New classes of carbazoles as potential multi-functional anti-Alzheimer’s agents

Multi-Target approach is particularly promising way to drug discovery against Alzheimer's disease. In the present study, we synthesized a series of compounds comprising the carbazole backbone linked to the benzyl piperazine, benzyl piperidine, pyridine, quinoline, or isoquinoline moiety through an aliphatic linker and evaluated as cholinesterase inhibitors. The synthesized compounds showed IC₅₀ values of 0.11–36.5 µM and 0.02–98.6 µM against acetyl- and butyrylcholinesterase (AChE and BuChE), respectively. The ligand-protein docking simulations and kinetic studies revealed that compound 3s could bind effectively to the peripheral anionic binding site (PAS) and anionic site of the enzyme with mixed-type inhibition. Compound 3s was the most potent compound against AChE and BuChE and showed acceptable inhibition potency for self- and AChE-induced Aβ_1-42 aggregation. Moreover, compound 3s could significantly protect PC12 cells against H₂O₂-induced toxicity. The results suggested that the compounds 3s could be considered as a promising multi-functional agent for further drug discovery development against Alzheimer's disease.     

Novel isosorbide di-ester compounds as inhibitors of acetylcholinesterase

We report herein that a variety of isosorbide di-esters, previously reported to be novel substrates for butyrylcholinesterase (BuChE, EC 3.1.1.8), are in fact inhibitors of the homologous enzyme acetylcholinesterase (AChE), with IC(50) values in the micromolar range. In vitro studies show that they are mixed inhibitors of the enzyme, and thus the ternary enzyme-inhibitor-substrate complex can form in acetylcholinesterase. This is rationalised by molecular modelling which shows that the compounds bind in the mid-gorge area. In this position, simultaneous substrate binding might be possible, but the hydrolysis of this substrate is prevented. The di-esters dock within the butyrylcholinesterase gorge in a very different manner, with the ester sidechain at the 5-position occupying the acyl pocket at residues Leu286 and Val288, and the 2-ester binding to Trp82. The carbonyl group of the 2-ester is susceptible to nucleophilic attack by Ser198 of the catalytic triad. The larger residues of the acyl pocket in acetylcholinesterase prevent binding in this manner. The results complement each other and explain the differing behaviours of the esters in the cholinesterase enzymes. These findings may prove very significant for future work.     

New benzyl pyridinium derivatives bearing 2,4-dioxochroman moiety as potent agents for treatment of Alzheimer’s disease: Design,synthesis, biological evaluation,and docking study

A new series of benzyl pyridinium-2,4-dioxochroman derivatives 7a-o was synthesized and evaluated as new anti-Alzheimer agents. Among the synthesized compounds, the compounds 7f and 7i exhibited the most potent anti-AChE and anti-BuChE activities, respectively. The kinetic study of the compound 7f revealed that this compound inhibited AChE in a mixed-type inhibition mode. Furthermore, the docking study of the compounds 7f and 7i showed that these compounds bound to both the catalytic site (CS) and peripheral anionic site (PAS) of AChE and BuChE, respectively. The compound 7f also exhibited a greater self-induced Aβ peptide aggregation inhibitory activity in compare to donepezil. Furthermore, the neuroprotective activity of this compound at 20 μM was comparable to that of the standard neuroprotective agent (quercetin).     

Discovery of potent and selective butyrylcholinesterase inhibitors through the use of pharmacophore-based screening

Cholinesterase inhibitors have long been used in the treatment of Alzheimer’s Disease (AD) via the protection of acetylcholine levels. However, recent research has shown that the specific inhibition of butyrylcholinesterase (BChE) could better ameliorate symptoms within patients. In addition, it has recently been shown that selective inhibition of BChE can also significantly attenuate the toxicity and physiological effects of heroin. Currently, there are no specific and potent inhibitors of BChE approved for use in AD or heroin abuse. Through a combined use of in silico and in vitro screening, we have found three compounds with sub-50 nM IC₅₀ values that specifically target BChE. These newly discovered BChE inhibitors can act as the lead scaffolds for future development of the desirably potent and selective BChE inhibitors.     

Design,synthesis, and multitargeted profiling of N-benzylpyrrolidine derivatives for the treatment of Alzheimer’s disease

Multitarget molecular hybrids of N-benzyl pyrrolidine derivatives were designed, synthesized, and biologically evaluated for the treatment of Alzheimer’s disease (AD). Among the synthesized compounds, 4k and 4o showed balanced enzyme inhibitions against cholinesterases (AChE and BChE) and BACE-1. Both leads showed considerable PAS-AChE binding capability, excellent brain permeation, potential disassembly of Aβ aggregates, and neuroprotective activity against Aβ-induced stress. Compounds 4k and 4o also ameliorated cognitive dysfunction against the scopolamine-induced amnesia model in the Y-maze test. The ex vivo study signified attenuated brain AChE activity and antioxidant potential of compounds 4k and 4o. Furthermore, compound 4o also showed improvement in Aβ-induced cognitive dysfunction by the Morris water maze test with excellent oral absorption characteristics ascertained by the pharmacokinetic study. In silico molecular docking and dynamics simulation studies of leads suggested their consensual binding affinity toward PAS-AChE in addition to aspartate dyad of BACE-1.     

Structure–activity relationship study of BACE1 inhibitors possessing a chelidonic or 2,6-pyridinedicarboxylic scaffold at the P2 position

We have previously reported potent substrate-based pentapeptidic BACE1 inhibitors possessing a hydroxymethylcarbonyl isostere as a substrate transition-state mimic. While these inhibitors exhibited potent activities in enzymatic and cellular assays (KMI-429 in particular inhibited Aβ production in vivo), these inhibitors contained some natural amino acids that seemed to be required to improve enzymatic stability in vivo and permeability across the blood–brain barrier, so as to be practical drug. Recently, we synthesized non-peptidic and small-sized BACE1 inhibitors possessing a heterocyclic scaffold at the P₂ position. Herein we report the SAR study of BACE1 inhibitors possessing this heterocyclic scaffold, a chelidonic or 2,6-pyridinedicarboxylic moiety.     

Design,synthesis and anti-Alzheimer’s activity of novel 1,2,3-triazole-chromenone carboxamide derivatives

Alzheimer’s disease (AD) is a well-known neurodegenerative disorder affecting millions of old people worldwide and the corresponding epidemiological data highlights the significance of the disease. As AD is a multifactorial illness, various single-target directed drugs that have reached clinical trials have failed. Therefore, various factors associated with outset of AD have been considered in targeted drug discovery and development. In this work, a wide range of 1,2,3-triazole-chromenone carboxamides were designed, synthesized, and evaluated for their cholinesterase inhibitory activity. Among them, N-(1-benzylpiperidin-4-yl)-7-((1-(3,4-dimethylbenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-2-oxo-2H-chromene-3-carboxamide (11b) showed the best acetylcholinesterase inhibitory activity (IC₅₀ = 1.80 µM), however, it was inactive toward butyrylcholinesterase. It should be noted that compound 11b was evaluated for its BACE1 inhibitory activity and calculated IC₅₀ = 21.13 µM confirmed desired inhibitory activity. Also, this compound revealed satisfactory neuroprotective effect against H₂O₂-induced cell death in PC12 neurons at 50 µM as well as metal chelating ability toward Fe²⁺, Cu²⁺, and Zn²⁺ ions.     

Novel multi-target compounds in the quest for new chemotherapies against Alzheimer’s disease: An experimental and theoretical study

The lack of any effective therapy along with the aging world population anticipates a growth of the worldwide incidence of Alzheimer’s disease (AD) to more than 100 million cases by 2050. Accumulation of extracellular amyloid-β (Aβ) plaques, intracellular tangles in the brain, and formation of reactive oxygen species (ROS) are the major hallmarks of the disease. In the amyloidogenic process, a β-secretase, known as BACE 1, plays a fundamental role in the production of Aβ fragments, and therefore, inhibition of such enzymes represents a major strategy for the rational design of anti-AD drugs. In this work, a series of four multi-target compounds (1–4), inspired by previously described ionophoric polyphenols, have been synthesized and studied. These compounds have been designed to target important aspects of AD, including BACE 1 enzymatic activity, Aβ aggregation, toxic concentrations of Cu²⁺ metal ions and/or ROS production. Two other compounds (5 and 6), previously reported by some of us as antimalarial agents, have also been studied because of their potential as multi-target species against AD. Interestingly, compounds 3 and 5 showed moderate to good ability to inhibit BACE 1 enzymatic activity in a FRET assay, with IC₅₀′s in the low micromolar range (4.4?±?0.3 and 1.7?±?0.3?μM, respectively), comparable to other multi-target species, and showing that the observed activity was in part due to a competitive binding of the compounds at the active site of the enzyme. Theoretical docking calculations overall agreed with FRET assay results, displaying the strongest binding affinities for 3 and 5 at the active site of the enzyme. In addition, all compounds selectively interacted with Cu²⁺ metal ions forming 2:1 complexes, inhibited the production of Aβ-Cu²⁺ catalyzed hydroxyl radicals up to a ～100% extent, and scavenged AAPH-induced peroxyl radical species comparably to resveratrol, a compound used as reference in this work. Our results also show good anti-amyloidogenic ability: compounds 1–6 inhibited both the Cu²⁺-induced and self-induced Aβ(1–40) fibril aggregation to an extent that ranged from 31% to 77%, while they disaggregated pre-formed Aβ(1–40) mature fibrils up to a 37% and a 69% extent in absence and presence of Cu²⁺, respectively. Cytotoxicity was additionally studied in Tetrahymena thermophila and HEK293 cells, and compared to that of resveratrol, showing that compounds 1–6 display lower toxicity than that of resveratrol, a well-known non-toxic polyphenol.     

Design,synthesis, in vitro,and in silico studies of novel diarylimidazole-1,2,3-triazole hybrids as potent α-glucosidase inhibitors

In this work, new derivatives of diarylimidazole-1,2,3-triazole 7a-p were designed, synthesized, and evaluated for their in vitro α-glucosidase inhibitory activity. All compounds showed potent inhibitory activity in the range of IC₅₀ = 90.4–246.7 µM comparing with acarbose as the standard drug (IC₅₀ = 750.0 µM). Among the synthesized compounds, compounds 7b, 7c, and 7e were approximately 8 times more potent than acarbose. The kinetic study of those compounds indicated that they acted as the competitive inhibitors of α-glucosidase. Molecular docking studies were also carried out for compounds 7b, 7c, and 7e using modeled α-glucosidase to find the interaction modes responsible for the desired inhibitory activity.     

利用受体漂白荧光共振能量转移技术研究β-分泌酶在活细胞内的二聚化

β淀粉样肽(Aβ)在阿尔茨海默病(AD)患者脑内的产生、聚集和沉积是AD的一个固有病理特征,也被普遍认为是AD的重要发病机理之一.β-分泌酶(BACE)对淀粉样前体蛋白(APP)的裂解是Aβ产生的关键步骤,β-分泌酶抑制剂是AD药物治疗的一个重要发展方向,因此对BACE结构的了解具有重要意义.利用受体漂白荧光共振能量转移(FRET)技术首次在活细胞内研究BACE的二聚化结构.通过基因工程技术分别构建了青色荧光蛋白(CFP)和黄色荧光蛋白(YFP)标记的全长BACE(BACE-FL)和BACE活性部分(BACE-NT),应用共聚焦荧光显微镜和受体漂白FRET技术研究了BACE-FL和BACE-NT在细胞中的表达和定位,以及它们在活细胞内的存在形式.实验结果表明:a.BACE-FL在内质网至细胞膜均有表达,主要分布在高尔基体、细胞膜和内体等细胞器中,而BACE-NT则被滞留在内质网里.b.BACE-NT是单体结构,而BACE-FL在活细胞内则以二聚体的形式存在.证明,BACE的跨膜序列和C端对BACE的转运和定位具有重要作用,其二聚体结构由这些序列决定,而不由其活性位点决定.