Design, synthesis, and mechanistic insight of novel imidazolones as potential EGFR inhibitors and apoptosis inducers.

As regards to the structural analysis and optimization of diverse potential EGFR inhibitors, two series of imidazolyl-2-cyanoprop-2-enimidothioates and ethyl imidazolylthiomethylacrylates were designed and constructed as potential EGFR suppressors. The cytotoxic effect of the prepared derivatives was assessed toward hepatic, breast, and prostate cancerous cells (Hep-G2, MCF-7, and PC-3). Three derivatives 3d, 3e, and 3f presented potent antiproliferative activity and selectivity against the examined tumor cells showing IC50 values at low micromolar levels. Hence, successive biological assays were applied to determine the probable mechanism of action of the new compounds. They exhibited significant EGFR suppression with an IC50 range of 0.137-0.507 µM. The most effective EGFR inhibitor 3f arrested the MCF-7 cell cycle at the S phase by inducing the apoptotic pathway that was confirmed via increasing the expression of Caspases 8, 9, and Bax, which are associated with Bcl-2 decline. Additionally, molecular docking displayed a distinctive interaction between 3f and EGFR binding pocket. Overall, this work introduces some novel imidazolyl-2-cyanoprop-2-enimidothioates and ethyl imidazolylthiomethylacrylates as potential cytotoxic and EGFR inhibitors that deserve further research in tumor therapy.

Potent Antitumour Effects of Novel Pentabromobenzylisothioureas Studied on Human Glial-derived Tumour Cell Lines.

BACKGROUND/AIM: Tumours of astroglial origin are the most common primary brain malignancy characterized by infiltrative growth and resistance to standard antitumour therapy. Glioma progression is thought to be related to various intracellular signal transduction pathways that involve the activation of protein kinases. Protein kinases play important roles in cell differentiation, proliferation, and survival. Recently, novel, specific inhibitors of constitutively active serine/threonine kinases and structurally similar isothiourea derivatives were suggested to induce apoptosis and inhibit proliferation in several types of human cancer cells. MATERIALS AND METHODS: In this study, we examined the cytotoxic and proapoptotic activities of selected modified pentabromobenzyl isothioureas (ZKKs) in an adult human glioblastoma (T98G) and a subependymal giant cell astrocytoma cell (SEGA) line. We evaluated cell proliferation, viability, and apoptosis. RESULTS: Two pentabromobenzyl isothiourea bromide derivatives, ZKK-13 and N,N,N'-trimethyl-ZKK1 (TRIM), exhibited the most potent cytotoxic and proapoptotic efficacies against human glioma-derived cells, even at a very low concentration (1 µM). ZKK-13 (25-50 µM) inhibited cell growth by approximately 80-90% in 24 and 48 h of treatment. We showed that selected ZKKs exerted antiproliferative activity against astroglial neoplastic cells of both low- and high-grade tumour malignancy classes. No synergistic effects were detected when ZKKs were combined with serine/threonine kinase inhibitors. CONCLUSION: Our findings indicated that modified ZKKs show promise for the treatment of glioma-derived brain tumours.

Allylic isothiouronium salts: The discovery of a novel class of thiourea analogues with antitumor activity.

A series of 28 aryl- and alkyl-substituted isothiouronium salts were readily synthesized in high yields through the reaction of allylic bromides with thiourea, N-monosubstituted thioureas or thiosemicarbazide. The S-allylic isothiouronium salts substituted with aliphatic groups were found to be the most effective against leukemia cells. These compounds combine high antitumor activity and low toxicity toward non-tumoral cells, with selectivity index higher than 20 in some cases. Furthermore, the selected isothiouronium salts induced G2/M cell cycle arrest and cell death, possibly by apoptosis. Therefore, these compounds can be considered as a promising class of antitumor agents due to the potent cytostatic activity associated with high selectivity.

Synthesis and characterization of crosslinked polyisothiouronium methylstyrene nanoparticles of narrow size distribution for antibacterial and antibiofilm applications.

BACKGROUND: Isothiouronium salts are well known in their variety of antimicrobials activities. The use of polymeric biocides, polymers with antimicrobial activities, is expected to enhance the efficacy of some existing antimicrobial agents, thus minimizing the environmental problems accompanying conventional antimicrobials. METHODS: The current manuscript describes the synthesis and characterization of crosslinked polyisothiouronium methylstyrene (PITMS) nanoparticles (NPs) of narrow size distribution by dispersion co-polymerization of the monomer isothiouronium methylstyrene with the crosslinking monomer ethylene glycol dimetacrylate. RESULTS AND DISCUSSION: The effect of total monomer, crosslinker and initiator concentrations on the size and size distribution of the formed NPs was also elucidated. The bactericidal activity of PITMS NPs of 67 ± 8 nm diameter was illustrated for 4 bacterial pathogens: Listeria innocua, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. In order to demonstrate the potential of these PITMS NPs as inhibitor of biofilm formation, polyethylene terephthalate (PET) films were thin-coated with the PITMS NPs. The formed PET/PITMS films reduced the viability of the biofilm of Listeria by 2 orders of magnitude, making the coatings excellent candidates for further development of non-fouling surfaces. In addition, PITMS NP coatings were found to be non-toxic in HaCaT cells. CONCLUSIONS: The high antibacterial activity and effective inhibition of bacterial adsorption indicate the potential of these nanoparticles for development of new types of antibacterial and antibiofilm additives.

Inverse neighboring group participation: explanation of an unusual S→N alkyl migration of isothiuronium salts containing a lactone group.

A detailed experimental and DFT study of the S to N alkyl migration of substituted S-(1(3H)-isobenzofuranon-3-yl)isothiuronium bromide to N,N'-dimethyl-N-(3-oxo-1,3-dihydro-2-benzofuran-1-yl)thiourea provided evidence for the existence of an unusual double displacement mechanism involving two consecutive back-side S(N)2 reactions where a carboxylate anion has a crucial role both as a leaving group as well as an internal nucleophile. The thiazetidine zwitterionic species that is involved in this mechanism as an intermediate was characterized by infrared multiphoton dissociation spectroscopy and was trapped with methyl iodide. It was found that the intermediate has a structure of a free ion pair. The double-displacement mechanism can be considered as a new type of inverse lactone neighboring group participation.

Synthetic studies on novel 1,4-dihydro-2-methylthio-4,4,6-trisubstituted pyrimidine-5-carboxylic acid esters and their tautomers.

A mixture of alkyl 1,4-dihydro-2-methylthio-4,4,6-trisubstituted pyrimidine-5-carboxylate 1 and its tautomeric isomer, alkyl 1,6-dihydro-2-methylthio-4,6,6-trisubstituted pyrimidine-5-carboxylate 2 is synthesized by the Atwal-Biginelli cyclocondensation reaction of S-methylisothiourea hemisulfate salt 3 with 2-(gem-disubstituted)methylene-3-oxoesters 4 that can be accessed by the Lehnert procedure for the Knoevenagel-type condensation. The structures of the tautomeric products of the Atwal-Biginelli cyclocondensation reaction, 1 and 2, which are inseparable from each other, are determined unambiguously by (1)H-NMR spectroscopy at various temperatures and nuclear Overhauser enhancement spectroscopy (NOESY) experiment. Because these dihydropyrimidine products are otherwise inaccessible and thus hitherto unavailable, the synthetic methods established in this study will help to expand the molecular diversity of their related derivatives.

Fluorescence sensing of phytate in water using an isothiouronium-attached polythiophene.

A water-soluble isothiouronium-attached polythiophene (1(poly)) is prepared for the first time by the oxidative polymerization of 3-(3-(N-(2-methoxyethoxy)ethyl-N-methyl-S-isothiouronio)propoxy-4-methylthiophene (1) with FeCl(3). The gel-permeation chromatography analysis allows us to estimate the number average molecular weight (M(n)) and the polydispersity index (PDI) to be 5.68x10(5) and 1.4, respectively. The polymers (excited at 438 nm) show an absorption band at 438 nm and fluorescence at 546 nm, with 1.2 % fluorescence quantum yield when fluorescein was used as a reference. The pH-dependent absorption spectra at varying pH, indicates that aggregation starts at neutral conditions. At pH 5.5, 1(poly) exhibits a significant quenching in the fluorescence upon the addition of phytate (IP(6)), as a plausible analyte. This response is higher than that in the case of other anions such as adenosine 5-triphosphate (ATP), pyrophosphate (PPi), cis,cis-1,3,5-cyclohexanetriol triphosphate (CTP(3)), and H(2)PO(4)(-). As inferred from the SEM measurement, the phytate-induced spectral change has been explained on the basis of the pi-stacked aggregation of the polymer.

Surface and biocidal activity of some synthesized metallo azobenzene isothiouronium salts.

A novel series of azobenzene isothiouronium salts of different alkyl chains (propyl, hexyl and dodecyl) were synthesized by reaction of 4-((4-methylphenyl)azo)phenol with 1,3-dibromopropane, 1,6-dibromohexane and 1,12-dibromododecane, respectively. These salts were reacted with copper (II) halide to give their corresponding metallo complexes. The surface tension measurements for the synthesized compounds show that the metallo complexes have adsorption and micellization better than that of the parent azobenzene isothiouronium salts. The pathogenic Gram-negative bacteria, Gram-positive bacteria, fungi and yeast were used to determine the biocidal activity of these compounds using gradient plate technique. The results indicate that the copper complexes of the synthesized azobenzene isothiouronium salts have a relatively better biocidal activity than the parent salts.

Controlled template-assisted assembly of plasmid DNA into nanometric particles with high DNA concentration.

A series of novel cationic detergents that contain cleavable hydrophilic isothiuronium headgroups was synthesized, and their utility in controlled assembly of plasmid DNA into small stable particles with high DNA concentration investigated. The detergents have alkyl chains of C(8)-C(12) and contain hydrophilic isothiuronium headgroups that give relatively high critical micelle concentration (CMC) to the detergents (>10 mM). The isothiuronium group masks a sulfhydryl group on the detergent and can be cleaved in a controlled manner under basic conditions to generate a reactive thiol group. The thiol group can undergo a further reaction after the detergents have accumulated on a DNA template to form a disulfide-linked lipid containing two alkyl chains. The pH-dependent kinetics of cleavage of the isothiuronium group, the CMC of the surfactants, the formation of the complexes, and the transfection efficiency of the DNA complexes have been investigated. Using the C(12) detergent, a approximately 6 kilo-basepair plasmid DNA was compacted into a small particle with an average diameter of around 40 nm with a approximately -13 mV zeta-potential at high DNA concentration (up to 0.3 mg/mL). The compounds were well tolerated in cell culture and showed no cytotoxicity under their CMCs. Under appropriate conditions, the small particle retained transfection activity.

Novel histamine H3 receptor antagonists: synthesis and evaluation of formamidine and S-methylisothiourea derivatives.

In order to obtain a new, potent and selective histamine H3 receptor antagonists, chemical modifications of thioperamide, a well-known H3 receptor antagonist, were conducted. A new series of compounds has been synthesized by modifying the thiourea and cyclohexyl groups of thioperamide, and tested for H3 affinity by receptor binding assay using plasma membrane from rat cerebral cortex. The thiourea group of thioperamide was found to be replaceable with a basic moiety such as formamidine or S-methylisothiourea. Replacement of the cyclohexyl group in thioperamide by a 1-adamantyl or an exo-2-norbornyl group increased the affinity for H3 receptor. Among the compounds synthesized, N-(1-adamantyl)-N',N'-[3-(4(5)-1H-imidazolyl)pentamethylene] formamidine 3f (AQ0145) showed the highest H3 receptor affinity, having a potent antagonistic activity. This compound was at least 1,000-fold more active towards H3 than towards H1 and H2 receptors.

S-aryl (tetramethyl) isothiouronium salts as possible antimicrobial agents, IV.

The 1-octanol/water partition coefficients of a series of antimicrobial S-aryl(tetramethyl)isothiouronium salts, were determined. The concentration of the solute in the two phases was measured by means of HPLC. The values of the hydrophobic parameters thus obtained were correlated to the corresponding capacity factors (log Kw) and compared with those expected on the basis of additive-constitutive principles. The deviations were interpreted quantitatively on the basis of electronic interactions of the substituents in the benzene ring. Equations correlating structural features and antimicrobial activity of some studied compounds by means of molecular parameters were formulated.

Thioureas and isothiouronium salts of the aglycone of teicoplanin. I. Synthesis and biological activity.

A series of thiourea and isothiouronium salt derivatives of the aglycone of teicoplanin was prepared by reaction of the terminal amino group with isothiocyanates, followed by S-alkylation of the thiourea compounds. Unexpectedly, the two classes of derivatives show a similar in vitro antibacterial activity against Gram-positive bacteria. Thiourea compounds, due to the lack of a positively charged N-terminus group, have a 10-fold lower binding constant to Ac-D-Ala-D-Ala, a bacterial cell-wall model, than the parent antibiotic and isothiouronium salt derivatives.

S-Aryl(tetramethyl)isothiouronium salts as possible antimicrobial agents--III.

A series of S-Aryl(tetramethyl)isothiouronium salts were prepared and evaluated in vitro for antimicrobial activity. Some compounds revealed interesting inhibiting action on Gram-positive bacteria which is noteworthy in view of the large number of strains antagonized and of the low MIC values. The possible influence of decomposition kinetics to the corresponding mercaptoderivatives was intestigated and compared with those of salts previously studied.