Design, synthesis, and cytotoxicity screening of new synthesized imidazolidine-2-thiones as VEGFR-2 enzyme inhibitors.

A series of imidazolin-2-thione derivatives was synthesized and structurally confirmed through the use of different spectroscopic techniques such as infrared, nuclear magnetic resonance, and mass spectrometry along with elemental analyses. The breast cancer cell line MCF-7 was utilized in the evaluation of the cytotoxic activity of the prepared molecules. The tested molecules 3 and 7 exhibited the best results on MCF-7 cells, with mean IC50 values of 3.26 and 4.31 µM, respectively. The results of the VEGFR-2 assay indicated that compounds 3 and 7 displayed a good inhibition of the VEGFR-2 kinase enzyme. Additionally, DNA flow cytometry of compounds 3 and 7 showed cell cycle arrest at the G0/G1 phase, cell apoptosis, and marked DNA fragmentation in MCF-7 cells. Finally, compounds 3 and 7 were proved to upregulate the activation of effector caspase-3/7, as presented by the caspase-3/7 green flow cytometry assay.

Synthesis, Molecular Docking and Biological Evaluation of 2- Mercaptomidazoles using Solid Phase Synthesis.

BACKGROUND: With the increasing resistance and side effects caused due to antifungal agents there is an urgent need for the new potent antifungal agents with low toxicity profile. Imidazoles have been used against fungal infections since long time. Further, our previous studies demonstrated that mercaptoimidazoles possessed good antifungal potency. AIM AND OBJECTIVE: This study was aimed to study the antifungal potency of new series of 2- mercaptoimidazoles. MATERIALS AND METHODS: Eighteen new 2-mercaptoimidazoles containing substituted phenyl group were synthesized and structures of the synthesized compounds were characterized by spectral studies. The synthesized compounds were screened for their antifungal potency. Compound 2-(1-(3-hydroxyphenyl)-2- mercapto-1H-imidazol-4-yl)phenol was found to be the most potent compound among all synthesized compounds against tested fungal strains. Moreover, all the synthesized compounds were further subjected to molecular docking study for the inhibition of enzyme 14α-demethylase. RESULTS: The in-silico molecular docking study results showed that all the synthesized compounds have minimum binding energy and good affinity for the active site and may be considered as good inhibitor of 14α-demethylase. CONCLUSION: 2-mercaptoimidazoles may be used as potential lead molecules as 14α-demethylase inhibitors.

Molecular Modelling Studies of 1,4-Diaryl-2-Mercaptoimidazole Derivatives for Antimicrobial Potency.

BACKGROUND: Imidazoles are considered as potent antimicrobial agents. In view of this 2-mercaptoimidazoles were synthesized and evaluated for antimicrobial study. METHODS: Some new 2-mercaptoimidazoles 4a-r were synthesized using substituted aniline and substituted phenacyl bromides in the presence of anhydrous sodium carbonate or potassium carbonate and potassium thiocyanate under solvent-free conditions catalyzed by eco-friendly ptoluene sulfonic acid. RESULTS: The structure of compounds was evaluated on the basis of Infrared spectroscopy (IR), 1HNMR (proton nuclear magnetic resonance) and mass spectral studies. These novel compounds were screened for in-vitro antibacterial and antifungal potency against Staphyllococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger. Further, the study was rationalized by molecular modeling studies. All the compounds were subjected to molecular modeling studies for inhibition of enzyme 14α-demethylase. CONCLUSIONS: The compounds were found to be effective in inhibiting the growth of pathogens. The in-silico results depicted that, all the synthesized compounds have minimum binding energy and good affinity towards the active site and thus can be considered as good inhibitors of 14α- demethylase enzyme.

Design of anti-thyroid drugs: Binding studies and structure determination of the complex of lactoperoxidase with 2-mercaptoimidazole at 2.30 Å resolution.

Lactoperoxidase (LPO) belongs to mammalian heme peroxidase superfamily, which also includes myeloperoxidase (MPO), eosinophil peroxidase (EPO), and thyroid peroxidase (TPO). LPO catalyzes the oxidation of a number of substrates including thiocyanate while TPO catalyzes the biosynthesis of thyroid hormones. LPO is also been shown to catalyze the biosynthesis of thyroid hormones indicating similar functional and structural properties. The binding studies showed that 2-mercaptoimidazole (MZY) bound to LPO with a dissociation constant of 0.63 µM. The inhibition studies showed that the value of IC50 was 17 µM. The crystal structure of the complex of LPO with MZY showed that MZY bound to LPO in the substrate-binding site on the distal heme side. MZY was oriented in the substrate-binding site in such a way that the sulfur atom is at a distance of 2.58 Å from the heme iron. Previously, a similar compound, 3-amino-1,2,4-triazole (amitrole) was also shown to bind to LPO in the substrate-binding site on the distal heme side. The amino nitrogen atom of amitrole occupied the same position as that of sulfur atom in the present structure indicating a similar mode of binding. Recently, the structure of the complex of LPO with a potent antithyroid drug, 1-methylimidazole-2-thiol (methimazole, MMZ) was also determined. It showed that MMZ bound to LPO in the substrate-binding site on the distal heme side with 2 orientations. The position of methyl group was same in the 2 orientations while the positions of sulfur atom differed indicating a higher preference for a methyl group.

Molecular Modeling Investigation of Some New 2-mercaptoimidazoles.

BACKGROUND: Docking study has become an important and interesting tool for the investigation of drug- receptor interaction. Computational methodologies have become a crucial component in the drug discovery programs which involves identification of target and lead along with their ADME and pharmacokinetic studies so as to obtain a potent lead. OBJECTIVE: Synthesis and Molecular modeling investigation of some new 2-mercaptoimidazoles. METHOD: New 2- mercaptoimidazoles were synthesized via solid phase synthesis and were characterized by spectral studies i.e IR, 1NMR, Mass spectra and LC-MS. Compounds were screened for their antimicrobial potency via agar well diffusion assay against three bacterial strains and two fungal strains. Compounds were subjected to molecular docking studies for rationalization of their mode of action. RESULTS: 18 new imidazole derivatives having mercapto group (4a-r) were synthesized via solid phase synthesis and were characterized by spectral studies i.e IR, 1NMR, Mass spectra and LC-MS. All the compounds were found to possess promising antimicrobial potency. However, compounds 4j and 4k were found to be the most potent compounds of the series against al the tested strains. The in silcio molecular modeling study results indicated that all the compounds exhibited good affinity towards the active site and thus may be considered as good inhibitors of enzyme 14α.-demethylase. CONCLUSION: Thus, it may be concluded that the compounds are good inhibitors of enzyme 14α.- demethylase and may be further investigated to obtain antimicrobial lead.

Synthetic Lethality of a Novel Small Molecule Against Mutant KRAS-Expressing Cancer Cells Involves AKT-Dependent ROS Production.

AIMS: We recently reported the death-inducing activity of a small-molecule compound, C1, which triggered reactive oxygen species (ROS)-dependent autophagy-associated apoptosis in a variety of human cancer cell lines. In this study, we examine the ability of the compound to specifically target cancer cells harboring mutant KRAS with minimal activity against wild-type (WT) RAS-expressing cells. RESULTS: HCT116 cells expressing mutated KRAS are susceptible, while the WT-expressing HT29 cells are resistant. Interestingly, C1 triggers activation of mutant RAS, which results in the downstream phosphorylation and activation of AKT/PKB. Gene knockdown of KRAS or AKT or their pharmacological inhibition resulted in the abrogation of C1-induced ROS production and rescued tumor colony-forming ability. We also made use of HCT116 mutant KRAS knockout (KO) cells, which express only a single WT KRAS allele. Exposure of KO cells to C1 failed to increase mitochondrial ROS and cell death, unlike the parental cells harboring mutant KRAS. Similarly, mutant KRAS-transformed prostate epithelial cells (RWPE-1-RAS) were more sensitive to the ROS-producing and death-inducing effects of C1 than the vector only expressing RWPE-1 cells. An in vivo model of xenograft tumors generated with HCT116 KRAS(WT/MUT) or KRAS(WT/-) cells showed the efficacy of C1 treatment and its ability to affect the relative mitotic index in tumors harboring KRAS mutant. INNOVATION AND CONCLUSION: These data indicate a synthetic lethal effect against cells carrying mutant KRAS, which could have therapeutic implications given the paucity of KRAS-specific chemotherapeutic strategies. Antioxid. Redox Signal. 24, 781-794.

Exploring the pH dependent SERS spectra of 2-mercaptoimidazole molecule adsorbed on silver nanocolloids in the light of Albrecht's "A" term and Herzberg-Teller charge transfer contribution.

The pH dependent surface-enhanced Raman scattering (SERS) spectra of biologically and industrially significant, 2-mercaptoimidazole (2-MI) molecule at 1.0×10(-10)M concentration have been investigated. The pH dependent SERS spectra are compared with the corresponding normal Raman spectra (NRS) of the molecule. The vibrational analyses of the pH dependent NRS spectra of the molecule reveal that in the acidic pH medium, the cationic form of the molecule is preponderant, while in the neutral pH, the existence of the cationic, normal, ylidic, and anionic forms of the molecule are all prevalent. However, in the alkaline pH medium, the anionic form of the molecule is estimated to be dominant. The SERS spectral analyses suggest the predominant adsorption of the cationic and the normal forms of the molecule on the nanocolloidal silver surface at acidic pH of the medium. However, at neutral pH, the cationic and/or normal, ylidic forms of the molecule take active part in the adsorption process, while considerable interactions of the normal, ylidic and/or anionic forms of the molecule with the nanocolloidal silver surface are presaged at alkaline pH of the medium. The genesis of selective enhancements of the Raman bands in the SERS spectra of the molecule recorded at various pH values of the medium has been unveiled from the view of the Albretcht's "A" and Herzberg-Teller (HT) charge transfer (CT) contribution.

Genesis of enhanced Raman bands in SERS spectra of 2-mercaptoimidazole: FTIR, Raman, DFT, and SERS.

The surface enhanced Raman scattering (SERS) spectra of biologically and industrially significant, 2-mercaptoimidazole (2-MI) molecule have been investigated. The SERS spectra of the molecule at different concentrations of the adsorbate are compared with its Fourier transform infrared (FTIR) and normal Raman spectra (NRS) in varied environments. The optimized molecular structures and vibrational wavenumbers of the various forms (ca. cationic, neutral, ylidic, anionic) of the molecule have been estimated from the density functional theory (DFT). The vibrational signatures of the molecule have been assigned for the first time from the potential energy distributions (PEDs). The analyses of the Raman vibrational signatures reveal the coexistence of all the different forms of the molecule in the solid state and in aqueous solution. Concentration dependent SERS spectra of the molecule at neutral pH of the medium together with the multivariate data analyses techniques also suggest the concomitance of all the probable forms of the molecule in the surface adsorbed state. The genesis of selective enhancements of the Raman bands in the SERS spectra emanating from the cationic, neutral, ylidic and anionic forms of the molecule have been divulged from the view of the Albretcht's "A" and Herzberg-Teller (HT) charge transfer (CT) contribution.

Anxiolytic effects of the MCH1R antagonist TPI 1361-17.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that acts on the MCH1 receptor. MCH1R is expressed widely throughout the brain, particularly in regions thought to be involved in the regulation of stress and emotional response. The role of MCH in anxiety has been controversial, however. Central administration of MCH has been reported to promote or reduce anxiety-like behaviors. The anxiolytic activity of several MCH1R antagonists has also been debated. To address this issue, we have tested whether TPI 1361-17, a highly specific and high affinity MCH1R antagonist, exerts anxiolytic effects in two commonly used models of anxiety, the elevated plus maze and the light-dark transition test. We show that this MCH1R antagonist exerts potent anxiolytic effects in both assays. Our study therefore supports previous studies indicating that MCH1R antagonists may be useful in the treatment of anxiety.

Rhenium(I) tricarbonyl complexes with poly(azolyl)borates generated in situ from an organometallic precursor containing the B-H...Re coordination motif.

Complex fac-[Re(kappa(3)-H(mu-H)(2)B(tim(Me)))(CO)(3)] (1) reacts with protic azoles, like 2-mercapto-1-methylimidazole (tim(Me)H), 2-mercaptobenzothiazole (bztH), or pyrazoles (pz*H), to afford fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(2)(CO)(3)] (2), fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(bzt))(CO)(3)] (3), fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(pz))(CO)(3)] (4), fac-[Re(kappa(3)-HB(tim(Me))(pz)(2))(CO)(3)] (5), and fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(3,5-Me(2)-4-EtOOCCH(2)pz))(CO)(3)] (6). Complexes 2-6 are stabilized by tridentate poly(azolyl)borates generated in situ, and their formation involves most probably a metal-assisted process which is considerably faster for the pyrazole derivatives. The characterization of the novel complexes, 3-6, has been done by common analytical techniques, including single crystal X-ray diffraction analysis. The solid state structures confirmed the presence of hybrid heteroscopionates, presenting (kappa(3)-H, S, S'), (kappa(3)-H, S, N), or (kappa(3)-S, N, N) binding motifs. Multinuclear ((1)H, (13)C, and (11)B) NMR studies have also shown that the coordination mode found in the solid state is retained in solution.

The pharmacological properties of a novel MCH1 receptor antagonist isolated from combinatorial libraries.

Melanin-concentrating hormone (MCH) is a neuropeptide that exhibits potent orexigenic activity. In rodents, it exerts its actions by interacting with one receptor, MCH(1) receptor which is expressed in many parts of the central nervous system (CNS). To study the physiological implications of the MCH system, we need to be able to block it locally and acutely. This necessitates the use of MCH(1) receptor antagonists. While MCH(1) receptor antagonists have been previously reported, they are mainly not accessible to academic research. We apply here a strategy that leads to the isolation of a high affinity and selective MCH(1) receptor antagonist amenable to in vivo analyses without further chemical modifications. This antagonist, TPI 1361-17, was identified through the screening of multiple non-peptide positional scanning synthetic combinatorial libraries (PS-SCL) totaling more than eight hundred thousand compounds in conditions that allow for the identification of only high-affinity compounds. TPI 1361-17 exhibited an IC(50) value of 6.1 nM for inhibition of 1 nM MCH-induced Ca(2+) mobilization and completely displaced the binding of [(125)I] MCH to rat MCH(1) receptor. TPI 1361-17 was found specific, having no affinity for a variety of other G-protein coupled receptors and channels. TPI 1361-17 was found active in vivo since it blocked MCH-induced food intake by 75%. Our results indicate that TPI 1361-17 is a novel and selective MCH(1) receptor antagonist and is an effective tool to study the physiological functions of the MCH system. These results also illustrate the successful application of combinatorial library screening to identify specific surrogate antagonists in an academic setting.

Elucidation of the absolute configuration of JNJ-27553292, a CCR2 receptor antagonist, by vibrational circular dichroism analysis of two precursors.

The absolute configurations of two precursors, that is, 1-(3',4'-dichlorophenyl)-propanol and 1-(3',4'-dichlorophenyl)-propanamine, of a potent 2-mercapto-imidazole CCR-2 receptor antagonist, JNJ-27553292, were determined using vibrational circular dichroism. As a consequence, the absolute configuration of the antagonist itself was also determined. The two precursor compounds were subjected to a thorough conformational analysis and rotational strengths were calculated at the B3LYP/cc-pVTZ level of theory. Based on these data, vibrational circular dichroism spectra were simulated, which in turn were compared with experimental spectra. Agreement between the spectra allowed the assignment of the absolute configuration, which is in agreement with the proposed configuration based on stereospecific reactions on similar compounds.

Using small molecules to overcome drug resistance induced by a viral oncogene.

We used small molecule screening to discover compounds and mechanisms for overcoming E6 oncogene-mediated drug resistance. Using high-throughput screening in isogenic cell lines, we identified compounds that potentiate doxorubicin's lethality in E6-expressing colon cancer cells. Such compounds included quaternary ammonium salts, protein synthesis inhibitors, 11-deoxyprostaglandins, and two additional classes of compounds-analogs of 1,3-bis(4-morpholinylmethyl)-2-imidazolidinethione (a thiourea) and acylated secondary amines that we named indoxins. Indoxins upregulated topoisomerase IIalpha, the target of doxorubicin, thereby increasing doxorubicin lethality. We developed a photolabeling strategy to identify targets of indoxin and discovered a nuclear actin-related protein complex as a candidate indoxin target.

Preconcentration and determination of mercury(II) at a chemically modified electrode containing 3-(2-thioimidazolyl)propyl silica gel.

A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; v = 2.0 mV s(-1) vs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L(-1) was obtained. The detection limit was estimated to be 5 microg L(-1). The precision for six determinations of 0.05 and 0.26 mg L(-1) Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.

2-Mercaptoimidazoles, a new class of potent CCR2 antagonists.

We describe the synthesis and SAR of a new class of CCR2 antagonists based on 2-mercaptoimidazole scaffold. The initial lead 1a was optimized to the 3,4-disubstituted analogues 1p-(S) and 1q-(S), which have IC(50) values in the MCP-1 induced Ca-flux below 0.01 microM.

Octopaminergic agonists for the cockroach neuronal octopamine receptor.

The compounds 1-(2,6-diethylphenyl)imidazolidine-2-thione and 2-(2,6-diethylphenyl)imidazolidine showed the almost same activity as octopamine in stimulating adenylate cyclase of cockroach thoracic nervous system among 70 octopamine agonists, suggesting that only these compounds are full octopamine agonists and other compounds are partial octopamine agonists. The quantitative structure-activity relationship of a set of 22 octopamine agonists against receptor 2 in cockroach nervous tissue, was analyzed using receptor surface modeling. Three-dimensional energetics descriptors were calculated from receptor surface model/ligand interaction and these three-dimensional descriptors were used in quantitative structure-activity relationship analysis. A receptor surface model was generated using some subset of the most active structures and the results provided useful information in the characterization and differentiation of octopaminergic receptor.

Bis(mercaptoimidazolyl)(pyrazolyl)hydroborato complexes of zinc, cadmium, and cobalt: structural evidence for the enhanced tendency of zinc in biological systems to adopt tetrahedral M[S4] coordination.

The bis(2-mercapto-1-methylimidazolyl)(pyrazolyl)hydroborato derivatives [pzBmMe]2Zn, [pzBmMe]2Co, and [pzBmMe]2Cd have been isolated and structurally characterized by X-ray diffraction. Despite their common [pzBmMe]2M composition, each of these complexes adopts a different structure. Thus, (i) the zinc complex exhibits a tetrahedral Zn[S4] structure in which only the sulfur donors coordinate to zinc, (ii) the cobalt complex exhibits a trigonal-bipyramidal Co[S3NH] structure in which one of the pyrazolyl groups and one of the B-H groups coordinate to cobalt, and (iii) the cadmium complex exhibits a six-coordinate Cd[S4H2] structure in which both B-H groups interact with the cadmium center. These comparisons emphasize that zinc has a greater preference for tetrahedral M[S4] coordination than does either cobalt or cadmium, an observation that is in accord with the prevalent role of zinc in the structural sites of enzymes.

Relationship of mitochondrial function and cellular adenosine triphosphate levels to pMC540 and merodantoin cytotoxicity in MCF-7 human breast cancer cells.

In previous studies we have reported that preactivated merocyanine 540 (pMC540) and its chemically synthesized isolates merocil and merodantoin mediate their preferential cytotoxicity towards certain types of malignant cells including human breast cancer cells in vitro and in vivo. The mechanism of cytotoxic action appears to be, in part, via initial interaction with topoisomerase II leading to apoptosis. To further build upon these findings we now show that pMC540 and merodantoin disrupt mitochondrial morphology and function in intact MCF-7 human breast cancer cells as seen by their causing the release of rhodamine 123 from prestained cells, a rapid reduction in ATP levels, inhibition of succinate dehydrogenase activity and oxygen consumption. These data suggest that mitochondria may also be an important target for the cytotoxic action of pMC540 and merodantoin mediated through disruption of the energy balance.

Correlation between DNA topoisomerase II activity and cytotoxicity in pMC540 and merodantoin sensitive and resistant human breast cancer cells.

We have shown previously that preactivated merocyanine 540 (pMC540) and merodantoin appear to mediate their cytotoxic effects via interaction with Topo II. Now, we demonstrate a correlation between DNA Topo II activity and drug-sensitive (MCF-7) and -insensitive (MDA-MB-231) breast cancer cell lines. Further studies indicate that MDA-MB-231 cells are insensitive to the cytotoxic and DNA cleavage effects of pMC540 and merodantoin. This loss of sensitivity is not associated with M(r) 170,000 P-glycoprotein over expression. However, in drug insensitive cells, the Topo II catalytic activity in crude nuclear extract was reduced two- to-three-fold and in cellular extracts was virtually absent as determined by decatenation of kDNA. Topoisomerase I activities appeared similar in extracts from MCF-7 and MDA-MB-231 cell lines. Drug-induced DNA cleavage was reduced two-to-threefold in nuclear extracts from MDA-MB-231. m-AMSA was more effective in inhibiting the decatenation activity in the nuclear extracts from MDA-MB-231 as compared to MCF-7 cells. Western blot analysis of whole-cell lysates revealed undetectable immunoreactivity of Topo II in the drug-insensitive cells. These data indicate that insensitivity of MDA-MB-231 to pMC540 and merodantoin is in part due to the reduced drug-induced formation of the cleavage complex and Topo II (170 kD) enzyme content.

Growth inhibitory effects of pMC540 and merodantoin on established MCF-7 human breast tumor xenografts.

The effect of preactivated merocyanine 540 (pMC540) and one of its chemically synthesized active isolate merodantoin on established human MCF-7 human breast tumor xenografts was investigated. Preactivation is a novel photochemical method for the production of chemotherapeutic compounds that exert their biological effects independent of light. These compounds thus produced, are cytotoxic to human breast cancer cells in vitro and in vivo but only minimally cytotoxic towards normal cells. Nude mice bearing established breast tumors (with or without exogenous estradiol) received injections of pMC540 (250 mg/kg) or merodantoin (75 mg/kg) with or without concurrent treatment with tamoxifen. Treatment with pMC540 and merodantoin caused a 74% and 84% inhibition of tumor growth respectively. Combination of these drugs with tamoxifen did not produce a significant enhancement of growth inhibition. In the absence of exogenous estradiol, identical treatment with pMC540 and merodantoin resulted in 41% and 25% inhibition of tumor growth respectively. Both agents caused a significant (59%) inhibition of growth of estrogen independent human breast tumors established from MDA-MB-435 cells. These results show that photochemically generated novel compounds in pMC540 are effective in suppressing the growth of established human MCF-7 and MDA-MB-435 breast tumor xenografts.