Heterocyclic inhibitors of AChE acylation and peripheral sites

An in vitro study on the interaction of the anti-Alzheimer drug rivastigmine with human erythrocytes

The inhibition of the enzyme acetylcholinesterase (AChE) is a frequently used therapeutic option to treat Alzheimer's disease (AD). By decreasing the levels of acetylcholine degradation in the synaptic space, some cognitive functions of patients suffering from this disease are significantly improved. Rivastigmine is one of the most widely used AChE inhibitors. The objective of this work was to determine the effects of this drug on human erythrocytes, which have a type of AChE in the cell membrane. To that end, human erythrocytes and molecular models of its membrane constituted by dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. They correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. The experimental results obtained by X-ray diffraction and differential scanning calorimetry (DSC) indicated that rivastigmine molecules were able to interact with both phospholipids. Fluorescence spectroscopy results showed that rivastigmine produce a slight change in the acyl chain packing order and a weak displacement of the water molecules of the hydrophobic-hydrophilic membrane interface. On the other hand, observations by scanning electron microscopy (SEM) showed that the drug changed the normal biconcave shape of erythrocytes in stomatocytes (cup-shaped cells) and echinocytes (speculated shaped).

Synthesis and molecular docking studies of some 4-phthalimidobenzenesulfonamide derivatives as acetylcholinesterase and butyrylcholinesterase inhibitors

A series of 4-phthalimidobenzenesulfonamide derivatives were designed, synthesized and evaluated for the inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Structures of the title compounds were confirmed by spectral and elemental analyses. The cholinesterase (ChE) inhibitory activity studies were carried out using Ellman's colorimetric method. The biological activity results revealed that all of the title compounds (except for compound 8) displayed high selectivity against AChE. Among the tested compounds, compound 7 was found to be the most potent against AChE (IC50= 1.35 ± 0.08 μM), while compound 3 exhibited the highest inhibition against BuChE (IC50= 13.41 ± 0.62 μM). Molecular docking studies of the most active compound 7 in AChE showed that this compound can interact with both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE.

Pharmacophore-based design and discovery of (-)-meptazinol carbamates as dual modulators of cholinesterase and amyloidogenesis

Multifunctional carbamate-type acetylcholinesterase (AChE) inhibitors with anti-amyloidogenic properties like phenserine are potential therapeutic agents for Alzheimer's disease (AD). We reported here the design of new carbamates using pharmacophore model strategy to modulate both cholinesterase and amyloidogenesis. A five-feature pharmacophore model was generated based on 25 carbamate-type training set compounds. (-)-Meptazinol carbamates that superimposed well upon the model were designed and synthesized, which exhibited nanomolar AChE inhibitory potency and good anti-amyloidogenic properties in in vitro test. The phenylcarbamate 43 was highly potent (IC₅₀ 31.6 nM) and slightly selective for AChE, and showed low acute toxicity. In enzyme kinetics assay, 43 exhibited uncompetitive inhibition and reacted by pseudo-irreversible mechanism. 43 also showed amyloid-β (Aβ) lowering effects (51.9% decrease of Aβ₄₂) superior to phenserine (31% decrease of total Aβ) in SH-SY5Y-APP₆₉₅ cells at 50 µM. The dual actions of 43 on cholinergic and amyloidogenic pathways indicated potential uses as symptomatic and disease-modifying agents.

Protective effects of a piperazine derivative [N-{4-[4-(2-methoxy-phenyl)-piperazin-1-yl]-phenyl} carbamic acid ethyl ester] against aluminium-induced neurotoxicity: insights from in silico and in vivo studies

The cholinergic hypothesis associated with Alzheimer's disease has spurred the development of numerous structural classes of compounds with different pharmacological profiles aimed at increasing central cholinergic neurotransmission. In the present study, six synthetic piperazine derivatives D1-D6 were screened for their efficacy as acetylcholinesterase inhibitors (AChEIs) through in silico and in vitro studies. Compound D2 was found to be a potential AChEI with adequate pharmacokinetic properties, as supported by in silico study. Further, in vivo studies were designed to examine the protective effect of piperazine derivative D2 (3 and 5 mg/kg for 6 weeks) in ameliorating the alterations induced by aluminium chloride (AlCl(3)) on behavioural and neurochemical indices. Behavioural tests (Morris water maze and elevated plus maze) revealed significant alterations in the short-term memory and anxiety levels in rats treated with AlCl(3), which was further improved after D2 treatment. Further, D2 treatment attenuated the neurotoxic effects of AlCl(3) as shown by the improvement in rats performance in Water maze test and in lowering AChE activity. Besides preventing lipid peroxidation and protein damage, changes in the levels of endogenous antioxidant enzymes (GST, GPx, GR and GSH) associated with AlCl3 administration were also restored upon treatment with D2. Thus, our results support the neuroprotective potential of compound D2, thus validating its use in alleviating toxic effects of aluminium.

Synthesis, molecular modeling and evaluation of novel N'-2-(4-benzylpiperidin-/piperazin-1-yl)acylhydrazone derivatives as dual inhibitors for cholinesterases and Aβ aggregation

To develop new drugs for treatment of Alzheimer's disease, a group of N'-2-(4-Benzylpiperidin-/piperazin-1-yl)acylhydrazones was designed, synthesized and tested for their ability to inhibit acetylcholinesterase, butyrylcholinesterase and aggregation of amyloid beta peptides (1-40, 1-42 and 1-40_1-42). The enzyme inhibition assay results indicated that compounds moderately inhibit both acetylcholinesterase and butyrylcholinesterase. β-Amyloid aggregation results showed that all compounds exhibited remarkable Aβ fibril aggregation inhibition activity with a nearly similar potential as the reference compound rifampicin, which makes them promising anti-Alzheimer drug candidates. Docking experiments were carried out with the aim to understand the interactions of the most active compounds with the active site of the cholinesterase enzymes.

Thione-thiol rearrangement: miyazaki-newman-kwart rearrangement and others

Thione-to-thiol rearrangements represent a general route for the synthesis of sulfur compoundsfrom hydroxyl functionalities. In particular, the Miyazaki-Newman-Kwart rearrangementhas been widely used for the synthesis of aromatic thiols from the corresponding phenols.