Synthesis, spectral characterization, molecular modeling, antibacterial and antioxidant activities and stability study of binuclear Pd(II) and Ru(III) complexes with novel bis-[1-(2-[(2-hydroxynaphthalen-1-yl)methylidene]amino}ethyl)-1-ethyl-3-phenylthiourea] ligand: Application to detection of cholesterol.

A novel bis-[1-(2-[(2-hydroxynaphthalen-1-yl) methylidene]amino}ethyl)-1-ethyl-3-phenylthiourea] Schiff base (L) and its binuclear palladium and ruthenium complexes have been prepared and characterized by ESI-MS, elemental analysis, NMR (1H NMR, 13C NMR, COSY, NEOSY and HSQC), FT-IR, ATR, UV-Visible spectra, TGA measurements, conductivity and cyclic voltammetry. The experimental results and the molecular parameters calculated using DFT method revealed a square planar geometry around Pd and octahedral geometry around ruthenium metal. The antibacterial activity of the ligand L and its complexes was evaluated against different human bacteria. In addition, the formation constants of the synthesized Schiff base-metal complexes and the systems formed with these chelates and cholesterol were estimated using spectrophotometric technique. The detection of cholesterol using novel Pd and Ru Schiff base complexes was studied using fluorometric method, and the measurements showed that the sensitive fluorometric response towards cholesterol analysis was determined using palladium complex. The limit of detection (LOD) of cholesterol calculated using this complex (4.6 µM) is lower (better) than LOD found using ruthenium complex (19.1 µM) and different compounds previously published around linear range of 0-5 mM.

Synthesis, X-ray, NMR, FT-IR, UV/vis, DFT and TD-DFT studies of N-(4-chlorobutanoyl)-N'-(2-, 3- and 4-methylphenyl)thiourea derivatives.

A new isomers of thiourea derivatives, namely N-(4-chlorobutanoyl)-N'-(2-methylphenyl)-thiourea (1a), N-(4-chlorobutanoyl)-N'-(3-methylphenyl)thiourea (1b) and N-(4-chlorobutanoyl)-N'-(4-methylphenyl)thiourea (1c) have been synthesized by refluxing mixture of equimolar amounts of 4-chlorobutanoylisothiocyanate with 2, 3 or 4-toluidine, respectively. The three isomers were characterized by spectroscopic (UV/vis, FT-IR and NMR) and X-ray crystallography techniques. To investigate the isomerization effect on spectroscopic data, DFT and TD-DFT calculations have been carried out using five hybrid functionals (B3LYP, B3P86, CAM-B3LYP, M06-2X and PBE0) to predict UV/vis absorption bands (n→π∗ and π→π∗), (1)H and (13)C NMR chemical shifts, FT-IR vibration modes and X-ray parameters (bonds, bond angles and torsion angles) for 1a, 1b and 1c isomers. The results showed that the isomerization effect is significant on λ(MAX) absorption bands, while for IR and NMR the effect is negligible. In accordance with previous studies, B3LYP, B3P86 and PBE0 gave the most reliable to predict the excitation energies of thiourea derivatives.

Development of a Nile-blue based chemodosimeter for Hg2+ in aqueous solution and its application in biological imaging.

A Nile blue-based chemodosimeter was newly synthesized. It can detect Hg(2+) in aqueous solution based on desulfurization reaction. Upon its addition into aqueous Hg(2+) ion solution, it exhibited a considerable blue-shift in its absorption and obvious fluorescence quenching. The detection mechanism was proved by mass spectrometry analysis and Gaussian calculations. Detection at an emission of 685 nm was extremely sensitive, with a detection limit of 2.5 × 10(-9) mol/L. The fluorescent images in living cells and zebrafish demonstrate its potential for studying the accumulation of mercury species in organism.

Recycling and refurbishing old antitubercular drugs: the encouraging case of inhibitors of mycolic acid biosynthesis.

One of the first approaches undertaken in the quest for antitubercular compounds was that of understanding the mechanism of action of old drugs and proposing chemical modifications or other strategies to improve their activity, generally lost to the mechanisms of resistance developed by Mycobacterium tuberculosis. A leading case was the work carried out on a set of compounds with proven activity on the essential pathway of the synthesis of mycolic acids. As a result, different solutions were presented, improving the activity of those inhibitors or producing novel compounds acting on the same molecular target(s), but avoiding the most common resistance strategies developed by the tubercle bacilli. This review focuses on the activity of those compounds, developed following the completion of the studies on several of the classic antitubercular drugs.

Histone deacetylase activators: N-acetylthioureas serve as highly potent and isozyme selective activators for human histone deacetylase-8 on a fluorescent substrate.

We report, for the first time, that certain N-acetylthiourea derivatives serve as highly potent and isozyme selective activators for the recombinant form of human histone deacetylase-8 in the assay system containing Fluor-de-Lys as a fluorescent substrate. The experimental data reveals that such activating feature is manifested via decrease in the K(m) value of the enzyme's substrate and increase in the catalytic turnover rate of the enzyme.

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 IC(50) value of 2.7 microM in inhibition of melanogenesis. The structure for potent inhibitory activity of these derivatives are required with the direct connection of pi-planar structure to thiourea without steric hinderance in PTU derivatives and the hydrophobic substituent at para position in case of semicarbazones.

Nanomolar Hg(II) detection using Nile blue chemodosimeter in biological media.

A Nile blue-based chemodosimeter (1) was newly synthesized, and its application for detection of the Hg(2+) ion in 100% aqueous solution was demonstrated. Upon its addition into aqueous Hg(2+) ion solution, it exhibited a considerable blue-shift in its absorption and emission spectra, driven by a desulfurization reaction. Detection at an emission of 652 nm was extremely sensitive (less than 1.0 ppb), even in biological media such as blood plasma and albumin.

Synthesis and anticonvulsant activity of new N-(alkyl/sub-stituted aryl)-N'-[4-(5-cyclohexylamino)-1,3,4-thiadiazole-2-yl)phenyl]thioureas.

A series of novel thiourea derivatives carrying the 5-cylohexylamino-1,3,4-thiadiazole moiety was synthesized and their anticonvulsant activity was evaluated. Structures of the synthesized compounds have been confirmed by IR, 1H-NMR, and elemental analysis. All of the compounds were administered at a dose of 50 mg/kg. Some of the active compounds have different effects in pentylenetetrazole (PTZ) and maximal electroshock (MES) tests, indicating the therapeutical potential in petit mal seizures, but not in grand mal seizures. Compounds 10, 11, 13, and 14 carrying 2-methylphenyl, 4-chlorophenyl, allyl, and 4-methylphenyl on the thiourea pharmacophore, increased the survival rate in the PTZ model. The ED50 values of the active compounds 10, 11, 13, and 14 were found 68.42, 43.75, 18.75 and 25 mg/kg, respectively.

Synthesis and in vitro antitubercular activity of some 1-[(4-sub)phenyl]-3-(4-{1-[(pyridine-4-carbonyl)hydrazono]ethyl}phenyl)thiourea.

Various isonicotinyl hydrazones were prepared by reacting isonicotinyl hydrazide [INH] with 1-(4-acetylphenyl)-3-[(4-sub)phenyl]thiourea and were tested for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv and INH-resistant M. tuberculosis using the BACTEC 460 radiometric system. Among the synthesized compounds, 1-(4-fluorophenyl)-3-(4-{1-[(pyridine-4-carbonyl)-hydrazono]ethyl}phenyl)thiourea (4d) was found to be the most potent compound with a minimum inhibitory concentration of 0.49 microM against M. tuberculosis H37Rv and INH-resistant M. tuberculosis. When compared to INH, 4d was found to be 3 and 185 times more active against M. tuberculosis H37Rv and INH-resistant M. tuberculosis, respectively, with a selectivity index of >300.

Biological evaluation of 1-alkyl-3-phenylthioureas as orally active HDL-elevating agents.

A series of 1-alkyl-3-phenylthiourea analogues were prepared and evaluated as HDL- and Apo A-I-elevating and triglyceride-lowering agents. Several derivatives were superior to gemfibrozil. The optimal analogue (HDL376) was shown to raise HDL cholesterol in the rat, hamster, dog, and monkey models.

1-Benzhydryl-3-phenylurea and 1-benzhydryl-3-phenylthiourea derivatives: new templates among the CB1 cannabinoid receptor inverse agonists.

New 1-benzhydryl-3-phenylurea derivatives and their 1-benzhydryl-3-phenylthiourea isosteres were synthesized and evaluated for their human CB1 and CB2 cannabinoid receptor affinity. These compounds proved to be selective CB1 cannabinoid receptor ligands, acting as inverse agonists in a [35S]-GTPgammaS assay. The affinity of 3,5,5'-triphenylimidazolidine-2,4-dione and 3,5,5'-triphenyl-2-thioxoimidazolidin-4-one derivatives, possessing the 1-benzhydryl-3-phenylurea and 1-benzhydryl-3-phenylthiourea moiety, respectively, was also evaluated. In conclusion, the 1-benzhydryl-3-phenylurea scaffold seems to be a new interesting template of CB1 cannabinoid receptor inverse agonists.

1-Hydroxyalkyl-3-phenylthioureas as novel HDL-elevating agents.

A series of 1-hydroxyalkyl-3-phenylthiourea analogs were prepared and evaluated as HDL-and Apo A-I-elevating agents. Derivatives 5h, 7j, 7n, and 7o were found to be as effective or superior to gemfibrozil.

Analysis of structure-activity relationships with the N-(3-acyloxy-2-benzylpropyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea template for vanilloid receptor 1 antagonism.

In a continuing effort to elucidate the structure-activity relationships of the lead antagonist N-[2-(3,4-dimethylbenzyl)-3-pivaloyloxypropyl]-N'-[4-(methylsulfonylamino)benzyl]thiourea (1), the distances between the proposed four pharmacophores in 1 have been varied by insertion or deletion of one carbon to optimize their fit to the receptor. In addition, the acyloxy group of the C region was replaced with amide and N-hydroxy amide to identify the pharmacophoric importance of the ester group in the C2 region. The results indicated that the pharmacophoric arrangement of 1 was optimal for receptor binding affinity and antagonism, and the ester of the C2 region was significant for receptor binding. Among the derivatives, compound 19 showed distinct behavior with a 2-fold improvement in antagonism but a 13-fold reduction in binding affinity compared to 1. The partial separation of pharmacophoric requirements of these two assays has been noted before and compound 19 is thus selective for the calcium entry-linked receptor population. The conformational analysis of 1 generated three distinct conformers having different types of hydrophobic interactions, which will be utilized for exploring the active conformation of the VR1 ligand.

2-Nitrophenylcarbamoyl-(S)-prolyl-(S)-3-(2-naphthyl)alanyl-N-benzyl-N - methylamide (SDZ NKT 343), a potent human NK1 tachykinin receptor antagonist with good oral analgesic activity in chronic pain models.

A lead compound which had sub-micromolar affinity for the rabbit NK1 receptor but negligible affinity for rat NK1 receptors, 3a, was discovered by directed screening. 2-Substitution in the ring of the benzylthiourea substituent in the initial lead was found to be important, and halogens (Cl, Br) in this position were found to improve affinity for the human receptor. The activity of a series of 2-halo-substituted benzylthioureas was then optimized by modification of the proline diphenylmethyl amide, guided by a simple conceptual model based on structural overlay between these early antagonists and NK1 selective peptides. In this way, aromatic amino acid amides were identified which had improved affinity with respect to the starting diphenylmethyl (DPM) amides. The first sub-nanomolar ligand for the human NK1 receptor which arose from this series, 4af, combined a 2-chlorobenzylthiourea unit with a 2-naphthylalanine amide. Contemporaneously it was discovered that the benzylthiourea unit could be simplified to a phenylthiourea providing that an appropriate 2-substituent was also incorporated. Combination of these two series gave 2-NO2 phenylthiourea analogues which led directly to the analogous urea, 5f (2-nitrophenylcarbamoyl-(S)-prolyl-(S)-3-(2-naphthyl)alanyl-N-benz yl- N-methylamide, SDZ NKT 343), a highly potent ligand for the human NK1 receptor (Ki = 0.16 nM). In addition to its high in vitro potency, 5f proved to be a potent orally active analgesic in guinea pig models of chronic inflammatory and neuropathic pain. The nature of the 2-aryl substituent was found to be critical for oral activity in this series. Clinical evaluation of 5f as a novel analgesic agent is currently underway.

1-Acyl-, 3-acyl- and 1,3-diacyl-3-furfuryl-1-phenylthioureas with platelet antiaggregating and other activities.

The synthesis in excellent yields of 1-acyl-3-furfuryl-1-phenylthioureas 2 by reacting at t less than or equal to 10 degrees C 3-furfuryl-1-phenylthiourea 1, prepared in situ from furfurylamine and phenyl isothiocyanate, with aromatic or heterocyclic acyl chlorides in pyridine solution is described. 1-Acylthioureas 2 rearranged in high yields to 3-acylthioureas 3 by treatment with sodium hydroxide in heterogeneous phase. 1,3-Diacyl-3-furfuryl-1-phenylthioureas 4 were obtained in satisfactory yields by treatment of 1 with two moles of acyl chloride as in the case of 1-monoacylation. The thiourea 1 prepared in situ reacted with iodomethane in dimethylformamide solution and in the presence of sodium hydride to give in high yield the S-methyl derivative, namely the methyl ester of N-phenyl-1-furfurylaminethiocarboximidic acid. Some acylthioureas 2 and 4 showed a platelet antiaggregating activity in vitro superior or comparable to that of acetylsalicylic acid. The 1,3-diacylthiourea 4 c exhibited an appreciable anticonvulsant activity in mice and some compounds 2 and 4 moderate competitive antiacetylcholine and H1-antihistamine effects in vitro.

3,3-disubstituted 1-acyl-1-phenylthioureas with platelet antiaggregating and other activities.

This paper describes the synthesis in excellent yields of N-acyl-N-phenyl-1-pyrrolidine-, 1-piperidine-, 4-morpholine-, 1,2,3,4-tetrahydro-1-quinoline-, 1,2,3,4-tetrahydro-2-isoquinoline-, 10-phenothiazine- and 2,2'-dipyridylamine-carbothioamides by reaction of the corresponding 3,3-disubstituted 1-phenylthioureas, prepared in situ from the appropriate secondary amine and phenylisothiocyanate, with aromatic or heterocyclic acyl chlorides in pyridine solution or, in lower yields, in anhydrous dimethylformamide or pyridine solution in the presence of sodium hydride. N-phenyl-1-pyrrolidinecarbothioamide prepared in situ reacted with iodomethane in dimethylformamide solution and in the presence of sodium hydride to give excellent yield of the S-methyl derivative, namely the methyl ester of N-phenyl-1-pyrrolidinethiocarboximidic acid. Some of the above compounds, in particular the phenothiazine acylthioureas, showed platelet antiaggregating activity in vitro superior or comparable to that of acetylsalicylic acid; moreover, some acylthioureas exhibited moderate hypoglycemic activity in rats and competitive antiacetylcholine and H1-antihistaminic effect in vitro inferior to that of atropine and chlorpheniramine, respectively.

Synthesis of a series of new N1-[4-(4-nitrophenylthio)phenyl]-N3-(H/alkyl/acyl/aryl) thioureas and their antifungal, insecticidal and larvicidal activities.

A series of new mono and disubstituted thioureas, derived from 4-(4-nitrophenylthio) aniline, have been prepared and screened for antifungal activity against Alternaria alternata and Curvularia lunata. Their insecticidal and larvicidal activities have also been evaluated against adult male and female cockroaches (Periplanata americana) and mosquito larvae (Culex pipiens fatigans Wied) of IIIrd and early IVth instar stage, respectively. The tabulated results reveal that most of the thiourea derivatives, in general, possess marked antifungal, insecticidal and larvicidal properties, but the chlorosubstituted derivatives, in particular, are the most active compounds in the entire series. Compound 20, N1-[4-(4-nitrophenylthio)phenyl]-N3-(4-chlorophenyl) thiourea, was the most active antifungal compound, whereas, compound 12, N1-[4-(4-nitrophenylthio)phenyl]-N3-(4-chlorobenzoyl) thiourea, was the most potent insecticidal and larvicidal compound.

Antihypertensive (2-aminoethyl)thiourea derivatives. 1.

Structure-activity studies were carried out on a series of antihypertensive 1-(2-aminoethyl)-3-(substituted phenyl)thioureas. From this class of compounds, the 2,6-dichlorophenyl analogue 2 was found to have potent oral antihypertensive activity in two hypertensive rat models and the renal hypertensive dog. In addition to its effect on blood pressure, 2 displayed sedative effects which had a marked species specificity.