Bahri Ülküseven

Synthesis, characterization and antidiabetic properties of N1-2,4-dihydroxybenzylidene-N4-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato-oxovanadium(IV)

A new oxovanadium(IV) chelate [VOL] (L: N(1)-2,4-dihydroxybenzylidene-N(4)-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato) was synthesized and characterized by elemental analysis, conductivity and magnetic measurements, UV-vis, IR, EPR spectroscopy and mass spectrometry. The biochemical and immunohistochemical effects of the administration of the vanadium complex (VOL) into the pancreas of normal and streptozotocin-induced diabetic rats were profoundly investigated. The animals were randomly divided into four groups. Group I: control (intact) animals. Group II: control animals administered with VOL. Group III: STZ-induced diabetic animals. Group IV: STZ-induced diabetic animals administered with VOL. VOL was given to some of the experimental animals by gavage at a dose of 0.2mM/kg every day for 12 days. Blood samples were collected from animals, on 0 and 1, 6 and 12 days after STZ injection. On day 12, the pancreatic tissues were taken from the animals. The tissue sections were labelled with streptavidin biotin peroxidase technique for insulin. In the diabetic group, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were increased. But, in the diabetic+VOL groups, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were reduced. In the diabetic group, a decrease in the pancreatic glutathione levels, glutathione peroxidase and superoxide dismutase activities and an increase in the pancreatic lipid peroxidation level and catalase activities were observed. The administration of VOL to the diabetic rats reversed this diabetic effect due to its insulinomimetic effects. According to the immunohistochemical and biochemical results obtained, it was concluded that VOL can regenerate B cells of the pancreas in experimental diabetes and has an antidiabetic and protective effects on the pancreas.

Antimicrobial Activity of a Series of Thiosemicarbazones and Their Zn II and Pd II Complexes

Thirty-four thiosemicarbazones andS-alkyl thiosemicarbazones, and some of their ZnII and PdII complexes were obtained and purified to investigate antimicrobial activity. MIC values of the compounds were determined by the disc diffusion method againstEscherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Staphylococcus aureus, S. epidermidis, andCandida albicans. The thiosemicarbazones show antibacterial and antifungal effects in free ligand and metal-complex form. Picolinaldehyde-S-methyl- and -S-benzylthiosemicarbazones did not affect the tested microorganisms but their ZnII complexes showed selective activity. The antimicrobial activity is relatively high in Me2SO, but the antimicrobial potential is changed in a certain range with Me2SO, HCONMe2, EtOH and CHCl3.

Oxovanadium(IV) complexes of bromo-and methoxy substituted N1,N4-diarylidene-S-methylthiosemicarbazones

Four new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations. The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis, conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g‖ < g⊥ < ge = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The EPR spectra recorded from solution forms almost have isotropic character.

Zn(II) and Pd(II) Complexes of Thiosemicarbazone‐S‐alkyl Esters Derived from 2/3‐Formylpyridine

Abstract Representative S‐methyl/ethyl‐4‐H/phenylthiosemicarbazones and their Zn(II) and Pd(II) complexes were synthesized. Characterization of the 1:1 complexes, [Zn(L)Cl2], [Pd(L)Cl2], and [Pd(L)Cl]Cl, was accomplished by means of elemental analyses, IR and 1H NMR spectra. The multidentate S‐alkyl thiosemicarbazones coordinate as mono‐, bi‐, or tridentate ligands depending on the types of the alkyl moiety and metal ion.

1,2-Bis-(2-benzimidazolyl)-1,2-ethanediol and 1,4-bis-(2-benzimidazolyl)-1,2,3,4-butanetetraol PdCl2 complexes

The 1,2-bis-(2-benzimidazolyl)-1,2-ethanediol (EH2) and 1,4-bis-(2-benzimidazolyl)-1,2,3,4-butanetetraol (TH4) ligands form 4-coordinate mono- and bi-metallic complexes with PdCl2, respectively. In Pd(EH2)Cl2 the ligand acts as a bidentate through two of the nitrogen atoms. On the other hand, in Pd2(TH4)Cl4 the ligand coordinates to two palladium atoms through both bis-benzimidazole nitrogen atoms and two oxygen atoms of the hydroxy groups, forming two different isomers. The complexes were characterised by analytical data, magnetic susceptibility, molar conductivity, and also by i.r., 1H- and 13C-n.m.r. spectra.

Antimicrobial activity of FeIII, CuII, AgI, ZnII and HgII complexes of 2-(2-hydroxy-5-bromo/nitro-phenyl)-1H- and 2-(2-hydroxyphenyl)-5-methyl/chloro/nitro-1H-benzimidazoles.

Antimicrobial activity of 2-(2-hydroxyphenyl)-5-R5-1H-benzimidazoles, 2-(2-hydroxy-5-R5′-phenyl)-1H-benzimidazoles and their FeIII, CuII, AgI, ZnII and HgII nitrate complexes was tested towardStaphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, andProteus mirabilis. Antifungal activity was tested againstCandida albicans. Benzimidazole benzene ring substituents increase the antimicrobial activity, phenol ring substituents decrease it. The ligands show an antibacterial effect against onlyS. aureus whereas AgI and HgII complexes of the ligands have a higher activity with respect to the other complexes to all the bacteria. On the other hand, FeIII complexes show a considerable activity againstS. aureus andS. epidermidis.

Synthesis and characterization of new dioxomolybdenum(VI) complexes derived from benzophenone-thiosemicarbazone (H2L). Crystal structure of [MoO2L(PrOH)]

Five mixed-ligand complexes of dioxomolybdenum(VI) [MoO2L(ROH)], where L is dianionic form of the 2-hydroxybenzophenone S-methyl-4-phenyl-thiosemicarbazone (H2L) and ROH are n-alcohols (C n H2n+1–OH; n = 1 − 5) were synthesized and characterized by elemental analysis, electronic, infrared and 1H-NMR spectroscopies. The ligand is coordinated to the cis- core through ONN, while the sixth coordination site is occupied by alcohol. The crystal structure of [MoO2L(PrOH] complex was determined by single crystal X-ray diffraction method. Effect of the 4-phenyl substituent on conjugation of chelate rings was discussed.

Synthesis and antioxidant activities of transition metal complexes based 3-hydroxysalicylaldehyde-S-methylthiosemicarbazone.

The nickel(II), iron(III), oxovanadium(IV) complexes of the 3-hydroxysalicylidene-S-methyl-thiosemicarbazone (L) were obtained from the 3-hydroxysalicyldehyde-S-methylthiosemicarbazone with the R1-substituted-salicylaldehyde (R1: H, 3-OH) in the presence of Ni(II), Fe(III), VO(IV) as template ion. The ligand and its complexes were characterized by elemental analysis, electronic, UV/Vis., (1)HNMR, EPR and IR studies. The free ligand and its metal complexes have been tested for in vitro antioxidant capacity by reduction of copper(II) neocuproine (Cu(II)-Nc) using the CUPRAC method. The ligand exhibited more potent in vitro antioxidant capacity than its complexes. The obtained trolox equivalent antioxidant capacity (TEAC) value of the iron(III) complex (TEACCUPRAC=3.27) was higher than those of other complexes. Furthermore, the antioxidant activity of the free ligand and its complexes were determined by in vitro methods measuring the scavenging activity of reactive oxygen species (ROS) including hydroxyl radical (OH), superoxide anion radical (O2(-)), and hydrogen peroxide (H2O2), showing that especially the V(IV) and Fe(III) complexes had significant scavenging activity for ROS.

Antimicrobial activity of some 2- and 3-pyridinyl-1H-benzimidazoles and their FeIII, CuII, ZnII, and AgI complexes

Abstract2-(2-Pyridinyl)-(LI), 2-(6-methyl-2-pyridinyl)-(LII), 2-(6-methyl-2-pyridinyl)-5-methyl-(LIII), 2-(3-pyridinyl)- (LIV), 2-(3-pyridinyl)-5-methyl-1H-benzimidazoles (LV) and their complexes with Fe(NO3)3, Cu(NO3)2, Zn(NO3)2, and AgNO3 were synthesized and antibacterial activity of the compounds was tested towardStaphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Proteus mirabilis and antifungal activity againstCandida albicans. The methyl groups ofLIII increase the antimicrobial activity. The AgI complexes have considerable activity toward the microorganisms. Some ZnII complexes show an antimicrobial effect againstS. aureus andS. flexneri, although the ligands themselves have no effect. CuII complexes have a considerable antibacterial effect toS. aureus andS. epidermidis.

Iron(III) and nickel(II) complexes as potential anticancer agents: synthesis, physicochemical and structural properties, cytotoxic activity and DNA interactions

Template reactions of 2-hydroxy-R-benzaldehyde-S-methylisothiosemicarbazones (R = 3-methoxy or 4-hydroxy) with the corresponding aldehydes in the presence of FeCl3 and NiCl2 yielded N1,N4-disalicylidene chelate complexes. The compounds were characterized by means of elemental and spectroscopic methods. The structure of complex 1 was determined by X-ray single crystal diffraction. Crystal data (Mo Kα; 296 K) are as follows: monoclinic space group P21/c, a = 12.9857(8) A, b = 7.8019(4) A, c = 19.1976(12) A, β = 101.655(5)°, Z = 4. Cytotoxic effects of the compounds were evaluated by the MTT assay in K562 leukemia, ECV304 endothelial and normal mononuclear cells, and DNA fragmentation analysis using the diphenylamine reaction was performed. The DNA binding capacity of thiosemicarbazones at IC50 and different concentrations was investigated. The DNA fragmentation percentage of compound treated cells was higher than that of non-treated control cells but was higher for compound 3 (84%) compared to the others. The interaction of compounds 1–4 and DNA was investigated voltammetrically by using nucleic acid modified electrodes after the double stranded fish sperm DNA (fsDNA), or poly(dA)·poly(dT), was immobilized onto the surface of pencil graphite electrodes (PGEs). Accordingly, the oxidation signals of DNA bases, guanine and adenine, were measured by using differential pulse voltammetry (DPV). The changes in the signals of guanine and adenine were evaluated before and after the interaction process. The results indicated that compound 3 was cytotoxic at very low concentrations in K562 leukemia cells unlike other cells and that could damage the DNA double stranded form, specifically the adenine base. Therefore, it may have a selective antileukemic effect and drug potential.