Design,synthesis and evaluation of flavonoid derivatives as potential multifunctional acetylcholinesterase inhibitors against Alzheimer’s disease

A new series of flavonoid derivatives were designed, synthesized and evaluated as potential multifunctional AChE inhibitors against Alzheimer’s disease. Most of them exhibited potent AChE inhibitory activity, high selectivity for AChE over BuChE, and moderate to good inhibitory potency toward Aβ aggregation. Specifically, compound 12c was the strongest AChE inhibitor, being 20-fold more potent than galanthamine and twofold more potent than tacrine, and it also had ability to inhibit Aβ aggregation (close to the reference compound) and to function as a metal chelator. Molecular modeling and enzyme kinetic study revealed that it targeted both the catalytic active site and the peripheral anionic site of AChE. Consequently, this class of compounds deserved to be thoroughly and systematically studied for the treatment of Alzheimer’s disease.     

Tacrine–propargylamine derivatives with improved acetylcholinesterase inhibitory activity and lower hepatotoxicity as a potential lead compound for the treatment of Alzheimer’s disease

Abstract

A series of tacrine–propargylamine derivatives were synthesised and evaluated as possible anti-Alzheimer’s disease (AD) agents. Among these derivatives, compounds 3a and 3b exhibited superior activities and a favourable balance of AChE and BuChE activities (3a: IC₅₀ values of 51.3 and 77.6?nM; 3b: IC₅₀ values of 11.2 and 83.5?nM). Compounds 3a and 3b also exhibited increased hAChE inhibitory activity compared with tacrine by approximately 5- and 28-fold, respectively, and low neurotoxicity. Importantly, these compounds also had lower hepatotoxicity than tacrine. Based on these results, compounds 3a and 3b could be considered as potential lead compounds for the treatment of AD and other AChE related diseases, such as schizophrenia, glaucoma and myasthenia gravis.     

Synthesis and in vitro evaluation of vanillin derivatives as multi-target therapeutics for the treatment of Alzheimer’s disease

A number of novel naphthalimido and phthalimido vanillin derivatives were synthesised, and evaluated as antioxidants and cholinesterase inhibitors in vitro. Antioxidant activity was assessed using DPPH, FRAP, and ORAC assays. All compounds demonstrated enhanced activity compared to the parent compound, vanillin. They also exhibited BuChE selectivity in Ellman’s assay. A lead compound, 2a (2-(3-(bis(4-hydroxy-3-methoxybenzyl)amino)propyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione), was identified and displayed strong antioxidant activity (IC₅₀ of 16.67 µM in the DPPH assay, a 25-fold increase in activity compared to vanillin in the FRAP assay, and 9.43 TE in the ORAC assay). Furthermore, 2a exhibited potent BuChE selectivity, with an IC₅₀ of 0.27 µM which was around 53-fold greater than the corresponding AChE inhibitory activity. Molecular modelling studies showed that molecules with bulkier groups, as in 2a, exhibited better BuChE selectivity. This work provides a promising basis for the development of multi-target hybrid compounds based on vanillin as potential AD therapeutics.     

Synthesis,biological evaluation and molecular dynamic simulations of novel Benzofuran-tetrazole derivatives as potential agents against Alzheimer’s disease

A series of novel Benzofuran-tetrazole derivatives were successfully synthesised by integrating multicomponent Ugi-azide reaction with the molecular hybridization approach. Interestingly, a number of synthesized derivatives (5c, 5d, 5i, 5l, 5q and 5s) exhibited significant reduction of aggregation of “human” amyloid beta peptide, expressing on transgenic Caenorhabditis elegans (C. elegans) strain CL4176. Further, in silico docking results have evidenced the exquisite interaction of active compounds with the help of TcAChE–E2020 complex. These findings underscore the potential of these hybrids as lead molecules against Alzheimers’s disease.     

Lead optimization studies towards the discovery of novel carbamates as potent AChE inhibitors for the potential treatment of Alzheimer’s disease

The optimization of our previous lead compound 1 (AChE IC₅₀ = 3.31 μM) through synthesis and pharmacology of a series of novel carbamates is reported. The synthesized compounds were evaluated against mouse brain AChE enzyme using the colorimetric method described by Ellman et al. The three compounds 6a (IC₅₀ = 2.57 μM), 6b (IC₅₀ = 0.70 μM) and 6i (IC₅₀ = 2.56 μM) exhibited potent in vitro AChE inhibitory activities comparable to the drug rivastigmine (IC₅₀ = 1.11 μM). Among them, the compound 6b has been selected as possible optimized lead for further neuropharmacological studies. In addition, the AChE–carbamate Michaelis complexes of these potent compounds including rivastigmine and ganstigmine have been modeled using covalent docking protocol of GOLD and important direct/indirect interactions contributing to stabilization of the AChE–carbamate Michaelis complexes have been investigated.     

Design and development of novel p-aminobenzoic acid derivatives as potential cholinesterase inhibitors for the treatment of Alzheimer’s disease

Based on the quantitative structure-activity relationship (QSAR), some novel p-aminobenzoic acid derivatives as promising cholinesterase enzyme inhibitors were designed, synthesized, characterized and evaluated to enhance learning and memory. The in vitro enzyme kinetic study of the synthesized compounds revealed the type of inhibition on the respective acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vivo studies of the synthesized compounds exhibited significant reversal of cognitive deficits in the animal models of amnesia as compared to standard drug donepezil. Further, the ex vivo studies in the specific brain regions like the hippocampus, hypothalamus, and prefrontal cortex regions also exhibited AChE inhibition comparable to standard donepezil. The in silico molecular docking and dynamics simulations studies of the most potent compound 22 revealed the consensual interactions at the active site pocket of the AChE.     

Design,synthesis and evaluation of 4′-OH-flurbiprofen-chalcone hybrids as potential multifunctional agents for Alzheimer’s disease treatment

A series of 4′-OH-flurbiprofen-chalcone hybrids were designed, synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease. The biological screening results indicated that most of these hybrids exhibited good multifunctional activities. Among them, compounds 7k and 7m demonstrated the best inhibitory effects on self-induced Aβ_1–42 aggregation (60.0% and 78.2%, respectively) and Cu²⁺-induced Aβ_1–42 aggregation (52.4% and 95.0%, respectively). Moreover, these two representative compounds also exhibited good antioxidant activities, MAO inhibitions, biometal chelating abilities and anti-neuroinflammatory activities in vitro. Furthermore, compound 7m displayed appropriate blood-brain barrier permeability. These multifunctional properties highlight compound 7k and 7m as promising candidates for further development of multi-functional drugs against AD.     

Search for multifunctional agents against Alzheimer’s disease among non-imidazole histamine H3 receptor ligands. In vitro and in vivo pharmacological evaluation and computational studies of piperazine derivatives

In the search for new treatments for complex disorders such as Alzheimer’s disease the Multi-Target-Directed Ligands represent a very promising approach. The aim of the present study was to identify multifunctional compounds among several series of non-imidazole histamine H3 receptor ligands, derivatives of 1-[2-thiazol-5-yl-(2-aminoethyl)]-4-n-propylpiperazine, 1-[2-thiazol-4-yl-(2-aminoethyl)]-4-n-propylpiperazine and 1-phenoxyalkyl-4-(amino)alkylopiperazine using in vitro and in vivo pharmacological evaluation and computational studies. Performed in vitro assays showed moderate potency of tested compounds against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Molecular modeling studies have revealed possible interactions between the active compounds and both AChE and BuChE as well as the human H3 histamine receptor. Computational studies showed the high drug-likeness of selected compounds with very good physicochemical profiles. The parallel artificial membrane permeation assay proved outstanding blood–brain barrier penetration in test conditions. The most promising compound, A12, chemically methyl(4-phenylbutyl){2-[2-(4-propylpiperazin-1-yl)-1,3-thiazol-5-yl]ethyl}amine, possesses good balanced multifunctional profile with potency toward studied targets - H3 antagonist activity (pA₂ = 8.27), inhibitory activity against both AChE (IC₅₀ = 13.96 μM), and BuChE (IC₅₀ = 14.62 μM). The in vivo pharmacological studies revealed the anti-amnestic properties of compound A12 in the passive avoidance test on mice.     

In vivo ROS production and use of oxidative stress-derived biomarkers to detect the onset of diseases such as Alzheimer’s disease,Parkinson’s disease,and diabetes

Breakthroughs in biochemistry have furthered our understanding of the onset and progression of various diseases, and have advanced the development of new therapeutics. Oxidative stress and reactive oxygen species (ROS) are ubiquitous in biological systems. ROS can be formed non-enzymatically by chemical, photochemical and electron transfer reactions, or as the byproducts of endogenous enzymatic reactions, phagocytosis, and inflammation. Imbalances in ROS homeostasis, caused by impairments in antioxidant enzymes or non-enzymatic antioxidant networks, increase oxidative stress, leading to the deleterious oxidation and chemical modification of biomacromolecules such as lipids, DNA, and proteins. While many ROS are intracellular signaling messengers and most products of oxidative metabolisms are beneficial for normal cellular function, the elevation of ROS levels by light, hyperglycemia, peroxisomes, and certain enzymes causes oxidative stress-sensitive signaling, toxicity, oncogenesis, neurodegenerative diseases, and diabetes. Although the underlying mechanisms of these diseases are manifold, oxidative stress caused by ROS is a major contributing factor in their onset. This review summarizes the relationship between ROS and oxidative stress, with special reference to recent advancements in the detection of biomarkers related to oxidative stress. Further, we will introduce biomarkers for the early detection of neurodegenerative diseases and diabetes, with a focus on our recent work.     

Design,synthesis and evaluation of chalcone Mannich base derivatives as multifunctional agents for the potential treatment of Alzheimer’s disease

A series of chalcone Mannich base derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer’s disease based on the multi-target directed ligands design strategy. In vitro assays demonstrated that most of the derivatives exerted potent selective inhibitory potency on AChE with good multifunctional properties. Among them, representative compound 7c exhibited moderate inhibitory potency for EeAChE (IC₅₀ = 0.44 μM) and MAO-B inhibition (IC₅₀ = 1.21 μM), good inhibitory effect on self-induced Aβ₁₋₄₂ aggregation (55.0%, at 25 μM), biometal chelating property, moderate antioxidant activity with a value 1.93-fold of Trolox. Moreover, both kinetic analysis of AChE inhibition and molecular modeling study revealed that 7c showed a mixed-type inhibition, binding simultaneously to CAS and PAS of AChE. In addition, 7c also displayed high BBB permeability. These properties indicated 7c may be a promising multifunctional agent for the treatment of AD.     

Chlorinated tacrine analogs: Design,synthesis and biological evaluation of their anti-cholinesterase activity as potential treatment for Alzheimer’s disease

In search of potent acetyl cholinesterase inhibitors with low hepatotoxicity for the treatment of Alzheimer’s disease, introduction of a chloro substitution to tacrine and some of its analogs has proven to be beneficial in maintaining or potentiating the cholinesterase inhibitory activity. Furthermore, it was found to be able to reduce the hepatotoxicity of the synthesized compounds, which is the main target of the study. Accordingly, a series of new 4-(chlorophenyl)tetrahydroquinoline derivatives, was synthesized and characterized. The synthesized compounds were evaluated for their in vitro and in vivo anti-cholinesterase activity using tacrine as a reference standard. Furthermore, they were investigated for their hepatotoxicity compared to tacrine. The obtained biological results revealed that all synthesized compounds displayed equivalent or significantly higher anti-cholinesterase activity and lower hepatotoxicity in comparison to tacrine. In addition, in silico drug-likeness of the synthesized compounds were predicted and their practical logP were assessed indicating that all synthesized compounds can be considered as promising hits/leads. Furthermore, docking study of the compound showing the highest in vitro anticholinesterase activity was performed and its binding mode was compared to that of tacrine.     

Cholinesterase inhibitory activity of tinosporide and 8-hydroxytinosporide isolated from Tinospora cordifolia: In vitro and in silico studies targeting management of Alzheimer’s disease

Tinosporide and 8-hydroxytinosporide isolated from Tinospora cordifolia were evaluated for acetylcholinesterase (AChE) and butylcholinesterase (BuChE) inhibitory activities. The structure of the compound was confirmed by spectroscopic analysis, whereas cholinesterase inhibition was investigated by Ellman method using donepezil as standard drug and the data were presented as IC₅₀ (μg/ml ± SEM). Furthermore, donepezil, tinosporide and 8-hydroxytinosporide were executed for docking analysis. The results from the isolated compounds TC-16R confirmed as tinosporide promisingly inhibited AChE with IC₅₀ value of 13.45 ± 0.144, whereas TC-19R confirmed as 8-hydroxytinosporide moderately inhibited AChE with IC₅₀ value of 46.71 ± 0.511. In case of BuChE inhibition, the IC₅₀ values were found to be 408.50 ± 17.197 and 317.26 ± 6.918 for tinosporide and 8-hydroxytinosporide, respectively. The in silico studies revealed that the ligand tinosporide fit with the binding sites and inhibited AChE. Overall, the study findings suggested that tinosporide would be a complementary noble molecule of donepezil which is correlated with its pharmacological activity through in vitro studies, while 8-hydroxytinosporide modestly inhibited BuChE and the results are very close to the standard donepezil.     

Design,synthesis, in vitro and in vivo evaluation of benzylpiperidine-linked 1,3-dimethylbenzimidazolinones as cholinesterase inhibitors against Alzheimer’s disease

Abstract

Cholinesterase inhibitor plays an important role in the treatment of patients with Alzheimer’s disease (AD). Herein, we report the medicinal chemistry efforts leading to a new series of 1,3-dimethylbenzimidazolinone derivatives. Among the synthesised compounds, 15b and 15j showed submicromolar IC₅₀ values (15b, eeAChE IC₅₀?=?0.39?±?0.11?µM; 15j, eqBChE IC₅₀?=?0.16?±?0.04?µM) towards acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Kinetic and molecular modelling studies revealed that 15b and 15j act in a competitive manner. 15b and 15j showed neuroprotective effect against H₂O₂-induced oxidative damage on PC12 cells. This effect was further supported by their antioxidant activity determined in a DPPH assay in vitro. Morris water maze test confirmed the memory amelioration effect of the two compounds in a scopolamine-induced mouse model. Moreover, the hepatotoxicity of 15b and 15j was lower than tacrine. In summary, these data suggest 15b and 15j are promising multifunctional agents against AD.     

Acylhydrazones as isoniazid derivatives with multi-target profiles for the treatment of Alzheimer’s disease: Radical scavenging,myeloperoxidase/acetylcholinesterase inhibition and biometal chelation

Acylhydrazones 1a-o, derived from isoniazid, were synthesized and evaluated for Myeloperoxidase (MPO) and Acetylcholinesterase (AChE) inhibition, as well as their antioxidant and metal chelating activities, with the purpose of investigating potential multi-target profiles for the treatment of Alzheimer’s disease. Synthesized compounds were tested using the 2,2-diphenyl-2-picrylhydrazyl (DPPH) method and 1i, 1j and 1 m showed radical scavenging ability. Compounds 1b, 1 h, 1i, 1 m and 1o inhibited MPO activity (10 μM) at 96.1 ± 5.5%, 90 ± 2.1%, 100.3 ± 1.7%, 80.1 ± 9.4% and 82.2 ± 10.6%, respectively, and only compound 1 m was able to inhibit 54.2 ± 1.7% of AChE activity (100 μM). Docking studies of the most potent compound 1 m were carried out, and the computational results provided the theoretical basis of enzyme inhibition. Furthermore, compound 1 m was able to form complexes with Fe²⁺ and Zn²⁺ ions in a 2:1 ligand:metal ratio according to the Job Plot method.     

A new target for Alzheimer’s disease: A small molecule SERCA activator is neuroprotective in vitro and improves memory and cognition in APP/PS1 mice

Amongst the cellular cacophony of altered signals in Alzheimer’s disease (AD), disrupted Ca²⁺ homeostasis and consequential endoplasmic reticulum (ER) stress signals have been recognized as key determinants of neuron fate. This altered Ca²⁺ state is accompanied by a failing sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) pump, which has been recognized as a causal feature of the underlying disease state. Repair of the Ca²⁺ dyshomeostasis represents a putative drug target via alleviation of ER stress and rescue of injured neurons, effectively modifying the AD state. Herein, we report a small molecule SERCA activator that rescues brain cells and raises ER Ca²⁺ in vitro, and shows efficacy in the APP/PS1 double transgenic mouse model of Alzheimer’s disease. These results support SERCA activation as a therapeutic target for AD.