Design and synthesis of N-benzylpiperidine–purine derivatives as new dual inhibitors of acetyl- and butyrylcholinesterase

Hydrosilylation of nitriles and tertiary amides using a zinc precursor

We report a competent and selective hydrosilylation of nitriles and tertiary amides catalyzed by the readily available zinc bis(hexamethyldisilazide) under solvent-free and mild conditions, making it a sustainable and desirable alternative to existing methods. Both protocols afforded high conversion, superior selectivity, and a broad substrate scope, from electron-withdrawing to electron-donating and heterocyclic substitutions.

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.

Design, synthesis, anticancer and in silico assessment of 8-caffeinyl-triazolylmethoxy hybrid conjugates

In this research the synthesis, characterization, anticancer and the cytotoxicity assessments of novel 8-caffeinyl-triazolylmethoxy hybrid conjugates have been described. These compounds are the first caffeine-1,2,3-triazolyl hybrid molecules that structurally are composed of three compartments comprising caffeinyl, 1,2,3-triazolyl and N-alkyl/aryl residues. The in vitro evaluations of synthesized compounds on cancer cell lines, including two breast cancer cell lines MDA-MB-468 (ATCC HTB-22), MCF-7 (ATCC HTB-22), melanoma cell line A-375 (ATCC CRL-1619) and normal cell line HEK-293 (ATCC CRL-11268) have determined that 22c (IC₅₀ < 12.5 μM) demonstrated potent activity against A375 and its toxicity is even stronger than methotrexate (MTX) as a standard drug. Additionally, 22c involves more selectivity than MTX regarding its non-toxicity for the HEK-293 cell line. Among the tested compounds against two breast cancer cell lines, 22f (IC₅₀ = 136 ± 0.2 and 126 ± 0.6 μM for MCF-7 and MDA-MB-468, respectively) and 22i (IC₅₀ = 165 ± 1.8 and 175 ± 1.4 μM for MCF-7 and MDA-MB-468, respectively) were the most potent compounds but their activities were less than MTX, moreover 22f showed more selectivity regarding its lower toxicity against HEK-293. Overall, 22f displayed general toxicity and selectivity on all tested cancer cell lines. The in silico physicochemical properties, pharmacokinetic profile, and drug likeness predictions were also carried out for all the studied compounds. Most new compounds exhibited zero violation of Lipinski's rule (RO5). A molecular docking study was also conducted to predict the binding mode and the interaction of 22c as the most active anti-melanoma entry with B-RAF V600E kinase enzyme. The docking results determined that 22c exhibited a strong binding affinity to the active site of the enzyme. These findings demonstrated 22c and 22f as potential future anticancer drug candidates.

A Novel Donepezil–Caffeic Acid Hybrid: Synthesis, Biological Evaluation, and Molecular Docking Studies

A novel donepezil-caffeic acid (DP-CA) hybrid molecule was designed, synthesis, and investigated by molecular modeling. Its biological activity and protective effect were investigated by the IR spectroscopy, ¹H and ¹³C NMR spectroscopy, and mass spectrometry. DP-CA was highly active against acetylcholine esterase and inhibited it at the micromolar concentrations. Fluorescence and UV-Vis spectroscopy studies showed strong binding of DP-CA to DNA. Moreover, DP-CA exhibited protective effects against H2O2-induced toxicity in U-118 MG glioblastoma cells. Finally, molecular docking showed a high affinity of DP-CA in all concentrations, and the active 4EY7 site exhibited essential residues with polar and apolar contacts. Taken together, these findings indicate that DP-CA could be a prospective multifunctional agent for the treatment of neurodegenerative diseases.

Design, Synthesis and Assay of Novel Methylxanthine-Alkynylmethylamine Derivatives as Acetylcholinesterase Inhibitors

Xanthine derivatives have been a great area of interest for the development of potent bioactive agents. Thirty-eight methylxanthine derivatives as acetylcholinesterase inhibitors (AChE) were designed and synthesized. Suzuki-Miyaura cross-coupling reactions of 8-chlorocaffeine with aryl(hetaryl)boronic acids, the CuAAC reaction of 8-ethynylcaffeine with several azides, and the copper(I) catalyzed one-pot three-component reaction (A³-coupling) of 8-ethynylcaffeine, 1-(prop-2-ynyl)-, or 7-(prop-2-ynyl)-dimethylxanthines with formaldehyde and secondary amines were the main approaches for the synthesis of substituted methylxanthine derivatives (yield 53-96%). The bioactivity of all new compounds was evaluated by Ellman's method, and the results showed that most of the synthesized compounds displayed good and moderate acetylcholinesterase (AChE) inhibitory activities in vitro. The structure-activity relationships were also discussed. The data revealed that compounds 53, 59, 65, 66, and 69 exhibited the most potent inhibitory activity against AChE with IC₅₀ of 0.25, 0.552, 0.089, 0.746, and 0.121 μM, respectively. The binding conformation and simultaneous interaction modes were further clarified by molecular docking studies.

Synthesis and molecular modelling of thiadizole based hydrazone derivatives as acetylcholinesterase and butyrylcholinesterase inhibitory activities

Some novel substituted thiazolylhydrazine derivatives were designed, synthesized and their inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes and antioxidant activities were investigated. The structures of the synthesized compounds were determined using different spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, and HRMS. According to the enzyme inhibition results, the synthesized compounds showed selectivity against BuChE enzyme inhibition. Compounds 5e, 5g, 5i and 5j displayed significant BuChE inhibition potencies. Among them, compound 5i was found to be the most effective derivative with an IC₅₀ value of 56.01 ± 0.054 µM. In addition, their antioxidant properties were evaluated in vitro through the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. For compounds 5e, 5g, 5i and 5j in silico molecular docking and 100 ns molecular dynamics simulations studies against the BuChE enzyme were performed to determine possible protein-ligand interactions and stability. DFT-D3 study was performed to stabilize of compounds 5e, 5g, 5i and 5j both in gas and solvent medium and investigated their electronic properties. Of all geometries, that of DMSO is the lowest one.

Identification of Compounds for Butyrylcholinesterase Inhibition

Butyrylcholinesterase (BChE) is a nonspecific cholinesterase enzyme that hydrolyzes choline-based esters. BChE plays a critical role in maintaining normal cholinergic function like acetylcholinesterase (AChE) through hydrolyzing acetylcholine (ACh). Selective BChE inhibition has been regarded as a viable therapeutic approach in Alzheimer's disease. As of now, a limited number of selective BChE inhibitors are available. To identify BChE inhibitors rapidly and efficiently, we have screened 8998 compounds from several annotated libraries against an enzyme-based BChE inhibition assay in a quantitative high-throughput screening (qHTS) format. From the primary screening, we identified a group of 125 compounds that were further confirmed to inhibit BChE activity, including previously reported BChE inhibitors (e.g., bambuterol and rivastigmine) and potential novel BChE inhibitors (e.g., pancuronium bromide and NNC 756), representing diverse structural classes. These BChE inhibitors were also tested for their selectivity by comparing their IC50 values in BChE and AChE inhibition assays. The binding modes of these compounds were further studied using molecular docking analyses to identify the differences between the interactions of these BChE inhibitors within the active sites of AChE and BChE. Our qHTS approach allowed us to establish a robust and reliable process to screen large compound collections for potential BChE inhibitors.

Highlights of ASS234: a novel and promising therapeutic agent for Alzheimer's disease therapy

There is no effective treatment to face Alzheimer’s disease complexity. Multitarget molecules are a good approach against the multiple physiopathological events associated with its development and progression. In this context, N-((5-(3-(1-benzylpiperidin-4-yl) propoxy)-1- methyl-1H-indol-2-yl)methyl)-N-methylprop-2-yn-1-amine (ASS234) has been tested achieving promising results. ASS234 has demonstrated to cross the blood-brain barrier in vivo, and a good in silico safety profile being less toxic than donepezil. Besides, ASS234 reversibly inhibits human acetyl- and butyryl-cholinesterase, and irreversibly inhibits human monoamine oxidase A and B. Moreover, this multitarget molecule has antioxidant and neuroprotective properties, and inhibits Αβ_1–42 and Αβ_1–40 self-aggregation. Inquiring about the mechanism of action, several signaling pathways related to Alzheimer’s disease had been explored showing that ASS234 induces the wingless-type MMTV integration site (Wnt) family and several members of the heat shock proteins family and moreover counteracts neuroinflammatory and oxidative stress-related genes promoting the induction of several key antioxidant genes. Finally, in vivo experiments with ASS234 in C57BL/6J mice displayed its ability to reduce amyloid plaque burden and gliosis in the cortex and hippocampus, ameliorating scopolamine-induced learning deficits. Here we gather the information regarding ASS234 evaluated so far, showing its ability to face different targets, necessary to counteract a neurodegenerative disease as complex as the Alzheimer’s disease.

A Systematic Review on Donepezil-based Derivatives as Potential Cholinesterase Inhibitors for Alzheimer’s Disease

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Alzheimer’s Disease (AD) is a multifactorial progressive neurodegenerative disorder characterized by memory loss, disorientation, and gradual deterioration of intellectual capacity. Its etiology has not been elucidated yet. To date, only one therapeutic approach has been approved for the treatment of AD. The pharmacotherapy of AD has relied on noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist - memantine, and acetylcholinesterase (AChE) inhibitors (AChEIs) - tacrine, donepezil, rivastigmine and galantamine. Donepezil was able to ameliorate the symptoms related to AD mainly via AChE, but also through reduction of β-amyloid burden. This review presents the overview of donepezilrelated compounds as potential anti-AD drugs developed on the basis of cholinergic hypothesis to act as solely AChE and butyrylcholinesterase (BChE) inhibitors.

Non-covalent interactions between thio-caffeine derivatives and water-soluble porphyrin in ethanol-water environment

To determine the binding interactions and ability to form the non-covalent systems, the association process between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H₂TTMePP) and a series of five structurally diverse thio-caffeine analogues has been studied in ethanol and ethanol-water solutions, analyzing its absorption and steady-state fluorescence spectra. The porphyrin fluorescence lifetimes in the systems studied were established as well. During the titration with thio-caffeine compounds the slight bathochromic effect and considerable hypochromicity of the porphyrin Soret band maximum can be noted. The fluorescence quenching effect observed for interactions in H₂TTMePP - thio-caffeine derivative systems, as well as the order of binding and fluorescence quenching constants (of 10⁵-10³mol^-1) suggest the existence of the mechanism of static quenching due to the formation of non-covalent and non-fluorescent stacking complexes. In all the systems studied the phenomenon of the fractional accessibility of the fluorophore for the quencher was observed as well. Additionally, the specific binding interactions, due to the changes in reaction environment polarity, can be observed. It was found that thio-caffeine compounds can quench the porphyrin fluorescence according to the structure of thio-substituent in caffeine molecule. The obtained results can be potentially useful from scientific, therapeutic or environmental points of view.

QSAR model for prediction of the therapeutic potency of N-benzylpiperidine derivatives as AChE inhibitors

A new family of AChE inhibitors, N-benzylpiperidines, showed exceptional efficacy in vitro and in vivo, minimal side effects and high selectivity for acetylcholinesterase (AChE). Three regression methods were chosen in this work to develop robust predictive models, namely multiple linear regression (MLR), genetic function approximation (GFA) and multilayer perceptron network (MLP). Ten descriptors were selected for a dataset of 99 molecules, using a genetic algorithm. The best results were obtained for MLP with a 10-6-1 artificial neural network model trained with the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. Statistical prediction for MLR and GFA were r² = 0.882 and r² = 0.875, respectively. Because internal and external validation strategies play an important role, we adopted all available validation strategies to check the robustness of the models. All criteria used to validate these models revealed the superiority of the GFA model. Therefore, the models developed in this study provide an excellent prediction of the inhibitory concentration of a new family of AChE inhibitors.

N-Methyl-β-carbolinium Salts and an N-Methylated 8-Oxoisoguanine as Acetylcholinesterase Inhibitors from a Solitary Ascidian, Cnemidocarpa irene

New brominated β-carbolines irenecarbolines A (1) and B (4) along with known β-carbolines 2 and 3 and a new 8-oxoisoguanine derivative, 5, were isolated from a solitary ascidian, Cnemidocarpa irene. The structures of these compounds were determined on the basis of their spectral data. All, except for 3, inhibited the action of acetylcholinesterase (AchE). The activities of 1 and 5 were comparable to those of galantamine, a clinically used AchE inhibitor. Compounds 1 and 2 were found to be present in high concentrations in blood, and fluorescence was observed in certain types of cells found in the blood of the tunicate.

Recent progress in repositioning Alzheimer's disease drugs based on a multitarget strategy

Alzheimer's disease (AD) is a serious progressive neurological disorder, characterized by impaired cognition and profound irreversible memory loss. The multifactorial nature of AD and the absence of a cure so far have stimulated medicinal chemists worldwide to follow multitarget drug-design strategies based on repositioning approved drugs. This review describes a summary of recently published works focused on tailoring new derivatives of US FDA-approved acetylcholinesterase inhibitors, in addition to huperzine (a drug approved in China), either by hybridization with other pharmacophore elements (to hit more AD targets), or by combination of two FDA-approved drugs. Besides the capacity for improving the cholinergic activity, these polyfunctional derivatives are also able to tackle other important neuroprotective properties, such as anti-β-amyloid aggregation, scavenging of radical oxygen species, modulation of redox-active metals or inhibition of monoamine oxidase, thereby resulting in potentially novel and more effective therapeutics for the treatment of AD.

Donepezil + propargylamine + 8-hydroxyquinoline hybrids as new multifunctional metal-chelators, ChE and MAO inhibitors for the potential treatment of Alzheimer's disease

The synthesis, biochemical evaluation, ADMET, toxicity and molecular modeling of novel multi-target-directed Donepezil + Propargylamine + 8-Hydroxyquinoline (DPH) hybrids 1-7 for the potential prevention and treatment of Alzheimer's disease is described. The most interesting derivative was racemic α-aminotrile4-(1-benzylpiperidin-4-yl)-2-(((8-hydroxyquinolin-5-yl)methyl)(prop-2-yn-1-yl)amino) butanenitrile (DPH6) [MAO A (IC50 = 6.2 ± 0.7 μM; MAO B (IC50 = 10.2 ± 0.9 μM); AChE (IC50 = 1.8 ± 0.1 μM); BuChE (IC50 = 1.6 ± 0.25 μM)], an irreversible MAO A/B inhibitor and mixed-type AChE inhibitor with metal-chelating properties. According to docking studies, both DPH6 enantiomers interact simultaneously with the catalytic and peripheral site of EeAChE through a linker of appropriate length, supporting the observed mixed-type AChE inhibition. Both enantiomers exhibited a relatively similar position of both hydroxyquinoline and benzyl moieties with the rest of the molecule easily accommodated in the relatively large cavity of MAO A. For MAO B, the quinoline system was hosted at the cavity entrance whereas for MAO A this system occupied the substrate cavity. In this disposition the quinoline moiety interacted directly with the FAD aromatic ring. Very similar binding affinity values were also observed for both enantiomers with ChE and MAO enzymes. DPH derivatives exhibited moderate to good ADMET properties and brain penetration capacity for CNS activity. DPH6 was less toxic than donepezil at high concentrations; while at low concentrations both displayed a similar cell viability profile. Finally, in a passive avoidance task, the antiamnesic effect of DPH6 was tested on mice with experimentally induced amnesia. DPH6 was capable to significantly decrease scopolamine-induced learning deficits in healthy adult mice.

Synthesis, evaluation and molecular dynamics study of some new 4-aminopyridine semicarbazones as an antiamnesic and cognition enhancing agents

Some new semicarbazones of 4-aminopyridine were synthesized and evaluated for antiamnesic, cognition enhancing and anticholinesterase activities. The results illustrated a significant cognition enhancing effect on elevated plus maze model with a significant reversal of scopolamine-induced amnesia. A significant inhibition in acetycholinesterase (AChE) activity by all the synthesized compounds in specific brain regions that is, prefrontal cortex, hippocampus and hypothalamus was observed. Compound 4APi exhibited significant antiamnesic and cognition enhancing activity which was comparable with standard drug donepezil. Its enzyme kinetic study revealed a non-competitive inhibition of AChE and a competitive inhibition of butyrylcholinesterase (BChE). Docking studies predicted the binding modes of these compounds in AChE active site, which were further processed for molecular dynamics simulation for calculating binding free energies using Molecular Mechanics-Generalized Born Surface Area (MM/GBSA). All the computational study confirmed their consensual interaction with AChE justifying the experimental outcome.

Synthesis, biological evaluation and molecular modeling of substituted 2-aminobenzimidazoles as novel inhibitors of acetylcholinesterase and butyrylcholinesterase

A series of novel 2-aminobenzimidazole derivatives were synthesized under microwave irradiation. Their biological activities were evaluated on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A number of the 2-aminobenzimidazole derivatives showed good inhibitory activities to AChE and BuChE. Among them, compounds 9, 12 and 13 were found to be >25-fold more selective for BuChE than AChE. No evidence of cytotoxicity was observed by MTT assay in PC12 cells or HepG2 cells exposed to 100μM of the compounds. Molecular modeling studies indicate that the benzimidazole moiety of compounds 9, 12 and 13 forms a face-to-face π-π stacking interaction in a 'sandwich' form with the indole ring of Trp82 (4.09Å) in the active gorge, and compounds 12 and 13 form a hydrogen bond with His438 at the catalytic site of BuChE. In addition, compounds 12 and 13 fit well into the hydrophobic pocket formed by Ala328, Trp430 and Tyr332 of BuChE. Our data suggest the 2-aminobenzimidazole drugs as promising new selective inhibitors for AChE and BuChE, potentially useful to treat neurodegenerative diseases.

Inhibition of acetylcholinesterase by green and white tea and their simulated intestinal metabolites

By 2034 it is forecast that 5% of the global population will be aged 85 years or over--approximately two and half fold increase on present day figures--which will inevitably lead to an increase in age-associated disorders such as Alzheimer's disease. There is mounting evidence that green tea (Camellia sinensis) possesses numerous health-promoting properties, and may potentially be beneficial to those suffering from Alzheimer's and other diseases, including cardiovascular disease and cancer. These beneficial properties are largely attributed to the high polyphenol content, particularly the catechins. In this study, we measured acetylcholinesterase inhibition by white and green teas and their simulated intestinal digests. We found that the potency with which the white and green tea extracts inhibited acetylcholinesterase varied through the simulated digestion procedure. Initially, in the undigested extract form, potency was high with IC₅₀ values of 7.20 μg mL⁻¹ and 8.06 μg mL⁻¹ for green and white tea respectively.However, this decreased significantly after gastric digestion but activity was recovered after pancreatic digestion which could be related to relative increases in the levels of caffeine and specific phenolic components. Of the pure tea compounds tested, EGCG was the most potent with an IC₅₀ of 0.0096 μmol mL⁻¹ but its breakdown product; γ-valerolactone was the least potent analyte. Particularly interesting were the results of caffeine,which exhibited a strong inhibitory activity and pyrogallol, which recorded a much stronger potency than its parent compound gallic acid, suggesting a pro-drug-like relationship. Overall, the results indicate that further research is necessary to determine the full potential of digestion of tea and its metabolites and how inter-individual variation may indicate that some sections of society could potentially benefit more from drinking tea as a strategy to prevent the development of dementia. We have also shown the activities of a number of metabolites,however, further research is required to determine their potential bioavailability.

Synthesis, biological evaluation, and molecular modeling of donepezil and N-[(5-(benzyloxy)-1-methyl-1H-indol-2-yl)methyl]-N-methylprop-2-yn-1-amine hybrids as new multipotent cholinesterase/monoamine oxidase inhibitors for the treatment of Alzheimer's disease

A new family of multitarget molecules able to interact with acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), as well as with monoamino oxidase (MAO) A and B, has been synthesized. Novel compounds (3-9) have been designed using a conjunctive approach that combines the benzylpiperidine moiety of the AChE inhibitor donepezil (1) and the indolyl propargylamino moiety of the MAO inhibitor N-[(5-benzyloxy-1-methyl-1H-indol-2-yl)methyl]-N-methylprop-2-yn-1-amine (2), connected through an oligomethylene linker. The most promising hybrid (5) is a potent inhibitor of both MAO-A (IC50=5.2±1.1 nM) and MAO-B (IC50=43±8.0 nM) and is a moderately potent inhibitor of AChE (IC50=0.35±0.01 μM) and BuChE (IC50=0.46±0.06 μM). Moreover, molecular modeling and kinetic studies support the dual binding site to AChE, which explains the inhibitory effect exerted on Aβ aggregation. Overall, the results suggest that the new compounds are promising multitarget drug candidates with potential impact for Alzheimer's disease therapy.

4-Aryl-4-oxo-N-phenyl-2-aminylbutyramides as acetyl- and butyrylcholinesterase inhibitors. Preparation, anticholinesterase activity, docking study, and 3D structure-activity relationship based on molecular interaction fields

Synthesis and anticholinesterase activity of 4-aryl-4-oxo-N-phenyl-2-aminylbutyramides, novel class of reversible, moderately potent cholinesterase inhibitors, are reported. Simple substituent variation on aroyl moiety changes anti-AChE activity for two orders of magnitude; also substitution and type of hetero(ali)cycle in position 2 of butanoic moiety govern AChE/BChE selectivity. The most potent compounds showed mixed-type inhibition, indicating their binding to free enzyme and enzyme-substrate complex. Alignment-independent 3D QSAR study on reported compounds, and compounds having similar potencies obtained from the literature, confirmed that alkyl substitution on aroyl moiety of molecules is requisite for inhibition activity. The presence of hydrophobic moiety at close distance from hydrogen bond acceptor has favorable influence on inhibition potency. Docking studies show that compounds probably bind in the middle of the AChE active site gorge, but are buried deeper inside BChE active site gorge, as a consequence of larger BChE gorge void.

Novel 16-substituted bifunctional derivatives of huperzine B: multifunctional cholinesterase inhibitors

AIM

To design novel bifunctional derivatives of huperzine B (HupB) based on the concept of dual binding site of acetylcholinesterase (AChE) and evaluate their pharmacological activities for seeking new drug candidates against Alzheimer's disease (AD).

METHODS

Novel 16-substituted bifunctional derivatives of HupB were synthesized through chemical reactions. The inhibitory activities of the derivatives toward AChE and butyrylcholinesterase (BuChE) were determined in vitro by modified Ellman's method. Cell viability was quantified by the reduction of MTT.

RESULTS

A new preparative method was developed for the generation of 16-substituted derivatives of HupB, and pharmacological trials indicated that the derivatives were multifunctional cholinesterase inhibitors targeting both AChE and BuChE. Among the derivatives tested, 9c, 9e, 9f, and 9i were 480 to 1360 times more potent as AChE inhibitors and 370 to 1560 times more potent as BuChE inhibitors than the parent HupB. Further preliminary pharmacological trials of derivatives 9c and 9i were performed, including examining the mechanism of AChE inhibition, the substrate kinetics of the enzyme inhibition, and protection against hydrogen peroxide (H2O2)-induced cytotoxicity in PC12 cells.

CONCLUSION

Preliminary pharmacological evaluation indicated that 16-substituted derivatives of HupB, particularly 9c and 9i, would be potentially valuable new drug candidates for AD therapy, and further exploration is needed to evaluate their pharmacological and clinical efficacies.

Molecular interactions of cholinesterases inhibitors using in silico methods: current status and future prospects

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a low amount of acetylcholine (ACh) in hippocampus and cortex. Acetylcholinesterase (AChE) is one of the most important enzymes in many living organisms including human being and other vertebrates, insects like mosquitoes, among others. Several reports have been published where it has been clearly shown that the genesis of amyloid protein plaques associated with AD is connected to modifications of both AChE and butyrylcholinesterase (BChE), since the plaque is significantly decreased in AD patients using cholinesterase inhibitors (ChEIs). This review gives some examples of these inhibitors discovered during past couple of years that have shown very prominent interactions at the active site triad of the proteins as well as different other parts of the active site like, peripheral anionic site (PAS), oxyanionic hole, anionic subsite or acyl binding pocket (ABP). Most of the inhibition and their interactions have been visualized by X-ray crystallography, but some of the other inhibitors have been studied either by molecular docking or molecular dynamic (MD) simulations or by both the in silico methods. Some of these prominent studies have been crucially observed and reported here.

Design, synthesis and biological evaluation of novel dual inhibitors of acetylcholinesterase and beta-secretase

To explore novel effective drugs for the treatment of Alzheimer's disease (AD), a series of dual inhibitors of acetylcholineterase (AChE) and beta-secretase (BACE-1) were designed based on the multi-target-directed ligands strategy. Among them, inhibitor 28 exhibited good dual potency in enzyme inhibitory potency assay (BACE-1: IC(50)=0.567 microM; AChE: IC(50)=1.83 microM), and also showed excellent inhibitory effects on Abeta production of APP transfected HEK293 cells (IC(50)=98.7 nM) and mild protective effect against hydrogen peroxide (H(2)O(2))-induced PC12 cell injury. Encouragingly, intracerebroventricular injection of 28 into amyloid precursor protein (APP) transgenic mice caused a 29% reduction of Abeta(1-40) production. Therefore, 28 was demonstrated as a good lead compound for the further study and more importantly, the strategy of AChE and BACE-1 dual inhibitors might be a promising direction for developing novel drugs for AD patients.

Novel Tacrine−Melatonin Hybrids as Dual-Acting Drugs for Alzheimer Disease, with Improved Acetylcholinesterase Inhibitory and Antioxidant Properties

Tacrine and melatonin are well-known drugs with activities as an acetylcholinesterase (AChE) inhibitor and free radical scavenger, respectively. In this work, we report new hybrids of both drugs that display higher in vitro properties than the sum of their parts. As selective inhibitors of human AChE, their IC(50) values range from sub-nanomolar to picomolar. They exhibit a higher oxygen radical absorbance capacity than does melatonin and are predicted to be able to cross the blood-brain barrier to reach their targets in the central nervous system.