Hasan Küçükbay

Synthesis, antibacterial and antifungal activities of electron-rich olefins derived benzimidazole compounds.

New benzimidazole derivatives were synthesised by electron-rich olefines (7, 8 and 9) with appropriate reagents. The compounds synthesised were identified by 1H NMR, 13C NMR, FT-IR spectroscopic techniques and elemental analysis. All compounds studied in this work were screened for their in vitro antimicrobial activities against the standard strains: Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and the yeasts Candida albicans and Candida tropicalis. Eleven of the compounds inhibited the growth of gram-positive bacteria (E. faecalis and S. aureus) at MIC values between 50 and 400 microg/ml. None of the compounds exhibit antimicrobial activity against Gram-negative bacteria (E. coli and P. Aeruginosa) at the concentrations studied (6.25-800 microg/ml). Nine of the tested compounds showed an antifungal activity with a range of the MICs between 50 and 400 microg/ml.

Serum Vitamin A and Beta-carotene Levels in Children with Recurrent Acute Respiratory Infections and Diarrhoea in Malatya

Deficiency of serum vitamin A is one of the widespread public health problem among pre-school children in developing countries. A limited number of studies have been done about this problem in Turkey and there is no similar work done in Malatya. Serum vitamin A and beta-carotene levels in 56 pre-school age children who had recurrent acute respiratory infections (ARI) or recurrent diarrhoea were determined by a UV/VIS spectrometer. The results obtained were compared with 35 healthy pre-school age children. Serum vitamin A (51.66 +/- 8.10 micrograms/dL) and beta-carotene (82.88 +/- 18.5 micrograms/dL) levels in children with ARIs were found significantly lower than the control group (58.14 +/- 9.07 micrograms/dL and 131.43 +/- 22.38 micrograms/dL, respectively) (P < 0.001). Serum vitamin A (47.21 +/- 8.27 micrograms/dL) and beta-carotene (81.63 +/- 15.41 micrograms/dL) levels in children with recurrent diarrhoea were also found significantly lower than the control group (58.14 +/- 9.07 micrograms/dL and 131.43 +/- 22.38 micrograms/dL, respectively) (P < 0.001).

Synthesis and antimalarial bioassay of quinine - peptide conjugates.

Amino acid and peptide conjugates of quinine were synthesized using microwave irradiation in 52–95% yields using benzotriazole methodology. The majority of these conjugates retain in vitro antimalarial activity with IC50 values below 100 nm, similar to quinine.

Antifungal activity of some bis-5-methylbenzimidazole compounds.

Twenty bis-5-methylbenzimidazole compounds were evaluated for theirin vitro antifungal activity againstCandida albicans andCandida tropicalis. Except for three all compounds exhibited an antifungal activity against these yeasts over a range of the minimum inhibitory concentration (MIC) between 25 and 800 mg/L.

Reactions of Electron-Rich Olefins with Proton-Active Compounds

Abstract: From the reaction of electron-rich olefins, bis(1,3-dimethylbenzimidazolidine-2-ylidene), I, or bis(3-methylbenzothiazolidine-2-ylidene), II with proton active compounds, such as dimethyl phosphite, diethyl phosphite, acetonitrile and benzaldehyde were obtained 2-substituted benzimidazole or benzothiazole derivatives. The compounds synthesized were identified by 1H, 13 C, 31P-NMR, mass, FT-IR spectroscopic techniques and micro analysis.

Synthesis, Characterization and Microwave-Promoted Catalytic Activity of Novel N-phenylbenzimidazolium Salts in Heck-Mizoroki and Suzuki-Miyaura Cross-Coupling Reactions under Mild Conditions

A number of novel benzimidazolium salts having aryl substituents such as N-phenyl, 4-chlorophenyl and various alkyl substituents were synthesized. Their microwave-assisted catalytic activities were evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions using a catalytic system consisting of Pd(OAc)2/K2CO3 in DMF/H2O under mild reaction conditions with consistent high yields, except those of 2-bromopyridine.

Evaluation of in vitro and in vivo toxic effects of newly synthesized benzimidazole-based organophosphorus compounds.

This paper reports the toxic properties of eight newly synthesized benzimidazole-based organophosphorus (OP) compounds in Xenopus laevis in both in vivo and in vitro conditions. For both experiments, a commercial solution of azinphos methyl (AzM, Gusathion M WP25) was used as a reference compound. The 24-h median lethal concentrations (LC₅₀) of all tested compounds were determined for 46th stage tadpoles in the range of 9.54-140.0 μM. For evaluation of the lethality of the compounds, the activity of the enzyme biomarkers acetylcholinesterase (AChE), carboxylesterase, glutathione S-transferase (GST), glutathione peroxidase, glutathione reductase, lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase were determined in vivo in X. laevis tadpoles exposed to three concentrations (LC₅₀, LC₅₀/2, and LC₅₀/4) of tested compounds. All exposure concentrations of AzM and seven of eight tested compounds caused CaE inhibition in in vivo conditions. Furthermore, the AChE inhibition capacity of tested compounds in commercial electric eel AChE and in X. laevis homogenates and also CaE inhibition capacity in only X. laevis homogenates were assayed for a 30-min in vitro exposure period. Eight OP compounds did not inhibit AChE activity more than 23 percent, but AzM exposure inhibited AChE activity by 26 percent for X. laevis homogenates and 97 percent for electric fish AChE in in vitro conditions. Also, CaE inhibition levels in X. laevis tadpole homogenates were 46 percent for AzM and between 8 percent and 33 percent for other compounds in in vitro conditions.

Preparation and characterization of trimethylsilyl-substituted benzimidazole metal complexes and structural characterization of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κ N 3]cobalt(II)

The ligands 1-trimethylsilylmethylbenzimidazole, 5-methyl-1-trimethylsilylmethylbenzimidazole, and 5-nitro-1-trimethylsilylmethylbenzimidazole and their Co(II) and Zn(II) complexes were synthesized and characterized by 1H-NMR, 13C-NMR, and elemental analyses. The crystal structure of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κN 3]cobalt(II) has been determined by single crystal X-ray diffraction.

Synthesis and carbonic anhydrase I, II, IV and XII inhibitory properties of N-protected amino acid - sulfonamide conjugates.

Abstract N-protected amino acids (Gly, Ala and Phe protected with Boc and Z groups) were reacted with sulfonamide derivatives, leading to the corresponding N-protected amino acid–sulfonamide conjugates. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA IV and hCA XII. Among them, hCA II, IV and XII are antiglaucoma drug targets, being involved in aqueous humor secretion within the eye. Low nanomolar inhibition was measured against all four isoforms with the 20 reported sulfonamides, but no selective inhibitory profiles, except for some CA XII-selective derivatives, were observed. hCA I, II and XII were generally better inhibited by sulfonamides incorporating longer scaffolds and Gly/Ala, whereas the best hCA IV inhibitors were homosulfanilamide derivatives, incorporating Phe moieties. The amino acid–sulfonamide conjugates show good water solubility and effective hCA II, IV and XII inhibition, and may be considered as interesting candidates for antiglaucoma studies.

Synthesis and carbonic anhydrase inhibitory properties of amino acid – coumarin/quinolinone conjugates incorporating glycine, alanine and phenylalanine moieties

Abstract N-Protected amino acids (Gly, Ala and Phe) were reacted with amino substituted coumarin and quinolinone derivatives, leading to the corresponding N-protected amino acid–coumarin/quinolinone conjugates. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against various human (h) isoforms, such as hCA I, hCA II, hCA IV and hCA XII. The quinolinone conjugates were inactive as enzyme inhibitors, whereas the coumarins were ineffective hCA I/II inhibitors (KIs > 50 μM) but were submicromolar hCA IV and XII inhibitors, with inhibition constants ranging between 92 nM and 1.19 μM for hCA IV, and between 0.11 and 0.79 μM for hCA XII. These coumarin derivatives, as many others reported earlier, thus show an interesting selective inhibitory profile for the membrane-bound over the cytosolic CA isoforms.