinesterase enzyme (acetylcholinesterase: AChE and butyrylcholinesterase: BuChE) inhibitors is very common for the symptomatic treatment of Alzheimer's disease and the other forms of dementia and CNS disorders. In this paper, the anti-AChE and anti-BuChE activities of the fermentation broth ethyl acetate extracts from twelve Aspergillus isolates were evaluated by Ellman method. The results showed that A1 (Aspergillus flavus) and A5 (Aspergillus tubingensis, isolate 1) extracts with IC50 values of 46.77 μg/mL and 75.85 μg/mL possess the greatest ability to inhibit AChE and BuChE, respectively. GC-MS analysis of the extracts (A1 and A5) demonstrated that two alkaloids named 14-methyl-16-azabicyclo[10.3.1]hexadeca-1(15),12(16),13-triene (MAHT) and 6-chloro-2-methyl-7,8,9,10-tetrahydro-phenanthridine (CMTP) account for the highest percentage of A1 (26.95%) and A5 (25.5%) extracts, respectively. A 2-pyrazoline derivative, 5-hydroxy-3-(4-pyridinyl)-5-trifluoromethyl-1-(2,4,6-trimethylphenoxyacetyl)- (PHPTT), also constituted the high percentage (9.54%) of A5 extract. The anticholinesterase and neuroprotective effects of some 2-pyrazoline derivatives have been previously reported. The interaction study of MAHT with human AChE and CMTP and PHPTT with human BuChE using molecular docking indicated that these alkaloids bind to the active site gorge of the enzymes with high affinity. The best docking scores of MAHT, CMTP, and PHPTT were -7.1, -8.2, and -9.7 kcal/mol, respectively.

Design, synthesis, and biological evaluation of thienopyrimidine derivatives as multifunctional agents against Alzheimer's disease

A series of 12 S-substituted tetrahydrobenzothienopyrimidines were designed and synthesized based on the donepezil scaffold. All the newly synthesized compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity and the most active compounds were tested for their butyrylcholinesterase (BuChE) inhibitory activity. Moreover, all the synthesized compounds were evaluated for their inhibitory effects against Aβ aggregation and antioxidant activity using the oxygen radical absorbance capacity method. Compounds 4b, 6b, and 8b displayed the most prominent AChE inhibitory action comparable to donepezil. Compound 6b showed the greatest AChE inhibitory action (IC50  = 0.07 ± 0.003 µM) and the most potent BuChE inhibitory action (IC50  = 0.059 ± 0.004 µM). Furthermore, the three compounds exhibited significant antioxidant activity. Compounds 6b and 8b exerted more inhibitory action on Aβ aggregation than donepezil. The cytotoxic activity of compounds 4b, 6b, and 8b against the WI-38 cell line in comparison with donepezil was examined using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. The results revealed that compounds 6b and 8b were less cytotixic than donepezil, while compound 4b showed nonsignificant cytotoxicity compared to donepezil. For more insights about the binding patterns of the most promising compounds (4b, 6b, and 8b) with the AChE at molecular levels; molecular docking and molecular dynamics simulations were performed. The density functional theory calculations and absorption, distribution, metabolism, excretion and toxicity properties were described as well. The results highlighted compound 6b, which incorporates a phenylpiperazine moiety coupled to a thienopyrimidone scaffold via two-atom spacer, to be a promising multifunctional therapeutic agent for the treatment of Alzheimer's disease. It is a potent dual AChE and BuChE inhibitor. Furthermore, it had stronger Aβ aggregation inhibitory action than donepezil. Additionally, compound 6b exerted significant antioxidant activity.

Putting the Puzzle Together To Get the Whole Picture: Molecular Basis of the Affinity of Two Steroid Derivatives to Acetylcholinesterase

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has no cure because its etiology is still unknown, and its main treatment is the administration of acetylcholinesterase (AChE) inhibitors. The study of the mechanism of action of this family of compounds is critical for the design of new more potent and specific inhibitors. In this work, we study the molecular basis of an uncompetitive inhibitor (compound 1, 2β, 3α-dihydroxy-5α-cholestan-6-one disulfate), which we have proved to be a peripheral anionic site (PAS)-binding AChE inhibitor. The pipeline designed in this work is key to the development of other PAS inhibitors that not only inhibit the esterase action of the enzyme but could also modulate the non-cholinergic functions of AChE linked to the process of amylogenesis. Our studies showed that 1 inhibits the enzyme not simply by blocking the main gate but by an allosteric mechanism. A detailed and careful analysis of the ligand binding position and the protein dynamics, particularly regarding their secondary gates and active site, was necessary to conclude this. The same analysis was executed with an inactive analogue (compound 2, 2β, 3α-dihydroxy-5α-cholestan-6-one). Our first computational results showed no differences in affinity to AChE between both steroids, making further analysis necessary. This work highlights the variables to be considered and develops a refined methodology, for the successful design of new potent dual-action drugs for AD, particularly PAS inhibitors, an attractive strategy to combat AD.

Correlation between total phenolic and flavonoid contents and biological activities of 12 ethanolic extracts of Iranian propolis

Propolis is a resinous substance produced by honey bees that is very popular as a natural remedy in traditional medicine. The current research is the first study on the biological properties of ethanolic extracts of propolis (EEP) from several different regions (12) of Iran. Total phenolic and flavonoid contents (TPC and TFC) of Iranian EEPs were variable between 26.59-221.38 mg GAE/g EEP and 4.8-100.03 mg QE/g EEP. The DPPH scavenging assay showed all the studied EEP samples, except for the sample with the lowest TPC and TFC (P6), have suitable antioxidant activity. All the EEPs inhibited both cholinesterase enzymes (acetylcholinesterase: AChE, butyrylcholinesterase: BuChE) but most of them exhibited a distinct selectivity over BuChE. Evaluation of the antibacterial activity of the EEP samples using four pathogenic bacteria (B. cereus, S. aureus, A. baumannii, and P. aeruginosa) demonstrated that the antibacterial properties of propolis are more effective on the gram-positive bacterium. Spearman correlation analysis showed a strong positive correlation between TPC and TFC of the Iranian EEPs and their antioxidant, anticholinesterase, and antibacterial activities. Considering that there is ample evidence of anticholinesterase activity of flavonoids and a significant correlation between the anticholinesterase activity of the studied Iranian EEPs and their total flavonoid content was observed, the interaction of 17 well-known propolis flavonoids with AChE and BuChE was explored using molecular docking. The results indicated that all the flavonoids interact with the active site gorge of both enzymes with high affinity. Summing up, the obtained results suggest that Iranian propolis possesses great potential for further studies.

Molecular Multi-Target Approach for Human Acetylcholinesterase, Butyrylcholinesterase and β-Secretase 1: Next Generation for Alzheimer's Disease Treatment

Alzheimer's Disease (AD) is a neurodegenerative condition characterized by progressive memory loss and other affected cognitive functions. Pharmacological therapy of AD relies on inhibitors of the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), offering only a palliative effect and being incapable of stopping or reversing the neurodegenerative process. However, recent studies have shown that inhibiting the enzyme β-secretase 1 (BACE-1) may be able to stop neurodegeneration, making it a promising target. Considering these three enzymatic targets, it becomes feasible to apply computational techniques to guide the identification and planning of molecules capable of binding to all of them. After virtually screening 2119 molecules from a library, 13 hybrids were built and further screened by triple pharmacophoric model, molecular docking, and molecular dynamics (t = 200 ns). The selected hybrid G meets all stereo-electronic requirements to bind to AChE, BChE, and BACE-1 and offers a promising structure for future synthesis, enzymatic testing, and validation.

Discovery of quinazolin-4(3H)-one derivatives as novel AChE inhibitors with anti-inflammatory activities

A series of quinazolin-4(3H)-one derivatives was designed through scaffold-hopping strategy and synthesized as novel multifunctional anti-AD agents demonstrating both cholinesterase inhibition and anti-inflammatory activities. Their inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were evaluated, and the enzyme kinetics study as well as detailed binding mode via molecular docking were performed for selected compounds. MR2938 (B12) displayed promising AChE inhibitory activity with an IC₅₀ value of 5.04 μM and suppressed NO production obviously (IC₅₀ = 3.29 μM). Besides, it was able to decrease the mRNA levels of pro-inflammatory cytokines IL-1β, TNF-α, IL-6 and CCL2 at 1.25 μM. Further mechanism study suggested that MR2938 suppressed the neuroinflammation through blocking MAPK/JNK and NF-κB signaling pathways. All these results indicate that MR2938 is a good starting point to develop multifunctional anti-AD lead compounds.

Molecular docking studies, anti-Alzheimer's disease, antidiabetic, and anti-acute myeloid leukemia potentials of narcissoside

In this research, we explored their capacity for Narcissoside antioxidant and anticholinergic, antidiabetic, and anti-acute myeloid leukaemia. Narcissoside's antioxidant activities were elucidated by the use of various bioanalytical assays. Narcissoside's radical scavenging activities were evaluated by DPPH^• and ABTS^•+ scavenging activities. On the other hand, IC₅₀ values were calculated for DPPH^•, and ABTS^•+ scavenging, acetylcholinesterase, and α-glucosidase inhibition effects of narcissoside. IC₅₀ values narcissoside, as 11.54 nM for AChE and 65.58 nM for α-glucosidase were calculated with % Activity-[Inhibitory] graphs. Then, ADME/T analysis of narcissoside molecule was performed to calculate the drug becoming parameters.

Absolute configuration of spiro-flavostilbenoids from Yucca schidigera Roezl ex Ortgies: First indication of (2R)-naringenin as the key building block

The absolute configurations of the known but unusual spiro-flavostilbenoids found in the bark of Yucca schidigera Roezl ex Ortgies, were determined by applying time-dependent density functional theory simulation of electronic circular dichroism spectra. The absolute configurations obtained were as follows: (2S,3R) for yuccaol A, yuccaol D and yuccalide A; (2S,3S) for yuccaol B, yuccaol C and yuccaol E; (2S,3S,2'S,3'S) for gloriosaol A; (2S,3R,2'S,3'R) for gloriosaol C; (2S,3S,2'S,3'R) for gloriosaol D; (2S,3R,2'S,3'S) for gloriosaol E. These findings indicate that the compounds are all biosynthetic derivatives either of (2R)-naringenin and trans-resveratrol or of trans-3,3',5,5'-tetrahydroxy-4'-methoxystilbene. In contrast, gloriosaols are direct derivatives of yuccaols (note that substituting by stilbenoid changes the absolute configuration of C-2 naringenin carbon to 2S). A putative mechanism for their biosynthesis is proposed taking into account key aspects of regio- and stereoselectivity. Yuccaol B and gloriosaol A showed in vitro moderate inhibitory effects against acetyl-/butyrylcholinesterases (AChE/BChE) with IC₅₀ values of 43/81 and 45/65 μM respectively. The selectivity index values calculated from the IC₅₀ values of BChE and AChE were 1.9 and 1.4. Molecular docking simulations showed their interaction with the peripheral anionic site of human AChE and the catalytic site of the human BChE.

Structurally diverse alkaloids with nine frameworks from Zephyranthes candida and their acetylcholinesterase inhibitory and anti-inflammatory activities

Twenty-six structurally diverse Amaryllidaceae alkaloids, including ten undescribed compounds named zephyranines A-I and 6-O-ethylnerinine, two undescribed natural products zephyranthine-6-one and 3-O-deacetyl-sternbergine, were isolated from whole plants of Zephyranthes candida. Their structures were determined by HRESIMS, 1D and 2D NMR, CD data analysis, NMR and ECD calculations, and single-crystal X-ray diffraction analysis. All structures were classified into nine framework types: 10b,11-seco-crinine, graciline, crinine, homolycorine, trisphaeridine, lycorine, galasine, tazettine, and belladine. Zephyranine A represents the first naturally occurring 10b,11-seco-crinine type alkaloid, and zephyranine B is the sixth graciline type alkaloid. 6-O-ethylnerinine is an artifact from the extraction and isolation. All isolates were evaluated for their acetylcholinesterase (AChE) inhibitory and anti-inflammatory activities. Zephyranines A, G, and H exhibited moderate AChE inhibitory activities, with IC₅₀ values of 8.2, 39.0, and 10.8 μM, respectively. Zephyranine B, haemanthamine, haemanthidine, 11-hydroxyvittatine, and 8-demethoxy-10-O-methylhostasine exhibited potent anti-inflammatory activity on the LPS-induced NO production in RAW264.7 mouse macrophages with IC₅₀ values of 21.3, 4.6, 12.2, 5.6, and 17.4 μM, respectively. Structure-activity-relationship analysis and docking studies indicated that interactions with the key Trp286 and Tyr337 residues are required for potent AChE inhibitors.

Phenolic Profile and Cholinesterase Inhibitory Properties of Three Chilean Altiplano Plants: Clinopodium gilliesii (Benth.) Kuntze [Lamiaceae], Mutisia acuminata Ruiz & Pav. var. hirsuta (Meyen) Cabrera, and Tagetes multiflora (Kunth) [Asteraceae]

This research aimed to identify the phenolic profile and composition of the aerial parts of three native species used in traditional medicine in the Andean Altiplano of northern Chile: Clinopodium gilliesii (Benth.) Kuntze [Lamiaceae] (commonly known as Muña-Muña), Mutisia acuminata Ruiz & Pav. var. hirsuta (Meyen) Cabrera [Asteraceae] (commonly known as Chinchircoma), and Tagetes multiflora (Kunth), [Asteraceae] (commonly known as Gracilis), as well as to evaluate their potential inhibitory effects against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Polyphenolic enriched-extracts (PEEs) of the species were prepared and analyzed and the main components were quantified using HPLC-DAD. In total, 30 phenolic compounds were identified and quantified in all species, including simple phenolics, hydroxycinnamic acids, flavan-3-ols (monomers and polymers), flavanones, and flavonols. In addition, other main phenolics from the extracts were tentatively identified by ESI-MS-MS high-resolution analysis. T. multiflora extract showed the greatest anti-AChE and BChE activity in comparison with C. gilliesii and M. acuminata extracts, being the anti-AChE and BChE activity weak in all extracts in comparison to galantamine control. To comprise to better understand the interactions between cholinesterase enzymes and the main phenolics identified in T. multiflora, molecular docking analysis was conducted.

Galantamine Based Novel Acetylcholinesterase Enzyme Inhibitors: A Molecular Modeling Design Approach

Acetylcholinesterase (AChE) enzymes play an essential role in the development of Alzheimer's disease (AD). Its excessive activity causes several neuronal problems, particularly psychopathies and neuronal cell death. A bioactive pose on the hAChE B site of the human acetylcholinesterase (hAChE) enzyme employed in this investigation, which was obtained from the Protein Data Bank (PDB ID 4EY6), allowed for the prediction of the binding affinity and free binding energy between the protein and the ligand. Virtual screening was performed to obtain structures similar to Galantamine (GNT) with potential hAChE activity. The top 200 hit compounds were prioritized through the use of filters in ZincPharmer, with special features related to the pharmacophore. Critical analyses were carried out, such as hierarchical clustering analysis (HCA), ADME/Tox predictions, molecular docking, molecular simulation studies, synthetic accessibility (SA), lipophilicity, water solubility, and hot spots to confirm the stable binding of the two promising molecules (ZINC16951574-LMQC2, and ZINC08342556-LMQC5). The metabolism prediction, with metabolites M3-2, which is formed by Glutathionation reaction (Phase II), M1-2, and M2-2 formed from the reaction of S-oxidation and Aliphatic hydroxylation (Phase I), were both reactive but with no side effects. Theoretical synthetic routes and prediction of synthetic accessibility for the most promising compounds are also proposed. In conclusion, this study shows that in silico modeling can be used to create new drug candidate inhibitors for hAChE. The compounds ZINC16951574-LMQC2, and ZINC08342556-LMQC5 are particularly promising for oral administration because they have a favorable drug-likeness profile, excellent lipid solubility, high bioavailability, and adequate pharmacokinetics.

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.