Synthesis of 4-thiazolidinone analogs as potent in vitro anti-urease agents

4-Thiazolidinone analogs 1–20 were synthesized, characterized by ¹H NMR and EI–MS and investigated for urease inhibitory activity. All twenty (20) analogs exhibited varied degree of urease inhibitory potential with IC₅₀ values 1.73–69.65 μM, if compared with standard thiourea having IC₅₀ value of 21.25 ± 0.15 μM. Among the series, eight derivatives 3, 6, 8, 10, 15, 17, 19, and 20 showed outstanding urease inhibitory potential with IC₅₀ values of 9.34 ± 0.02, 14.62 ± 0.03, 8.43 ± 0.01, 7.3 ± 0.04, 2.31 ± 0.002, 5.75 ± 0.003, 8.81 ± 0.005, and 1.73 ± 0.001 μM, respectively, which is better than the standard thiourea. The remaining analogs showed good to excellent urease inhibition. The binding interactions of these compounds were confirmed through molecular docking studies.     

Design and synthesis of biphenyl derivatives as mushroom tyrosinase inhibitors

Two new series of biphenyls, analogs of aglycone of natural product fortuneanoside E, were prepared using Suzuki–Miyaura cross-coupling and selective magnesium iodide demethylation/debenzylation, and their mushroom tyrosinase inhibitory activity was evaluated. Most of the 4-hydroxy-3,5-dimethoxyphenyl biphenyl compounds (series II, 20–36) were in general more active than 3,4,5-trimethoxyphenyl biphenyl compounds (series I, 1–19). Structure–activity relationships study showed that monosaccharide substituents, such as glucose, were not necessary and the presence of 4-hydroxy-3,5-dimethoxyphenyl moiety was crucial for inhibitory activity. Among the compounds synthesised, compound 21 (IC₅₀ = 0.02 mM) was found to be the most active one, which exhibited an activity that was 7 times higher than that of fortuneanoside E (IC₅₀ = 0.14 mM) and 10 times higher than that of arbutin (IC₅₀ = 0.21 mM), known as potent tyrosinase inhibitors. The inhibition kinetics analyzed by Lineweaver–Burk plots revealed that compound 21 was a competitive inhibitor (K_i = 0.015 mM).     

Inhibition of CTP synthase from Escherichia coli by xanthines and uric acids

CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a recognized target for the development of anticancer, antiviral, and antiprotozoal agents. Xanthine and related compounds inhibit CTPS activity (IC₅₀ = 0.16–0.58 mM). The presence of an 8-oxo function (i.e., uric acids) enhances inhibition (IC₅₀ = 0.060–0.121 mM). An intact purine ring with anionic character favors inhibition. In general, methylation of the purine does not significantly affect inhibition.     

Synthesis,biological evaluation and molecular docking of N-phenyl thiosemicarbazones as urease inhibitors

Urease is an important enzyme which breaks urea into ammonia and carbon dioxide during metabolic processes. However, an elevated activity of urease causes various complications of clinical importance. The inhibition of urease activity with small molecules as inhibitors is an effective strategy for therapeutic intervention. Herein, we have synthesized a series of 19 benzofurane linked N-phenyl semithiocarbazones (3a–3s). All the compounds were screened for enzyme inhibitor activity against Jack bean urease. The synthesized N-phenyl thiosemicarbazones had varying activity levels with IC₅₀ values between 0.077 ± 0.001 and 24.04 ± 0.14 μM compared to standard inhibitor, thiourea (IC₅₀ = 21 ± 0.11 μM). The activities of these compounds may be due to their close resemblance of thiourea. A docking study with Jack bean urease (PDB ID: 4H9M) revealed possible binding modes of N-phenyl thiosemicarbazones.     

1,1-Difluoroethyl-substituted triazolothienopyrimidines as inhibitors of a human urea transport protein (UT-B): New analogs and binding model

The kidney urea transport protein UT-B is an attractive target for the development of small-molecule inhibitors with a novel diuretic (‘urearetic’) action. Previously, two compounds in the triazolothienopyrimidine scaffold (1a and 1c) were reported as UT-B inhibitors. Compound 1c incorporates a 1,1-difluoroethyl group, which affords improved microsomal stability when compared to the corresponding ethyl-substituted compound 1a. Here, a small focused library (4a–4f) was developed around lead inhibitor 1c to investigate the requirement of an amidine-linked thiophene in the inhibitor scaffold. Two compounds (4a and 4b) with nanomolar inhibitory potency (IC₅₀ ≈ 40 nM) were synthesized. Computational docking of lead structure 1c and 4a–4f into a homology model of the UT-B cytoplasmic surface suggested binding with the core heterocycle buried deep into the hydrophobic pore region of the protein.     

Synthesis,antileishmanial and antitrypanosomal activities of N-substituted tetrahydro-β-carbolines

A series of N-substituted tetrahydro-β-carbolines were synthesized and screened for antileishmanial activity through an in vitro assay that involves promastigotes and axenic amastigotes of Leishmania donovani, the causative agent for visceral leishmaniasis. The thiophen-2-yl analogs 9b and 11f and naphthyl analog 11h were found to show significant activity against promastigotes with IC₅₀ values of 12.7, 9.1 and 22.1 μM, respectively. Analogs 9b and 11h were also effective against axenic amastigotes with IC₅₀ values of 62.8 and 87.6 μM, respectively. The antileishmanial activity of analogs was then tested in human macrophage cell line infected with L. donovani amastigotes and 2-naphthyl linked analog 11h was found to be effective with IC₅₀ value of 28.3 μM. Several analogs also displayed antitrypanosomal activity against Trypanosoma brucei, the causative agent for human African trypanosomiasis. Compounds 11e, 11f and 11h were more effective than others with IC₅₀ values of 1.0, 8.9 and 10.2 μM, respectively. All synthesized analogs were not cytotoxic towards mammalian cell lines including Vero (monkey kidney fibroblasts), HEPG2 (human hepatoma cells), LLC-PK₁ (pig kidney epithelial cells) and THP-1 (human macrophages).     

γ-Lactams as glycinamide replacements in cyclohexane-based CC chemokine receptor 2 (CCR2) antagonists

We describe the design, synthesis, and evaluation, of γ-lactams as glycinamide replacements within a series of di- and trisubstituted cyclohexane CCR2 antagonists. The lactam-containing trisubstituted cyclohexanes proved to be more potent than the disubstituted analogs, as trisubstituted analog, lactam 13, displayed excellent activity (CCR2 binding IC₅₀ = 1.0 nM and chemotaxis IC₅₀ = 0.5 nM) and improved metabolic stability over its parent glycinamide.     

Design,synthesis and pharmacological characterization of coumarin-based fluorescent analogs of excitatory amino acid transporter subtype 1 selective inhibitors,UCPH-101 and UCPH-102

The excitatory amino acid transporters (EAATs) play a pivotal role in regulating the synaptic concentration of glutamate in the mammalian central nervous system. To date, five different subtypes have been identified, named EAAT15 in humans (and GLAST, GLT-1, EAAC1, EAAT4, and EAAT5, respectively, in rodents). Recently, we have published and presented a structure–activity relationship (SAR) study of a novel class of selective inhibitors of EAAT1 (and GLAST), with the analogs UCPH-101 (IC₅₀ = 0.66 μM) and UCPH-102 (IC₅₀ = 0.43 μM) being the most potent inhibitors in the series. In this paper, we present the design, synthesis and pharmacological evaluation of six coumarin-based fluorescent analogs of UCPH-101/102 as subtype-selective inhibitors at EAAT1. Analogs 1114 failed to inhibit EAAT1 function (IC₅₀ values >300 μM), whereas analogs 15 and UCPH-102F inhibited EAAT1 with IC₅₀ values in the medium micromolar range (17 μM and 14 μM, respectively). Under physiological pH no fluorescence was observed for analog 15, while a bright blue fluorescence emission was observed for analog UCPH-102F. Regrettably, under confocal laser scanning microscopy selective visualization of expression of EAAT1 over EAAT3 was not possible due to nonspecific binding of UCPH-102F.     

Synthesis,in vitro evaluation and molecular docking studies of thiazole derivatives as new inhibitors of α-glucosidase

A series of thiazole derivatives 1–21 were prepared, characterized by EI-MS and ¹H NMR and evaluated for α-glucosidase inhibitory potential. All twenty one derivatives showed good α-glucosidase inhibitory activity with IC₅₀ value ranging between 18.23 ± 0.03 and 424.41 ± 0.94 μM when compared with the standard acarbose (IC₅₀, 38.25 ± 0.12 μM). Compound (8) (IC₅₀, 18.23 ± 0.03 μM) and compound (7) (IC₅₀ = 36.75 ± 0.05 μM) exhibited outstanding inhibitory potential much better than the standard acarbose (IC₅₀, 38.25 ± 0.12 μM). All other analogs also showed good to moderate enzyme inhibition. Molecular docking studies were carried out in order to find the binding affinity of thiazole derivatives with enzyme. Studies showed these thiazole analogs as a new class of α-glucosidase inhibitors.     

Design,synthesis and biological evaluation of di-substituted cinnamic hydroxamic acids bearing urea/thiourea unit as potent histone deacetylase inhibitors

A novel class of di-substituted cinnamic hydroxamic acid derivatives containing urea or thiourea unit was designed, synthesized and evaluated as HDAC inhibitors. All tested compounds demonstrated significant HDAC inhibitory activities and anti-proliferative effects against diverse human tumor cell lines. Among them, 7l exhibited most potent pan-HDAC inhibitory activity, with an IC₅₀ value of 130 nM. It also showed strong cellular inhibition against diverse cell lines including HCT-116, MCF-7, MDB-MB-435 and NCI-460, with GI₅₀ values of 0.35, 0.22, 0.51 and 0.48 μM, respectively.     

Synthesis of 2-acylated and sulfonated 4-hydroxycoumarins: In vitro urease inhibition and molecular docking studies

Sixteen 4-hydroxycoumarin derivatives were synthesized, characterized through EI-MS and ¹H NMR and screened for urease inhibitory potential. Three compounds exhibited better urease inhibition than the standard inhibitor thiourea (IC₅₀ = 21 ± 0.11 μM) while other four compounds exhibited good to moderate inhibition with IC₅₀ values between 29.45 ± 1.1 μM and 69.53 ± 0.9 μM. Structure activity relationship was established on the basis of molecular docking studies, which helped to predict the binding interactions of the most active compounds.     

Synthesis of alpha amylase inhibitors based on privileged indole scaffold

Twenty five derivatives of indole carbohydrazide (1–25) had been synthesized. These compounds were characterized using ¹H NMR and EI-MS, and further evaluated for their α-amylase inhibitory potential. The analogs (1–25) showed varying degree of α-amylase inhibitory potential.ranging between 9.28 and 599.0 µM when compared with standard acarbose having IC₅₀ value 8.78 ± 0.16 µM. Six analogs, 25 (IC₅₀ = 9.28 ± 0.153 µM), 22 (IC₅₀ = 9.79 ± 0.43 µM), 4 (IC₅₀ = 11.08 ± 0.357 µM), 1 (IC₅₀ = 12.65 ± 0.169 µM), 8 (IC₅₀ = 21.37 ± 0.07 µM) and 14 (IC₅₀ = 43.21 ± 0.14 µM) showed potent α-amylase inhibition as compared to the standard acarbose (IC₅₀ = 8.78 ± 0.16 µM). All other analogs displayed good to moderate inhibitory potential. Structure-activity relationship was established through the interaction of the active compounds with enzyme active site with the help of docking studies.     

Structural requirement(s) of N-phenylthioureas and benzaldehyde thiosemicarbazones as inhibitors of melanogenesis in melanoma B 16 cells

In order to define the structural requirements of phenylthiourea (PTU), a series of thiourea and thiosemicarbazone analogs were prepared and evaluated as inhibitors of melanogenesis in melanoma B16 cells. The most potent analog was 2-(4-tert-butylbenzylidene)hydrazinecarbothioamide (1u) with an IC₅₀ value of 2.7 μM in inhibition of melanogenesis. The structure for potent inhibitory activity of these derivatives are required with the direct connection of π-planar structure to thiourea without steric hinderance in PTU derivatives and the hydrophobic substituent at para position in case of semicarbazones.     

Cassava (Manihot esculenta Crantz of cv. KU50) peroxidase and its potential for the detection of some thiol compounds based on the inhibitory effect of 3,3′,5,5′-tetramethylbenzidine oxidation

Cassava peroxidase (CSP) isolated from cassava leaves (Manihot esculenta Crantz of cv. KU50) was purified by DEAE and concanavalin-A column chromatography. CSP was a haem-containing cationic glycoprotein with the molecular weight of 38 and 44 kDa determined by MALDI-TOF-MS. Its kinetic catalysis in the presence and absence of some thiols were investigated and compared to those of horseradish and soybean peroxidases by using urea hydrogen peroxide (UHP) and 3,3′,5,5′-tetramethylbenzidine (TMB) as substrates. Inhibitory effects of some pesticides containing thiol groups such as thiosemicabazide, thiourea and thiophanate-methyl on TMB oxidation were graphically demonstrated their ability to be either competitive or noncompetitive inhibitors, depending on their properties. The degrees of inhibition were expressed as K_i and IC₅₀ values. The applicable range for the detection of thiosemicabazide in solution was found to be in the range of 10–100 μM, whereas those of thiourea and thiophanate-methyl were 40–400 μM and 10–460 μM, respectively. On the contrary, the inhibitory effects of some phenolic pollutants; 4-nitrophenol, 4-phenylphenol and pentachlorophenol on TMB oxidation were not significantly observed and the phenomenon was discussed.     

Synthesis,cholinesterase inhibition and molecular modelling studies of coumarin linked thiourea derivatives

Alzheimer’s disease is among the most widespread neurodegenerative disorder. Cholinesterases (ChEs) play an indispensable role in the control of cholinergic transmission and thus the acetylcholine level in the brain is enhanced by inhibition of ChEs. Coumarin linked thiourea derivatives were designed, synthesized and evaluated biologically in order to determine their inhibitory activity against acetylcholinesterases (AChE) and butyrylcholinesterases (BChE). The synthesized derivatives of coumarin linked thiourea compounds showed potential inhibitory activity against AChE and BChE. Among all the synthesized compounds, 1-(2-Oxo-2H-chromene-3-carbonyl)-3-(3-chlorophenyl)thiourea (2e) was the most potent inhibitor against AChE with an IC₅₀ value of 0.04 ± 0.01 μM, while 1-(2-Oxo-2H-chromene-3-carbonyl)-3-(2-methoxyphenyl)thiourea (2b) showed the most potent inhibitory activity with an IC₅₀ value of 0.06 ± 0.02 μM against BChE. Molecular docking simulations were performed using the homology models of both cholinesterases in order to explore the probable binding modes of inhibitors. Results showed that the novel synthesized coumarin linked thiourea derivatives are potential candidates to develop for potent and efficacious acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors.     

Structure–activity relationship study of 4-(thiazol-5-yl)benzoic acid derivatives as potent protein kinase CK2 inhibitors

Two classes of modified analogs of 4-(thiazol-5-yl)benzoic acid-type CK2 inhibitors were designed. The azabenzene analogs, pyridine- and pyridazine-carboxylic acid derivatives, showed potent protein kinase CK2 inhibitory activities [IC₅₀ (CK2α) = 0.014–0.017 μM; IC₅₀ (CK2α′) = 0.0046–0.010 μM]. Introduction of a 2-halo- or 2-methoxy-benzyloxy group at the 3-position of the benzoic acid moiety maintained the potent CK2 inhibitory activities [IC₅₀ (CK2α) = 0.014–0.016 μM; IC₅₀ (CK2α′) = 0.0088–0.014 μM] and led to antiproliferative activities [CC₅₀ (A549) = 1.5–3.3 μM] three to six times higher than those of the parent compound.     

Design,synthesis, and biological evaluation of potent thiosemicarbazone based cathepsin L inhibitors

A small library of 36 functionalized benzophenone thiosemicarbazone analogs has been prepared by chemical synthesis and evaluated for their ability to inhibit the cysteine proteases cathepsin L and cathepsin B. Inhibitors of cathepsins L and B have the potential to limit or arrest cancer metastasis. The six most active inhibitors of cathepsin L (IC₅₀ < 85 nM) in this series incorporate a meta-bromo substituent in one aryl ring along with a variety of functional groups in the second aryl ring. These six analogs are selective for their inhibition of cathepsin L versus cathepsin B (IC₅₀ > 10,000 nM). The most active analog in the series, 3-bromophenyl-2′-fluorophenyl thiosemicarbazone 1, also efficiently inhibits cell invasion of the DU-145 human prostate cancer cell line.     

Synthesis and α-glucosidase inhibitory activity evaluation of N-substituted aminomethyl-β-d-glucopyranosides

A series of N-substituted 1-aminomethyl-β-d-glucopyranoside derivatives was prepared. These novel synthetic compounds were assessed in vitro for inhibitory activity against yeast α-glucosidase and both rat intestinal α-glucosidases maltase and sucrase. Most of the compounds displayed α-glucosidase inhibitory activity, with IC₅₀ values covering the wide range from 2.3 μM to 2.0 mM. Compounds 19a (IC₅₀ = 2.3 μM) and 19b (IC₅₀ = 5.6 μM) were identified as the most potent inhibitors for yeast α-glucosidase, while compounds 16 (IC₅₀ = 7.7 and 15.6 μM) and 19e (IC₅₀ = 5.1 and 10.4 μM) were the strongest inhibitors of rat intestinal maltase and sucrase. Analysis of the kinetics of enzyme inhibition indicated that 19e inhibited maltase and sucrase in a competitive manner. The results suggest that the aminomethyl-β-d-glucopyranoside moiety can mimic the substrates of α-glucosidase in the enzyme catalytic site, leading to competitive enzyme inhibition. Moreover, the nature of the N-substituent has considerable influence on inhibitory potency.     

Triazinoindole analogs as potent inhibitors of α-glucosidase: Synthesis,biological evaluation and molecular docking studies

A new series of triazinoindole analogs 1–11 were synthesized, characterized by EI-MS and ¹H NMR, evaluated for α-glucosidase inhibitory potential. All eleven (11) analogs showed different range of α-glucosidase inhibitory potential with IC₅₀ value ranging between 2.46 ± 0.008 and 312.79 ± 0.06 μM when compared with the standard acarbose (IC₅₀, 38.25 ± 0.12 μM). Among the series, compounds 1, 3, 4, 5, 7, 8, and 11 showed excellent inhibitory potential with IC₅₀ values 2.46 ± 0.008, 37.78 ± 0.05, 28.91 ± 0.0, 38.12 ± 0.04, 37.43 ± 0.03, 36.89 ± 0.06 and 37.11 ± 0.05 μM respectively. All other compounds also showed good enzyme inhibition. The binding modes of these analogs were confirmed through molecular docking.     

Toward discovery of mutant EGFR inhibitors; Design,synthesis and in vitro biological evaluation of potent 4-arylamino-6-ureido and thioureido-quinazoline derivatives

A new series of 4-anilinoquinazolines with C-6 ureido and thioureido side chains and various substituents at the C-4 anilino moiety was designed, synthesized and evaluated as wild type (WT) and mutant EGFR inhibitors. Most of the compounds inhibited EGFR kinase wild type (EGFR WT) with IC₅₀ values in the low nanomolar range (<0.495–9.05 nM) and displayed more potent cytotoxic effect in BaF/3 expressing EGFR WT than reference compound gefitinib. The anti-proliferative effect of all synthesized compounds against gefitinib insensitive double mutant cell lines Ba/F3 expressing Del19/T790M and Ba/F3 expressing L858R/T790M were assayed. Compounds 4d, 6f, 7e showed significant inhibition (IC₅₀ = 1.76–2.38 μM) in these mutant lines and significant Her2 enzyme inhibition (IC₅₀ = 19.2–40.6 nM) compared to lapatinib (60.1 nM). The Binding mode of compounds 6d, 6f, 7a, 7b and 8b were demonstrated. Furthermore, growth inhibition against gefitinib insensitive cell lines PC9-GR4 (Del19/T790M) were tested, compounds 6f and 7e showed about eight and three folds respectively greater potency than gefitinib. Our structure–activity relationships (SAR) studies suggested that presence of ethyl piperidino urea/thiourea at 6-position and bulky group of (3-chloro-4-(3-fluorobenzyloxy)phenyl)amino at 4-position of quinazoline may serve as promising scaffold for developing inhibitors against wild type and mutant EGFR.