Synthesis,biological evaluation and docking studies of 2,3-dihydroquinazolin-4(1H)-one derivatives as inhibitors of cholinesterases

In search of potent inhibitors of cholinesterases, we have synthesized and evaluate a number of 2,3-dihydroquinazolin-4(1H)-one derivatives. The synthetic approach provided an efficient synthesis of the target molecules with excellent yield. All the tested compounds showed activity against both the enzymes in micromolar range. In many case, the inhibition of both enzymes are higher than or comparable to the standard drug galatamine. With the selectivity index of 2.3 for AChE, compound 5f can be considered as a potential lead compound with a feature of dual AChE/BChE inhibition with IC₅₀ = 1.6 ± 0.10 μM (AChE) and 3.7 ± 0.18 μM (BChE). Binding modes of the synthesized compounds were explored by using GOLD (Genetic Optimization for Ligand Docking) suit v5.4.1. The computed binding modes of these compounds in the active site of AChE and BChE provide an insight into the mechanism of inhibition of these two enzyme.     

Synthesis,crystal structure determination,biological screening and docking studies of N1-substituted derivatives of 2,3-dihydroquinazolin-4(1H)-one as inhibitors of cholinesterases

Pursuing the strategy of developing potent AChE inhibitors, we attempted to carry out the N¹-substitution of 2,3-dihydroquinazolin-4(1H)-one core. A set of 32 N-alkylated/benzylated quinazoline derivatives were synthesized, characterized and evaluated for their inhibition against cholinesterases. N-alkylation of the series of the compounds reported previously (N-unsubstituted) resulted in improved activity. All the compounds showed inhibition of both enzymes in the micromolar to submicromolar range. Structure activity relationship (SAR) of the 32 derivatives showed that N-benzylated compounds possess good activity than N-alkylated compounds. N-benzylated compounds 2ad and 2af were found very active with their IC₅₀ values toward AChE in submicromolar range (0.8 µM and 0.6 µM respectively). Binding modes of the synthesized compounds were explored by using GOLD (Genetic Optimization for Ligand Docking) suit v5.4.1. Computational predictions of ADMET studies reveal that all the compounds have good pharmacokinetic properties with no AMES toxicity and carcinogenicity. Moreover, all the compounds are predicted to be absorbed in human intestine and also have the ability to cross blood brain barrier. Overall, the synthesized compounds have established a structural foundation for the design of new inhibitors of cholinesterase.     

Design,synthesis and biological evaluation of benzofuran appended benzothiazepine derivatives as inhibitors of butyrylcholinesterase and antimicrobial agents

A series of bezofuran appended 1,5-benzothiazepine compounds 7a–v was designed, synthesized and evaluated as cholinesterase inhibitors. The biological assay experiments showed that most of the compounds displayed a clearly selective inhibition for butyrylcholinesterase (BChE), while a weak or no effect towards acetylcholinesterase (AChE) was detected. All analogs exhibited varied BChE inhibitory activity with IC₅₀ value ranging between 1.0?±?0.01 and 72?±?2.8?μM when compared with the standard donepezil (IC₅₀, 2.63?±?0.28?μM). Among the synthesized derivatives, compounds 7l, 7m and 7k exhibited the highest BChE inhibition with IC₅₀ values of 1.0, 1.0 and 1.8?μM, respectively. The results from a Lineweaver-Burk plot indicated a mixed-type inhibition for compound 7l with BChE. In addition, docking studies confirmed the results obtained through in vitro experiments and showed that most potent compounds bind to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of BChE active site. The synthesized compounds were also evaluated for their in vitro antibacterial and antifungal activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed high activity against both gram positive and gram negative bacteria and fungi.     

Synthesis and cholinesterase inhibition of cativic acid derivatives

Alzheimer’s disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. In a preliminary study, significant AChE inhibition was observed for the ethanolic extract of Grindelia ventanensis (IC₅₀ = 0.79 mg/mL). This result prompted us to isolate the active constituent, a normal labdane diterpenoid identified as 17-hydroxycativic acid (1), through a bioassay guided fractionation. Taking into account that 1 showed moderate inhibition of AChE (IC₅₀ = 21.1 μM), selectivity over butyrylcholinesterase (BChE) (IC₅₀ = 171.1 μM) and that it was easily obtained from the plant extract in a very good yield (0.15% w/w), we decided to prepare semisynthetic derivatives of this natural diterpenoid through simple structural modifications. A set of twenty new cativic acid derivatives (3–6) was prepared from 1 through transformations on the carboxylic group at C-15, introducing a C2–C6 linker and a tertiary amine group. They were tested for their inhibitory activity against AChE and BChE and some structure–activity relationships were outlined. The most active derivative was compound 3c, with an IC₅₀ value of 3.2 μM for AChE. Enzyme kinetic studies and docking modeling revealed that this inhibitor targeted both the catalytic active site and the peripheral anionic site of this enzyme. Furthermore, 3c showed significant inhibition of AChE activity in SH-SY5Y human neuroblastoma cells, and was non-cytotoxic.     

Discovery,molecular dynamic simulation and biological evaluation of structurally diverse cholinesterase inhibitors with new scaffold through shape-based pharmacophore virtual screening

Designing small molecule inhibitors targeting cholinesterases (ChEs) is considered as an efficient strategy for the treatment of Alzheimer′s disease (AD). In the present study, based on a shaped-based pharmacophore (SBP) model that we reported previously, virtual screening was performed on four commercial compound databases, from which eight small molecules containing new structurally scaffolds were retained and evaluated. In general, six of these potential hits were identified to be selective ChEs inhibitors. Three compounds exhibited IC₅₀ values and K_i values in micromolar range on acetylcholinesterase (AChE), the most active compound 4 showed IC₅₀ value of 6.31 ± 2.68 μM and K_i value of 4.76 μM. Other three compounds displayed IC₅₀ values and K_i values in micromolar range on butyrylcholinesterase (BChE) with high target selectivity, the most active compound 1 showed IC₅₀ value of 3.87 ± 2.48 μM and K_i value of 1.52 μM. Multiple biological evaluations were performed to determine their cytotoxicity, cyto-protective effects, antioxidant effect as well as druglike properties. These compounds provide new cores for the further design and optimization, with the aim to discover new ChEs inhibitors for the treatment of AD.     

Amyloid peptide Abeta(1-42) binds selectively and with picomolar affinity to alpha7 nicotinic acetylcholine receptors

We have recently reported evidence that a very high affinity interaction between the beta-amyloid peptide Abeta(1-42) and the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) may be a precipitating event in the formation of amyloid plaques in Alzheimer's disease. In the present study, the kinetics for the binding of Abeta(1-42) to alpha7nAChR and alpha4beta2nAChR were determined using the subtype-selective nicotinic receptor ligands [(3)H]methyllycaconitine and [(3)H]cytisine. Synaptic membranes prepared from rat and guinea pig cerebral cortex and hippocampus were used as the source of receptors. Abeta(1-42) bound to the alpha7nAChR with exceptionally high affinity, as indicated by K(i) values of 4.1 and 5.0 pM for rat and guinea pig receptors, respectively. When compared with the alpha7nAChR, the affinity of Abeta(1-42) for the alpha4beta2nAChR was approximately 5,000-fold lower, as indicated by corresponding K(i) values of 30 and 23nM. The results of this study support the concept that an exceptionally high affinity interaction between Abeta(1-42) and alpha7nAChR could serve as a precipitating factor in the formation of amyloid plaques and thereby contribute to the selective degeneration of cholinergic neurons that originate in the basal forebrain and project to the cortex and hippocampus.     

Design,synthesis and biological evaluation of selected 3-[3-(amino) propoxy] benzenamines as acetylcholinesterase inhibitors

The present paper describes design, synthesis, and biological evaluation of a series of some 3-[3-(amino)propoxy]benzenamines as acetylcholinesterase inhibitors using mice as a model and piracetam as a reference drug. The structures of these compounds were confirmed by spectral analysis and compounds were tested for memory enhancing activity using elevated plus maze test and acetylcholinesterase inhibitory assay. The inhibitory range of synthesized compounds was from 8.99 to 28.31 μM. The synthesized compounds possessed higher or equivalent percent retention as compared to piracetam at 1 mg/kg with no other CNS-related activities (locomotor and muscle relaxant, analgesic and anticonvulsant activities). Compound 3-[3-(imidazolo)propoxy]benzenamine has shown significant dose-dependent (1 and 3 mg/kg) memory enhancing activity, while 3-[3-(pyrrolidino)propoxy]benzenamine also showed activity equivalent to reference drug piracetam at 1 mg/kg. Both compounds 3-[3-(pyrrolidino)propoxy]benzenamine and 3-[3-(imidazolo)propoxy]benzenamine were also found to show AChE inhibition with IC₅₀ value of 8.99 and 17.87 μM. The molecular docking, MM-GBSA and molecular dynamics simulation studies were performed in order to establish a relationship between the biological results. RMSD, root-mean-square fluctuations, and interaction patterns of 10a–AChE and Sck–AChE complexes proved that the binding affinity of 10a toward AChE was highly stable with the proposed binding orientations.     

Design,synthesis and biological evaluation of imidazo[1,5-a]pyrazin-8(7H)-one derivatives as BRD9 inhibitors

BRD9 is the subunit of mammalian SWI/SNF chromatin remodeling complex (BAF). SWI/SNF complex mutations were found in nearly 20% of human cancers. The biological role played by BRD9 bromodomain remains poorly understood, and it is therefore imperative to identify potent and highly selective inhibitors to effectively explore the biology of individual bromodomain proteins. In this paper, we synthesized a series of imidazo[1,5-a]pyrazin-8(7H)-one derivatives as potent BRD9 inhibitors and evaluated their BRD9 inhibitory activity in vitro and anti-proliferation effects against tumor cells. Gratifyingly, compound 27 and 29 exhibited robust potency of BRD9 inhibition with IC₅₀ values of 35 and 103?nM respectively. Docking studies were performed to explain the structure-activity relationship. Furthermore, compound 27 potently inhibited cell proliferation in cell lines A549 and EOL-1 with an IC₅₀ value of 6.12?μM and 1.76?μM respectively. The chemical probe, compound 27, was identified that should prove to be useful in further exploring BRD9 bromodomain biology in both in vitro and in vivo settings.     

Synthesis and in vitro anticancer evaluation of some fused indazoles,quinazolines and quinolines as potential EGFR inhibitors

derivatives of benzo[g]indazole 5a, b, benzo[h]quinazoline 7, 12a-c, 13a-c and 15a-c and benzo[h]quinoline 17a-c and 19a-c were synthesized from 6-methoxy-3,4-dihydronaphthalen-1(2H)-one (1). Anticancer activity of all the synthesized compounds was evaluated against four cancerous cell lines; HepG2, MCF-7, HCT116 and Caco-2. MCF-7 cells emerged as the most sensitive cell line against the target compounds. All the examined compounds, except 5a and 5b, displayed potent to moderate anticancer activity against MCF-7 cells with an IC₅₀ values ranging from 7.21 to 21.55 µM. In particular, compounds 15c and 19b emerged as the most potent derivatives against EGFR-expressing MCF-7 cells with IC₅₀ values = 7.70 ± 0.39 and 7.21 ± 0.43 μM, respectively. Additionally, both compounds did not display any significant cytotoxicity towards normal BHK-21 fibroblast cells (IC₅₀ value > 200 µM), thereby providing a good safety profile as anticancer agents. Furthermore, compounds 15c and 19b displayed potent inhibitory activity towards EGFR in the sub-micromolar range (IC₅₀ = 0.13 ± 0.01 and 0.14 ± 0.01 μM, respectively), compared to that of Erlotinib (IC₅₀ = 0.11 ± 0.01 μM). Docking studies for 15c and 19b into EGFR active site was carried out to explore their potential binding modes. Therefore, compounds 15c and 19b can be considered as interesting candidates for further development of more potent anticancer agents.     

A Facile Synthesis of cis-9-[4-(1,2-Dihydroxyethyl)-cyclopent-2-enyl]guanine and Its Derivative

Abstract

The synthesis of carbocyclic nucleosides, cis-9-[4-(1,2-dihydroxyethyl)-cyclopent-2-enyl]guanine (3) and cis-2-amino-6-cyclopropylamino-9-[4-(1,2-dihydroxyethyl)-cyclopent-2-enyl]guanine (4), was achieved from cyclopentadiene (5) in five and six steps, respectively. This route involves a hetero Diels-Alder reaction and a Pd(0)-catalyzed coupling reaction.     

N-(4-Hydroxyphenyl)-3,4,5-trimethoxybenzamide derivatives as potential memory enhancers: synthesis,biological evaluation and molecular simulation studies

The present paper describes the synthesis, biological evaluation and molecular simulation studies of a series of N-(4-hydroxyphenyl)-3,4,5-trimethoxybenzamide derivatives with N,N-dialkylaminoethoxy/propoxy moiety as potential memory enhancers with acetylcholinesterase-inhibiting activity having IC₅₀ in low micromolar range (4.0–16.5 μM). All the compounds showed a good degree of agreement between in vivo and in vitro results as most of these derivatives showed dose-dependent increase in percent retention. Compound 10a showed significant % retention of 84.73 ± 4.51 as compared to piracetam (46.88 ± 5.42) at 3 mg kg^?1 and also exhibited a maximal percent inhibition of 97% at 50 μM. Molecular docking, MM-GBSA and molecular simulation studies were performed establishing a correlation between the experimental biology and in silico results. In silico results indicate that all the compounds have better docking scores and predicted binding free energies as compared to cocrystallized ligand with the best potent ligand retaining conserved hydrophobic interactions with residues of catalytic triad (HIS447), catalytic anionic site (CAS) (TRP86, TYR337, PHE338) and peripheral anionic site (PAS) (TYR72, TYR124, TRP286 and TYR341). Root mean square deviation (RMSD = 2.4 Å) and root mean square fluctuations of 10a–AChE complex during simulation proved its stable nature in binding toward acetylcholinesterase. The docked conformation of 10a and other analogs at the binding site have also been simulated with polar and nonpolar interactions interlining the gorge residues from PAS to catalytic triad.     

In vitro and in silico evaluation of fucosterol from Sargassum horridum as potential human acetylcholinesterase inhibitor

The fucosterol has been reported numerous biological activities. In this study, the activity in vitro of the fucosterol from Sargassum horridum as potential human acetylcholinesterase inhibitor was evaluated. The structural identification was obtained by nuclear magnetic resonance (NMR) spectroscopy and based on experimental data, we combined docking and molecular dynamics simulations coupled to the molecular-mechanics-generalized-born-surface-area approach to evaluating the structural and energetic basis for the molecular recognition of fucosterol and neostigmine at the binding site of acetylcholinesterase (AChE). In addition, the Lineweaver–Burk plot showed the nature of a non-competitive inhibition. The maximum velocity (V_max) and the constant of Michaelis–Menten (K_m) estimated for fucosterol (0.006 µM) were 0.015 1/V_o (ΔA/h and 6.399 1/[ACh] mM^?1, respectively. While, for neostigmine (0.14 µM), the V_max was 0.022 1/V_o (ΔA/h) and K_m of 6.726 1/[ACh] mM^?1, these results showed a more effective inhibition by fucosterol respect to neostigmine. Structural analysis revealed that neostigmine reaches the AChE binding site reported elsewhere, whereas fucosterol can act as a no-competitive and competitive acetylcholinesterase inhibitor, in agree with kinetic enzymatic experiments. Binding free energy calculations revealed that fucosterol reaches the acetylcholinesterase binding site with higher affinity than neostigmine, which is according to experimental results. Whereas the per-residue decomposition free energy analysis let us identify crucial residues involved in the molecular recognition of ligands by AChE. Results corroborate the ability of theoretical methods to provide crucial information at the atomic level about energetic and structural differences in the binding interaction and affinity from fucosterol with AChE.

Communicated by Ramaswamy H. Sarma     

Synthesis,biological evaluation and in silico studies with 4-benzylidene-2-phenyl-5(4H)-imidazolone-based benzenesulfonamides as novel selective carbonic anhydrase IX inhibitors endowed with anticancer activity

In the presented work, we report the synthesis of a series of 4-benzylidene-2-phenyl-5(4H)-imidazolone-based benzenesulfonamides 7a-f via the Erlenmeyer–Plöchl reaction. All the prepared imidazolones 7a-f were evaluated as inhibitors of human (h) carbonic anhydrases (CA, EC 4.2.1.1) cytosolic isoforms hCA I and II, as well as transmembrane tumor-associated isoforms hCA IX and XII. All the tested hCA isoforms were inhibited by the prepared imidazolones 7a-f in variable degrees with the following K_Is ranges: 673.2–8169 nM for hCA I, 61.2–592.1 nM for hCA II, 23–155.4 nM for hCA XI, and 21.8–179.6 nM for hCA XII. In particular, imidazolones 7a, 7e, and 7f exhibited good selectivity towards the tumor-associated isoforms (CAs IX and XII) over the off-target cytosolic (CAs I and II) with selectivity index (SI) in the range of 6.2–19.4 and 3.3–8, respectively. Moreover, imidazolones 7a-f were screened for their anticancer activity in one dose (10⁻⁵ M) assay against a panel of 60 cancer cell lines according to US-NCI protocol. Furthermore, 7a, 7e and 7f were evaluated for their anti-proliferative activity against colorectal cancer HCT-116 and breast cancer MCF-7 cell lines. Furthermore, 7e and 7f were screened for cell cycle disturbance and apoptosis induction in HCT-116 cells. Finally, a molecular docking study was carried out to rationalize the obtained results.     

1-Aryl-3-(4-methoxybenzyl)ureas as potentially irreversible glycogen synthase kinase 3 inhibitors: Synthesis and biological evaluation

Glycogen synthase kinase 3 (GSK-3) has become known for its multifactorial involvement in the pathogenesis of Alzheimer’s disease. In this study, a benzothiazole- and benzimidazole set of 1-aryl-3-(4-methoxybenzyl)ureas were synthesised as proposed Cys199-targeted covalent inhibitors of GSK-3β, through the incorporation of an electrophilic warhead onto their ring scaffolds. The nitrile-substituted benzimidazolylurea 2b (IC₅₀ = 0.086 ± 0.023 µM) and halomethylketone-substituted benzimidazolylurea 9b (IC₅₀ = 0.13 ± 0.060 µM) displayed high GSK-3β inhibitory activity, in comparison to reference inhibitor AR-A014418 (1, IC₅₀ = 0.072 ± 0.043) in our assay. The results suggest further investigation of 2b and 9b as potential covalent inhibitors of GSK-3β, since a targeted interaction might provide improved kinase-selectivity.     

Synthesis and pharmacological evaluation of 4-(3,4-dichlorophenyl)-N-methyl-1,2,3,4-tetrahydronaphthalenyl amines as triple reuptake inhibitors

The present work describes a series of novel chiral amines that potently inhibit the in vitro reuptake of serotonin, norepinephrine and dopamine (triple reuptake inhibitors) and were active in vivo in a mouse model predictive of antidepressant like activity. The detailed synthesis and in vitro activity and ADME profile of compounds is described, which represent a previously undisclosed triple reuptake inhibitor chemotype.     

Synthesis and evaluation of 4-(2-hydroxypropyl)piperazin-1-yl) derivatives as Hsp90 inhibitors

We previously reported 4-(3-((6-bromonaphthalen-2-yl)oxy)-2-hydroxypropyl)-N,N-dimethylpiperazine-1-sulfonamide (1) as a novel heat shock protein 90 inhibitor with moderate activity. In our ongoing efforts for the discovery of Hsp90 modulators we undertake structural investigations on 1. Series of the titled compound were designed, synthesized and evaluated. We have found that compounds with a hydroxyl group at C-4 of the aryl ring on the piperazine moiety possess Hsp90 inhibition properties. Compound 6f with improved activity could be further developed and optimized as Hsp90 inhibitor.     

Synthesis and in vitro activity of N-benzyl-1-(2,3-dichlorophenyl)-1H-tetrazol-5-amine P2X(7) antagonists

Synthesis and biological evaluation of a novel class of substituted N-benzyl-1-(2,3-dichlorophenyl)-1H-tetrazol-5-amine derivatives resulted in the identification of potent P2X₇ antagonists. These compounds were assayed for activity at both the human and rat P2X₇ receptors. On the benzyl moiety, a variety of functional groups were tolerated, including both electron-withdrawing and electron-donating substituents. Ortho-substitution on the benzyl group provided the greatest potency. The ortho-substituted analogs showed approximately 2.5-fold greater potency at human compared to rat P2X₇ receptors. Compounds 12 and 38 displayed hP2X₇pIC₅₀s >7.8 with less than 2-fold difference in potency at the rP2X₇.     

Design,synthesis, and biological evaluation of 2-amino-N-(2-methoxyphenyl)-6-((4-nitrophenyl)sulfonyl)benzamide derivatives as potent HIV-1 Vif inhibitors

Viral infectivity factor (Vif) is one of the accessory protein of human immunodeficiency virus type I (HIV-1) that inhibits host defense factor, APOBEC3G (A3G), mediated viral cDNA hypermutations. Previous work developed a novel Vif inhibitor 2-amino-N-(2-methoxyphenyl)-6-((4-nitrophenyl)thio)benzamide (1) with strong antiviral activity. Through optimizations on the two side branches, a series of compound 1 derivatives (2–18) were designed, synthesized and tested in vitro for their antiviral activities. The biological results showed that compound 5 and 16 inhibited the virus replication efficiently with EC₅₀ values of 9.81 and 4.62 μM. Meanwhile, low cytotoxicities on H9 cells were observed for the generated compounds by the MTT assay. The structure–activity relationship of compound 1 was preliminarily clarified, which gave rise to the development of more potent Vif inhibitors.     

Synthesis and evaluation of 2-amino-6-fluoro-9-(2-hydroxyethoxymethyl)purine esters as potential prodrugs of acyclovir

2-Amino-6-fluoro-9-(2-hydroxyethoxymethyl)purine (2) and its ester derivatives 4a–d were synthesized as potential prodrugs of acyclovir, and were evaluated for their oral acyclovir bioavailability in rats and in vivo antiviral efficacy in HSV-1-infected mice. Treatment of 2-amino-6-chloro-9-(2-hydroxyethoxymethyl)purine (3) with trimethylamine in THF/DMF (4:1) followed by a reaction of the resulting trimethylammonium chloride salt 5 with KF in DMF gave 2 in 78% yield. Esterification of 2 with an appropriate acid anhydride (Ac₂O, (EtCO)₂O, (n-PrCO)₂O, or (i-PrCO)₂O) in DMF in the presence of a catalytic amount of DMAP at room temperature produced the esters 4a–d in 90–98% yields. Of the prodrugs tested in rats, the isobutyrate 4d achieved the highest mean urinary recovery of acyclovir (51%) that is 5.7-fold higher than that of acyclovir (9%) and comparable to that of valacyclovir (50%). The prodrug 4d protected dose-dependently the mortality of HSV-1-infected mice, and the group treated with 4d at a dose of 400 mg/kg showed the longest mean survival day (14.6 ± 3.1 days) (mean ± S.D.).     

Synthesis and evaluation of 4-(1,3,4-oxadiazol-2-yl)-benzenesulfonamides as potent carbonic anhydrase inhibitors

Human Carbonic anhydrase (hCA) I and II are crucial targets for anti-acute mountain sickness. Twenty-one 4-(1,3,4-oxadiazol-2-yl) benzenesulfonamides were synthesized and screened against these two isoforms. The results illustrated that 5c, 5g, 5h, 5k were more potent against both hCA I and II than clinical drug AAZ. In particular, the value of compound 5c with hCA I (18.08 nM) was over 84-fold more than of AAZ with hCA I. The data of docking simulations were also in accord with the tendency of inhibitive activities. Furthermore, compound 6h, the methanesulfonate of 5h, showed better anti-hypoxia activity than AAZ in vivo, making it interesting lead compound.