QuinoxalineTacrine QT78, a Cholinesterase Inhibitor as a Potential Ligand for Alzheimer's Disease Therapy

1,2,3-Triazolo[4,5-b]aminoquinolines: Design, synthesis, structure, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, and molecular docking of novel modified tacrines

An efficient [4 + 2] cyclization protocol to synthesize a series of twelve examples of 1,2,3-triazolo[4,5-b]aminoquinolines (5) as novel structurally modified tacrines was obtained by reacting readily accessible precursors (i.e., 3-alky(aryl)-5-amino-1,2,3-triazole-4-carbonitriles (3)) and selected cycloalkanones (4) of five-, six-, and seven-membered rings. We evaluated the AChE and BChE inhibitory activity of the novel modified tacrines 5, and the compound derivatives from cyclohexanone (4b) showed the best AChE and BChE inhibitory activities. Specifically, 1,2,3-triazolo[4,5-b]aminoquinolines 5bb obtained from 3-methyl-carbonitrile (3b) showed the highest AChE (IC50 = 12.01 μM), while 5ib from 3-sulfonamido-carbonitrile (3i) was the most significant inhibitor for BChE (IC50 = 1.78 μM). In general, the inhibitory potency of compound 5 was weaker than the pure tacrine reference, and our findings may help to design and develop novel anticholinesterase drugs based on modified tacrines.

Nontargeted screening of veterinary drugs and their metabolites in milk based on mass defect filtering using liquid chromatography-high-resolution mass spectrometry

The development of nontargeted screening strategy for veterinary drugs and their metabolites is very important for food safety. In this study, a nontargeted screening strategy was developed to find the potentially hazardous substances based on mass defect filtering (MDF) using liquid chromatography-high-resolution mass spectrometry. First, the drug metabolites of 112 veterinary drugs from seven classes of antimicrobials were predicted. Second, three MDF models were established, including the traditional rectangular MDF, the enhanced parallelogram MDF, and the polygonal MDF. Finally, the strategy was applied to nontargeted screening of veterinary drugs in 36 milk samples. The polygonal MDF model based on the distribution area of parent drugs and their metabolites showed a better filtering effect. After removing food components and performing MDF, about 10% of the substances remained, and four veterinary drugs and six drug metabolites were discovered and identified, showing the effectiveness of this strategy. The nontargeted screening strategy can rapidly remove interfering substances and find the suspected compounds. It can also be used for nontargeted screening of veterinary drugs and their metabolites in other food matrices.

Therapeutic Potential of Multifunctional Derivatives of Cholinesterase Inhibitors

The aim of this work is to review tacrine analogues from the last three years, which were not included in the latest review work, donepezil and galantamine hybrids from 2015 and rivastigmine derivatives from 2014. In this account, we summarize the efforts toward the development and characterization of non-toxic inhibitors of cholinesterases based on mentioned drugs with various interesting additional properties such as antioxidant, decreasing β-amyloid plaque aggregation, nitric oxide production, pro-inflammatory cytokines release, monoamine oxidase-B activity, cytotoxicity and oxidative stress in vitro and in animal model that classify these hybrids as potential multifunctional therapeutic agents for Alzheimer's disease. Moreover, herein, we have described the cholinergic hypothesis, mechanisms of neurodegeneration and current pharmacotherapy of Alzheimer's disease based on the restoration of cholinergic function through blocking enzymes that break down acetylcholine.

Vitamin B3-Based Biologically Active Compounds as Inhibitors of Human Cholinesterases

We evaluated the potential of nine vitamin B3 scaffold-based derivatives as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors, as a starting point for the development of novel drugs for treating disorders with cholinergic neurotransmission-linked pathology. As the results indicate, all compounds reversibly inhibited both enzymes in the micromolar range pointing to the preference of AChE over BChE for binding the tested derivatives. Molecular docking studies revealed the importance of interactions with AChE active site residues Tyr337 and Tyr124, which dictated most of the observed differences. The most potent inhibitor of both enzymes with K_i of 4 μM for AChE and 8 μM for BChE was the nicotinamide derivative 1-(4′-phenylphenacyl)-3-carbamoylpyridinium bromide. Such a result places it within the range of several currently studied novel cholinesterase inhibitors. Cytotoxicity profiling did not classify this compound as highly toxic, but the induced effects on cells should not be neglected in any future detailed studies and when considering this scaffold for drug development.

Merged Tacrine-Based, Multitarget-Directed Acetylcholinesterase Inhibitors 2015-Present: Synthesis and Biological Activity

Acetylcholinesterase is an important biochemical enzyme in that it controls acetylcholine-mediated neuronal transmission in the central nervous system, contains a unique structure with two binding sites connected by a gorge region, and it has historically been the main pharmacological target for treatment of Alzheimer's disease. Given the large projected increase in Alzheimer's disease cases in the coming decades and its complex, multifactorial nature, new drugs that target multiple aspects of the disease at once are needed. Tacrine, the first acetylcholinesterase inhibitor used clinically but withdrawn due to hepatotoxicity concerns, remains an important starting point in research for the development of multitarget-directed acetylcholinesterase inhibitors. This review highlights tacrine-based, multitarget-directed acetylcholinesterase inhibitors published in the literature since 2015 with a specific focus on merged compounds (i.e., compounds where tacrine and a second pharmacophore show significant overlap in structure). The synthesis of these compounds from readily available starting materials is discussed, along with acetylcholinesterase inhibition data, relative to tacrine, and structure activity relationships. Where applicable, molecular modeling, to elucidate key enzyme-inhibitor interactions, and secondary biological activity is highlighted. Of the numerous compounds identified, there is a subset with promising preliminary screening results, which should inspire further development and future research in this field.

In silico screening of glycogen synthase kinase-3β targeted ligands against acetylcholinesterase and its probable relevance to Alzheimer's disease

Alzheimer's disease (AD) is a growing global health concern that affects 10% of the population aged above 65 years. A growing body of evidence indicates that multi-targeted drugs might be useful therapeutic options owing to the heterogeneity of AD pathology. The current study exploited advanced computational biology tools to identify ligands that might display effective binding to two protein targets in the context of AD. The present study used in silico virtual screening of small molecules library to identify effectiveness against two AD targets viz. acetyl cholinesterase (AChE) and glycogen synthase kinase-3β (GSK-3β). PyRX-Python prescription with AutodockVina was used to generate binding energy profiles. Further screening was accomplished using SwissADME and molecular interaction studies. The present study obtained 48 ligands (absolute binding energy >8 kcal/mol), by virtual screening of 100 ligands. Among those, 13 ligands (BRW, 6VK, 6Z5, SMH, X37, 55E, 65 A, IQ6, 6VL, 6VM, F1B, 6Z2 and GVP) were selected based on blood brain barrier (BBB) permeability, acceptable ADME properties as well as their molecular interaction profiles with the aforementioned AD-targets. The present study has predicted certain molecules that appear worthy to be tested for effectiveness against two AD targets, namely AChE and GSK-3β. However, the results warrant further wet laboratory validation, as computational studies are merely predictive in nature. This approach might be useful for future treatment of AD.Communicated by Ramaswamy H. Sarma.

Synthesis and In Vitro Screening of Novel Heterocyclic β-d-Gluco- and β-d-Galactoconjugates as Butyrylcholinesterase Inhibitors

The development of selective butyrylcholinesterase (BChE) inhibitors may improve the treatment of Alzheimer’s disease by increasing lower synaptic levels of the neurotransmitter acetylcholine, which is hydrolysed by acetylcholinesterase, as well as by overexpressed BChE. An increase in the synaptic levels of acetylcholine leads to normal cholinergic neurotransmission and improved cognitive functions. A series of 14 novel heterocyclic β-d-gluco- and β-d-galactoconjugates were designed and screened for inhibitory activity against BChE. In the kinetic studies, 4 out of 14 compounds showed an inhibitory effect towards BChE, with benzimidazolium and 1-benzylbenzimidazolium substituted β-d-gluco- and β-d-galacto-derivatives in a 10–50 micromolar range. The analysis performed by molecular modelling indicated key residues of the BChE active site, which contributed to a higher affinity toward the selected compounds. Sugar moiety in the inhibitor should enable better blood–brain barrier permeability, and thus increase bioavailability in the central nervous system of these compounds.