Synthesis and inhibitory activity of ureidophosphonates,against acetylcholinesterase: Pharmacological assay and molecular modeling

A novel method has been developed for the synthesis of 1-ureidophosphonates through a three components condensation of aldehyde with amine and diethylphosphite in the presence of sulfanilic acid as catalyst followed by subsequent reaction of the product with isocyanate. This method is easy, rapid, and good yielding. The anticholinesterase (AChE) activities (inhibition potency through IC₅₀) of newly synthesized 1-ureidophosphonates were also investigated. The activities of the synthesized compounds toward the enzyme AChE were determined and compared in terms of their molecular structures and it was found, through molecular docking simulations, that the most potent derivative (compound 3i) inhibited the enzyme through binding to the peripheral anionic site (PAS) and not to its acylation site (A site).     

Synthesis, aggregation, and neurotoxicity of the Alzheimer's Abeta1-42 amyloid peptide and its isoaspartyl isomers

Amyloid Abeta1-42 peptide (Abeta1-42) and its isomers with an isoaspartyl residue at position 7 or 23 [Abeta1-42(isoAsp7) and Abeta1-42(isoAsp23)] were synthesized in high purity by the Fmoc-solid phase technique, followed by HPLC on a silica-based reversed-phase column under the basic conditions. Importantly, Abeta1-42(isoAsp23) aggregated more strongly than native Abeta1-42 and showed significant neurotoxicity, while the aggregation ability and neurotoxicity of Abeta1-42(isoAsp7) was weak. This suggests that the isomerization of the aspartyl residues plays an important role in fibril formation in Alzheimer's disease.     

Synthesis,biological evaluation and molecular modeling of aloe-emodin derivatives as new acetylcholinesterase inhibitors

A series of aloe-emodin derivatives were designed, synthesized and evaluated as acetylcholinesterase inhibitors. Most of the new prepared compounds showed remarkable acetylcholinesterase inhibitory activities. Among them, the compound 1-((4,5-dihydroxy-9,10-dioxo-9,10-dihydroanthracen-2-yl) methyl) pyridin-1-ium chloride (C3) which has a pyridinium substituent possessed the best inhibitory activity of acetylcholinesterase (IC₅₀ = 0.09 μM). The docking study performed with AUTODOCK demonstrated that C3 could interact with the catalytic active site (CAS) and the peripheral anionic site (PAS) of acetylcholinesterase.     

Protective effect of quercetin in primary neurons against Abeta(1-42): relevance to Alzheimer's disease

Quercetin, a flavonoid found in various foodstuffs, has antioxidant properties and increases glutathione (GSH) levels and antioxidant enzyme function. Considerable attention has been focused on increasing the intracellular GSH levels in many diseases, including Alzheimer's disease (AD). Amyloid beta-peptide [Abeta(1-42)], elevated in AD brain, is associated with oxidative stress and neurotoxicity. We aimed to investigate the protective effects of quercetin on Abeta(1-42)-induced oxidative cell toxicity in cultured neurons in the present study. Decreased cell survival in neuronal cultures treated with Abeta(1-42) correlated with increased free radical production measured by dichlorofluorescein fluorescence and an increase in protein oxidation (protein carbonyl, 3-nitrotyrosine) and lipid peroxidation (protein-bound 4-hydroxy-2-nonenal). Pretreatment of primary hippocampal cultures with quercetin significantly attenuated Abeta(1-42)-induced cytotoxicity, protein oxidation, lipid peroxidation and apoptosis. A dose-response study suggested that quercetin showed protective effects against Abeta(1-42) toxicity by modulating oxidative stress at lower doses, but higher doses were not only non-neuroprotective but also toxic. These findings provide motivation to test the hypothesis that quercetin may provide a promising approach for the treatment of AD and other oxidative-stress-related neurodegenerative diseases.     

Synthesis,biological activity and molecular modeling studies on 1H-benzimidazole derivatives as acetylcholinesterase inhibitors

A series of N-{2-[4-(1H-benzimidazole-2-yl)phenoxy]ethyl}substituted amine derivatives were designed to assess cholinesterase inhibitor activities. Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitor activities were evaluated in vitro by using Ellman’s method. It was discovered that most of the compounds displayed AChE and/or BuChE inhibitor activity and few compounds were selective against AChE/BuChE. Compound 3c and 3e were the most active compounds in the series against eeAChE and hAChE, respectively. Molecular docking studies and molecular dynamics simulations were also carried out.     

Plasma beta carotene in Alzheimer's disease. Association with cerebrospinal fluid beta-amyloid 1-40, (Abeta40), beta-amyloid 1-42 (Abeta42) and total Tau

We studied the plasma beta carotene concentrations in 40 Alzheimer's disease patients and the association with cerebrospinal fluid beta-amyloid 1-40, (Abeta40), cerebrospinal fluid beta-amyloid 1-42 (Abeta42) and cerebrospinal fluid total Tau. We found that patients with plasma beta carotene levels below the 25th percentile had 55% reduced ratios of Abeta40/Tau and 51% reduced ratios of Abeta 40/Abeta 42 compared with patients in the highest quartile. Mean Tau concentrations in the lowest quartile of plasma beta-carotene levels were 74% higher compared with the highest quartile of plasma beta-carotene levels. Thus, we could demonstrate an statistically significant association between beta carotene levels in plasma and neurochemical markers in the cerebrospinal fluid of Alzheimer's disease patients.     

Synthesis,molecular docking,acetylcholinesterase and butyrylcholinesterase inhibitory potential of thiazole analogs as new inhibitors for Alzheimer disease

A series of thirty (30) thiazole analogs were prepared, characterized by ¹H NMR, ¹³C NMR and EI-MS and evaluated for Acetylcholinesterase and butyrylcholinesterase inhibitory potential. All analogs exhibited varied butyrylcholinesterase inhibitory activity with IC₅₀ value ranging between 1.59 ± 0.01 and 389.25 ± 1.75 μM when compared with the standard eserine (IC₅₀, 0.85 ± 0.0001 μM). Analogs 15, 7, 12, 9, 14, 1, 30 with IC₅₀ values 1.59 ± 0.01, 1.77 ± 0.01, 6.21 ± 0.01, 7.56 ± 0.01, 8.46 ± 0.01, 14.81 ± 0.32 and 16.54 ± 0.21 μM respectively showed excellent inhibitory potential. Seven analogs 15, 20, 19, 24, 28, 30 and 25 exhibited good acetylcholinesterase inhibitory potential with IC50 values 21.3 ± 0.50, 35.3 ± 0.64, 36.6 ± 0.70, 44.81 ± 0.81, 46.36 ± 0.84, 48.2 ± 0.06 and 48.72 ± 0.91 μM respectively. All other analogs also exhibited well to moderate enzyme inhibition. The binding mode of these compounds was confirmed through molecular docking.     

Design,synthesis and evaluation of phthalide alkyl tertiary amine derivatives as promising acetylcholinesterase inhibitors with high potency and selectivity against Alzheimer's disease

A series of phthalide alkyl tertiary amine derivatives were designed, synthesized and evaluated as potential multi-target agents against Alzheimer’s disease (AD). The results indicated that almost all the compounds displayed significant AChE inhibitory and selective activities. Besides, most of the derivatives exhibited increased self-induced Aβ_1-42 aggregation inhibitory activity compared to the lead compound dl-NBP, and some compounds also exerted good antioxidant activity. Specifically, compound I-8 showed the highest inhibitory potency toward AChE (IC₅₀ = 2.66 nM), which was significantly better than Donepezil (IC₅₀ = 26.4 nM). Moreover, molecular docking studies revealed that compound I-8 could bind to both the catalytic active site and peripheral anionic site of AChE. Furthermore, compound I-8 displayed excellent BBB permeability in vitro. Importantly, the step-down passive avoidance test indicated that I-8 significantly reversed scopolamine-induced memory deficit in mice. Collectively, these results suggested that I-8 might be a potent and selective AChE inhibitor for further anti-AD drug development.     

Synthesis,molecular modeling and BACE-1 inhibitory study of tetrahydrobenzo[b] pyran derivatives

β-Secretase (BACE1) has been broadly documented as one of the possible therapeutic targets for the treatment of Alzheimer’s disease. In this paper, we report the synthesis and the for β-secretase (BACE-1) inhibitory activity of new series of tetrahydrobenzo [b] pyran derivatives. One-pot synthesis of tetrahydrobenzo [b] pyrans was carried out by condensing aromatic aldehyde, malononitrile and 1,3-cyclohexanedione using ionic liquid 1-butyl-3-methyl imidazolium chloride ([bmIm]Cl⁻) in aqueous alcohol media. The addition of alcohol and water in the ratio of 1:2 keeps all the reactants in solution which facilitates the reaction and makes the product formation very easy. The synthesized compounds were subjected to BACE1 inhibition assay and six compounds, 4d, 4e, 4f, 4h, 4i, and 4p have shown significant IC₅₀ values at micromolar level. Among these six active compounds, 4e was a potential inhibitor with its IC₅₀ value in nanomolar range. All the synthesized compounds were docked onto the active site of β-Secretase enzyme.     

Synthesis,biological evaluation,and molecular modeling of berberine derivatives as potent acetylcholinesterase inhibitors

By targeting the dual active sites of acetylcholinesterase (AChE), a new series of berberine derivatives was designed, synthesized, and evaluated as AChE inhibitors. Most of the derivatives inhibited AChE in the sub-micromolar range. Compound 8c, berberine linked with phenol by a 4-carbon spacer, showed the most potent inhibition of AChE. A kinetic study of AChE and BuChE indicated that a mix-competitive binding mode existed for these berberine derivatives. Molecular modeling studies confirmed that these hybrids target both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. This is the first report where AChE inhibitory activity has been associated with berberine as a lead molecule.     

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.     

Synthesis,aggregation, neurotoxicity,and secondary structure of various A beta 1-42 mutants of familial Alzheimer's disease at positions 21-23

Cerebral amyloid angiopathy (CAA) due to amyloid beta (A beta) deposition is a key pathological feature of Alzheimer's disease (AD), especially in some form of familial Alzheimer's disease (FAD) including hereditary cerebral hemorrhage with amyloidosis-Dutch type. A beta mainly consists of 40- and 42-mer peptides (Abeta 1-40 and A beta 1-42), which accumulate in senile plaques of AD brains and show neurotoxicity for cultured nerve cells. We synthesized all variant forms of A beta 1-42 associated with reported FAD, such as A21G (Flemish), E22Q (Dutch), E22K (Italian), E22G (Arctic), and D23N (Iowa) along with three potential mutants by one point missense mutation (E22A, E22D, and E22V) in a highly pure form, and examined their ability to aggregate and their neurotoxicity in PC12 cells. The mutants at positions 22 and 23 showed potent aggregative ability and neurotoxicity whereas the potential mutants did not, indicating that A beta 1-42 mutants at positions 22 and 23 play a critical role in FAD of Dutch-, Italian-, Arctic-, and Iowa-types. However, Flemish-type FAD needs alternative explanation except the aggregation and neurotoxicity of the corresponding A beta 1-42 mutant.     

Design, synthesis, and biological evaluation of glycine-based molecular tongs as inhibitors of Abeta1-40 aggregation in vitro

A series of N-terminus benzamides of glycine-based symmetric peptides, linked to m-xylylenediamine and 3,4′-oxydianiline spacers, were prepared and tested as inhibitors of β-amyloid peptide Aβ_1–40 aggregation in vitro. Compounds with good anti-aggregating activity were detected. Polyphenolic amides showed the highest anti-aggregating activity, with IC₅₀ values in the micromolar range. Structure–activity relationships suggested that π–π stacking and hydrogen-bonding interactions play a key role in the inhibition of Aβ_1–40 self-assembly leading to amyloid fibrils.     

New semicarbazones as gorge-spanning ligands of acetylcholinesterase and potential new drugs against Alzheimer’s disease: Synthesis,molecular modeling,NMR, and biological evaluation

Two new compounds (E)-2-(5,7-dibromo-3,3-dimethyl-3,4-dihydroacridin-1(2H)-ylidene)hydrazinecarbothiomide (3) and (E)-2-(5,7-dibromo-3,3-dimethyl-3,4-dhihydroacridin-1(2H)-ylidene)hydrazinecarboxamide (4) were synthesized and evaluated for their anticholinesterase activities. In vitro tests performed by NMR and Ellman’s tests, pointed to a mixed kinetic mechanism for the inhibition of acetylcholinesterase (AChE). This result was corroborated through further docking and molecular dynamics studies, suggesting that the new compounds can work as gorge-spanning ligands by interacting with two different binding sites inside AChE. Also, in silico toxicity evaluation suggested that these new compounds can be less toxic than tacrine.     

Design, synthesis and evaluation of isaindigotone derivatives as dual inhibitors for acetylcholinesterase and amyloid beta aggregation

A series of isaindigotone derivatives and analogues were designed, synthesized and evaluated as dual inhibitors of cholinesterases (ChEs) and self-induced β-amyloid (Aβ) aggregation. The synthetic compounds had IC(50) values at micro or nano molar range for cholinesterase inhibition, and some compounds exhibited strong inhibitory activity for AChE and high selectivity for AChE over BuChE, which were much better than the isaindigotone derivatives previously reported by our group. Most of these compounds showed higher self-induced Aβ aggregation inhibitory activity than a reference compound curcumin. The structure-activity relationship studies revealed that the derivatives with higher inhibition activity on AChE also showed higher selectivity for AChE over BuChE. Compound 6c exhibiting excellent inhibition for both AChE and self-induced Aβ aggregation was further studied using CD, EM, molecular docking and kinetics.     

Search for dual function inhibitors for Alzheimer's disease: synthesis and biological activity of acetylcholinesterase inhibitors of pyridinium-type and their Abeta fibril formation inhibition capacity

Alzheimer's disease (AD) represents the most common neurodegenerative disorder, which is expressed through decline of mental function. Current treatment approaches include acetylcholinesterase inhibitors and NMDA-receptor partial antagonists. The most explored recent approaches that are closely related to the pathogenesis of this disease based on formally articulated amyloid hypothesis are: Abeta fibril formation inhibitors, amyloid precursor protein, and secretase inhibitors. [Scarpini, E.; Scheltens, P.; Feldman, H. Lancet Neurol.2003, 2, 539] In view of the development of new AChE inhibitors as drugs capable of reducing the symptoms of AD, the capacity of newly synthesized AChE inhibitors of pyridinium-type to inhibit the AChE was examined and compared to those of other inhibitors of this type presented earlier. [Kapková, P.; Stiefl, N.; Sürig, U.; Engels, B.; Baumann, K.; Holzgrabe, U. Arch. Pharm. Pharm. Med. Chem.2003, 336, 523; Alptüzun, V.; Kapková, P.; Baumann, K.; Erciyas, E.; Holzgrabe, U. J. Pharm. Pharmacol.2003, 55, 1397] Furthermore, the anti-Abeta fibril formation property of AChE inhibitors of pyridinium- and bispyridinium-type was evaluated to expand their activity profile and to reveal potential additive pharmacological effects which may reinforce their therapeutic application besides their capacity of increasing acetylcholine levels. Abeta fibril formation studies were performed by means of thioflavin T fluorescence assay.     

Synthesis,molecular docking study and in vitro thymidine phosphorylase inhibitory potential of oxadiazole derivatives

We have synthesized oxadiazole derivatives (1–16), characterized by ¹H NMR, ¹³C NMR and HREI-MS and screened for thymidine phosphorylase inhibitory potential. All derivatives display varied degree of thymidine phosphorylase inhibition in the range of 1.10 ± 0.05 to 49.60 ± 1.30 μM when compared with the standard inhibitor 7-Deazaxanthine having an IC₅₀ value 38.68 ± 1.12 μM. Structure activity relationships (SAR) has been established for all compounds to explore the role of substitution and nature of functional group attached to the phenyl ring which applies imperious effect on thymidine phosphorylase activity. Molecular docking study was performed to understand the binding interaction of the most active derivatives with enzyme active site.     

Redox proteomics identification of oxidatively modified proteins in Alzheimer's disease brain and in vivo and in vitro models of AD centered around Abeta(1-42)

Alzheimer's disease is a progressive neurodegenerative disease associated with loss of memory and cognition. One hallmark of AD is the accumulation of amyloid beta-peptide (Abeta), which invokes a cascade of oxidative damage to neurons that can eventually result in neuronal death. Several markers of oxidative stress have been identified in AD brain, thus providing greater understanding into potential mechanisms involved in the disease pathogenesis and progression. In the present article, we review the application of redox proteomics to the identification of oxidized proteins in AD brain and also our recent findings on amyloid beta-peptide (Abeta)-associated in vivo and in vitro models of AD. Our redox proteomics approach has made possible the identification of specifically oxidized proteins in Alzheimer's disease (AD) brain, providing for the first time evidence on how oxidative stress plays a crucial role in AD-related neurodegeneration. The information obtained has great potential to aid in determining the molecular pathogenesis in and detecting disease markers of AD, as well as identifying potential targets for drug therapy in AD. Application of redox proteomics to study cellular events, especially related to disease dysfunction, may provide an efficient tool to understand the main mechanisms involved in the pathogenesis and progression of oxidative stress-related neurodegenerative disorders.     

Synthesis,in vitro urease inhibitory activity,and molecular docking studies of thiourea and urea derivatives

The current study deals with the synthesis of urea and thiourea derivatives 1–37 which were characterized by various spectroscopic techniques including FAB-MS, ¹H-, and ¹³C NMR. The synthetic compounds were subjected to urease inhibitory activity and compounds exhibited good to moderate urease inhibitory activity having IC₅₀ values in range of 10.11–69.80 µM. Compound 1 (IC₅₀ = 10.11 ± 0.11 µM) was found to be most active and even better as compared to the standard acetohydroxamic acid (IC₅₀ = 27.0 ± 0.5 µM). A limited structure–activity relationship (SAR) was established and the compounds were also subjected to docking studies to confirm the binding interactions of ligands (compounds) with the active site of enzyme.     

Synthesis,molecular docking analysis and carbonic anhydrase I-II inhibitory evaluation of new sulfonamide derivatives

New sulfonamide-hydrazone derivatives (3a-3n) were synthesized to evaluate their inhibitory effects on purified human carbonic anhydrase (hCA) I and II. The inhibition profiles of the synthesized compounds on hCA I-II isoenzyme were investigated by comparing their IC₅₀ and K_i values. Acetazolamide (5-acetamido-1,3,4-thiadiazole-2-sulfonamide, AZA) has also been used as a standard inhibitor. The compound 3e demonstrated the best hCA I inhibitory effect with a K_i value of 0.1676 ± 0.017 µM. Besides, the compound 3m showed the best hCA II inhibitory effect with a K_i value of 0.2880 ± 0.080 µM. Cytotoxicity of the compounds 3e and 3m toward NIH/3T3 mouse embryonic fibroblast cell line was observed and the compounds were found to be non-cytotoxic. Molecular docking studies were performed to investigate the interaction types between active compounds and hCA enzymes. Pharmacokinetic profiles of compounds were assessed by theoretical ADME predictions. As a result of this study a novel and potent class of CA inhibitors were identified with a good activity potential.