Anticholinesterase activity screening of some novel dithiocarbamate derivatives including piperidine and piperazine moieties

Design, synthesis and molecular docking and ADME studies of novel hydrazone derivatives for AChE inhibitory, BBB permeability and antioxidant effects

Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disease that is characterized by memory and cognitive impairments that predominantly affects the elderly and is the most common cause of dementia. As is known, the AChE enzyme consists of two parts. In this work, 10 new hydrazones (3a-3j) were designed and synthesized. Naphthalene, indole, benzofuran and benzothiophene rings were used to interact with the PAS region. 4-fluorophenyl and 4-fluorobenzyl structures were preferred for interaction with the CAS region. In biological activity studies, the AChE and BChE inhibitory potentials of all compounds were evaluated using the in vitro Ellman method. The biological evaluation showed that compounds 3i and 3j displayed significant activity against AChE. The compounds 3i and 3j displayed IC50 values of 0.034 and 0.027 µM against AChE, respectively. The reference drug donepezil (IC50 = 0.021 µM) also displayed a significant inhibition against AChE. In addition, the antioxidant activities of the compounds were also evaluated. Derivatives 3i and 3j, which emerged active from both in vitro activity studies, were subjected to in vitro PAMPA tests to determine BBB permeability. Further docking simulation also revealed that these compounds (3i, 3j and donepezil) interacted with the enzyme active site in a similar manner to donepezil. A few parameters derived from MD simulation trajectories were computed and validated for the protein-ligand complex's stability under the dynamic conditions.Communicated by Ramaswamy H. Sarma.

Synthesis of novel thiosemicarbazone derivatives and investigation of their dual AChE and MAO-B inhibitor effects

In this study, 15 thiosemicarbazone derivatives were synthesized. Analysis of the obtained compounds was performed by means of ¹ H-NMR, ¹³ C-NMR and high resolution mass spectroscopy (HRMS) spectroscopic methods. The inhibition effect of the obtained compounds on cholinesterase and monoaminoxidase (MAO) enzymes were investigated with in vitro methods. None of the compounds showed significant activity on the butyrylcholinesterase enzyme. On the other hand, compounds 3b, 3c, 3e, 3k, 3l, 3m, 3n and 3o displayed significant activity on acetylcholinesterase (AChE) while compounds 3f, 3i, 3k, 3l, 3m, 3n, 3o also showed remarkable effects on monoamine oxidase-B (MAO-B) enzymes. For the selected compounds, docking studies were performed and the enzyme active site and binding modes were determined. It was revealed that the strongest interaction with AChE and MAO-B enzyme active sites was observed with the compound 3k. Another important factor in the treatment of diseases affecting the central nervous system such as Alzheimer's is the ability of the compounds to cross the blood-brain barrier (BBB). Additionally, the agents planned for the treatment of these diseases must also pass the blood-brain barrier. Therefore, in silico BBB penetration properties of active compounds were investigated.

Synthesis of novel benzothiazole derivatives and investigation of their enzyme inhibitory effects against Alzheimer's disease

The use of dual acetylcholinesterase (AChE)-monoamine oxidase B (MAO-B) inhibitors is a new approach in the treatment of Alzheimer disease (AD). In this work, 14 new benzothiazoles (4a-4n) were designed and synthesized. In biological activity studies, the AChE, butyrylcholinesterase (BChE), MAO-A and MAO-B inhibitory potentials of all compounds were evaluated using the in vitro fluorometric method. Additionally, amyloid beta (Aβ)-aggregation inhibitory effects of active compounds were evaluated by means of an in vitro kit-based method. The biological evaluation showed that compounds 4a, 4d, 4f, 4h, 4k and 4m displayed significant activity against AChE and MAO-B enzymes. Compound 4f displayed inhibitory activity against AChE and MAO-B enzyme with IC50 values of 23.4 ± 1.1 nM and 40.3 ± 1.7 nM, respectively. It has been revealed that compound 4f may have the potential to inhibit AChE and MAO-B enzymes, as well as the ability to prevent the formation of beta amyloid plaques accumulated in the brains of patients suffering from AD. In silico studies also support the obtained biological activity findings. Compound 4f provided strong interactions with the active site of both enzymes. In particular, the interaction of compound 4f with flavin adenine dinucleotide (FAD) in the MAO-B enzyme active site is a promising and exciting finding.

Synthesis of new derivatives containing pyridine, investigation of MAO inhibitory activities and molecular docking studies

In this study, novel pyridine-containing thiazolyl hydrazone derivatives were synthesized. Structure determinations of the compounds were performed using ¹H NMR, ¹³C NMR and HRMS techniques. The biological activities of the compounds were evaluated against MAO enzymes by in vitro fluorometric method. As a result of activity studies, compound 3a showed selective inhibitory activity against MAO-B enzyme with IC₅₀ = 0.088 + 0.003 µM. The selectivity index of this compound is greater than 1136. Molecular docking studies were carried out using 2V5Z crystal. It has been observed that docking studies and activity studies are in harmony.

Design, Synthesis, and Evaluation of Novel 2H-Benzo[b][1,4]thiazin-3(4H)-one Derivatives as New Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disease that causes dementia in people aged 65 and over. In the present study, a series of thiadiazole hybrid compounds with benzothiazine derivatives as acetylcholinesterase inhibitors were developed and evaluated for their biological activity. The AChE and BChE inhibition potentials of all compounds were evaluated by using the in vitro Ellman method. The biological evaluation showed that compounds 3i and 3j displayed significant inhibitory activity against AChE. Compounds 3i and 3j showed IC₅₀ values of 0.027 µM and 0.025 µM against AChE, respectively. The reference drug donepezil (IC₅₀ = 0.021 µM) also showed significant inhibition against AChE. Further docking simulation also revealed that these compounds (3i and 3j) interacted with the active site of the enzyme similarly to donepezil. The antioxidant study revealed that compounds 3i and 3j exhibited greater antioxidant effects. An in vitro blood–brain barrier permeability study showed that compounds 3i and 3j are promising compounds against AD. The cytotoxicity study of compounds 3i and 3j showed non-cytotoxic with an IC₅₀ value of 98.29 ± 3.98 µM and 159.68 ± 5.53 µM against NIH/3T3 cells, respectively.

Design, synthesis, biological activity, molecular docking, and molecular dynamics of novel benzimidazole derivatives as potential AChE/MAO-B dual inhibitors

To develop new acetylcholinesterase (AChE)-monoamine oxidase-B (MAO-B) dual inhibitors against Alzheimer's disease, the benzimidazole ring, which has a propargyl side chain with previously proven selective MAO-B inhibitory activity, was used as the main structure. Moreover, like donepezil, it was thought that the enzyme AChE would provide π-π interactions with the peripheral anionic side in this structure. Piperazine derivatives were chosen for the cationic active site. The synthesis of the compounds was carried out in five steps. The structures of the compounds were determined using ¹ H-NMR (nuclear magnetic resonance), ¹³ C-NMR, and high-resolution mass spectrometry spectroscopic methods. First, the in vitro AChE, butyrylcholinesterase (BChE), MAO-A, and MAO-B inhibitory potentials of the obtained compounds were investigated. As a result of activity tests, compounds 5b, 5e, 5g, and 5h showed inhibitory activity against AChE; compounds 5e and 5g showed inhibitory activity against MAO-B. None of the compounds showed inhibitory activity against BChE or MAO-A. Compounds 5e and 5g showed dual inhibition. Among these compounds, compound 5g had inhibition potential similar to that of donepezil and selegiline. For compound 5g, further kinetic studies and Aβ-plaque inhibitory potentials were investigated using in vitro methods. Molecular docking studies were performed using both AChE and hMAO-B crystals to elucidate the compound's interactions with the enzyme active site. The binding modes of the compound on AChE were fully elucidated by molecular dynamics studies.

Design and synthesis of novel chalcone derivatives and evaluation of their inhibitory activities against acetylcholinesterase

According to the cholinergic hypothesis, an increase in the acetylcholine level in Alzheimer's disease patients relatively slows down the symptoms of the disease. The most commonly used drug, donepezil, is a cholinesterase inhibitor. In this study, 12 new chalcones (2a-l) were designed and synthesized. In biological activity studies, the acetylcholinesterase (AChE) and butyrylcholinesterase inhibitory potentials of all compounds were evaluated using the in vitro Ellman method. The biological evaluation showed that compounds 2d, 2f, 2j, and 2l displayed significant activity against AChE. The compounds 2d, 2f, 2j, and 2l displayed IC₅₀ values of 0.042, 0.024, 0.053, and 0.033 µM against AChE, respectively. The reference drug donepezil (IC₅₀  = 0.021 µM) also displayed significant inhibition of AChE. The inhibitory activities of these compounds for β-amyloid plaque aggregation were investigated. The enzyme kinetic study was performed to observe the effect of the most active compound 2f on the substrate-enzyme relationship, and a mixed-type inhibition of AchE was determined. Further, docking simulation also revealed that these compounds (2d, 2f, 2j, and 2l) interacted with the enzyme active site in a similar manner to donepezil. The most active derivative, compound 2f, interacted with the amino acids Trp286, Phe295, Tyr341, Trp86, and Glu202.

Dithiocarbamate derivatives inhibit α-glucosidase through an apparent allosteric site on the enzyme

Dithiocarbamate derivatives possess diverse biological activities. This work further expands their activity profile by identifying seven benzylamine-containing dithiocarbamate derivatives with piperazine and piperidine substitutions at the main moiety, and five piperazine-containing dithiocarbamates with various substitutions at the piperazine moiety as new inhibitors of α-glucosidase. Compounds bearing the benzylamine moiety exhibited more potent inhibition of the enzyme than the piperazine derivatives. Majority of the compounds non-competitively inhibited α-glucosidase that led to the identification of a new allosteric site on the enzyme with the help of molecular dynamics and docking studies. These studies suggest that the compounds regulate inhibition of the enzyme by binding to an allosteric site that is located in the vicinity of the active site. This is the first report on the allosteric inhibition of α-glucosidase by dithiocarbamate derivatives that provides insights into the mechanism of inhibition of the enzyme at molecular level. Moreover, it also explores new avenues for drug development of α-glucosidase inhibitors as antidiabetic drugs.

Design, Synthesis, and Structure-Activity Relationships of Thiazole Analogs as Anticholinesterase Agents for Alzheimer's Disease

Dementia is a neurological condition commonly correlated with Alzheimer's disease (AD), and it is seen with many other central nervous system (CNS) disorders. The restricted number of medications is not appropriate to offer enough relief to enhance the quality of life of patients suffering from this symptom; thus, all therapeutic choices should be carefully assessed. In this study, new thiazolylhydrazone derivatives (2a-2l) were designed and synthesized based on the cholinergic hypothesis. Their chemical structures were confirmed by 1H NMR, 13C NMR, and HRMS spectrometric techniques. The ADME (absorption, distribution, metabolism, elimination) parameters of the synthesized compounds were predicted by using QikProp 4.8 software. It was concluded that all compounds presented satisfactory drug-like characteristics. Furthermore, their inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro were also tested by modified the Ellman spectrophotometric method. According to the results, all compounds showed a weak inhibitory effect on BChE. On the other hand, most of the compounds (2a, 2b, 2d, 2e, 2g, 2i, and 2j) had a certain AChE inhibitory activity, and the IC50 values of them were calculated as 0.063 ± 0.003, 0.056 ± 0.002, 0.147 ± 0.006, 0.040 ± 0.001, 0.031 ± 0.001, 0.028 ± 0.001, and 0.138 ± 0.005 µM, respectively. Among these derivatives, compound 2i was found to be the most active agent in the series with an IC50 value of 0.028 ± 0.001 µM, which indicated an inhibition profile at a similar rate as the reference drug, donepezil. The potential binding modes of compounds 2a, 2b, 2e, 2g, and 2i with AChE were investigated and compared with each other by the molecular docking studies. The results showed that these compounds were strongly bound up with the AChE enzyme active site with the optimal conformations.

Design, Synthesis, and Biological Activity Evaluation of New Donepezil-Like Compounds Bearing Thiazole Ring for the Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is a progressive and neurodegenerative disease that is primarily seen in the elderly population and is clinically characterized by memory and cognitive impairment. The importance of the disease has increased as a result of etiology of the disease having not yet been determined, an increase in patient population over the years, absence of radical treatment, high cost of treatment and care, and significant reduction in the quality of life of the patients, which have led researchers to direct more attention to this field. In a recent study, new indan-thiazolylhydrazone derivatives were designed and synthesized based on the chemical structure of the donepezil molecule, which is the most preferred and has the most appropriate response in the treatment of AD. The structures of the compounds were determined by 1H-NMR and 13C-NMR, and mass spectroscopic methods. Inhibition studies on the cholinesterase (ChE) enzymes and beta amyloid plaque inhibition test of the compounds were performed. Among the synthesized derivatives, compounds 2a, 2e, 2i, and 2l showed potent inhibitory activity on the AChE enzyme. Compound 2e was found to be the most active agent, with an IC50 value of 0.026 µM. The mechanism of AChE inhibition by compound 2e was studied using the Lineweaver-Burk plot, and the nature of inhibition was also determined to be mix-typed. Molecular docking studies were also carried out for compound 2e, which was found as the most potent agent within the AChE enzyme active site. Moreover, compounds 2a, 2e, 2i, and 2l displayed the ability to prevent beta amyloid plaque aggregation at varying rates. In addition, ADME (Absorption, Distribution, Metabolism, Elimination) parameters were evaluated for all synthesized compounds using the QikProp 4.8 software (Schrödinger Inc., NY, USA).

Synthesis and Biological Evaluation of New Cholinesterase Inhibitors for Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder mostly influencing the elderly, and causes death due to dementia. The main pathogenic feature connected with the progression of this multifactorial disease is the weakening of the cholinergic system in the brain. Cholinesterase (ChE) inhibitors are recognized as one of the choices in the treatment of AD. The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were approved as a therapeutic strategy to reduce the symptoms of AD and prevent its progression. The capacity of BChE is not completely known yet; rather, it is accepted to assume a part in a few disorders such as AD. Thus, BChE inhibitors may have a greater role for the treatment of AD in the future. In the present study, 2-(9-acridinylamino)-2-oxoethyl piperazine/piperidine/morpholinecarbodithioate derivatives were synthesized in order to investigate anticholinesterase activity. Eight derivatives demonstrated a specific and promising action against BChE. Furthermore, compound 4n showed inhibitory activity against both enzymes. It was found that the active compounds were well tolerated in the cytotoxicity test. Possible interactions between the lead compound, 4n, and the BChE enzyme were determined through a docking study. The findings obtained within this paper will contribute to the development of new and effective synthetic anti-Alzheimer compounds, and will ideally encourage future screening against AD.