Synthesis, structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands

Intercalation of a Zn(II) complex containing ciprofloxacin drug between DNA base pairs

In this study, an attempt has been made to study the interaction of a Zn(II) complex containing an antibiotic drug, ciprofloxacin, with calf thymus DNA using spectroscopic methods. It was found that Zn(II) complex could bind with DNA via intercalation mode as evidenced by: hyperchromism in UV-Vis spectrum; these spectral characteristics suggest that the Zn(II) complex interacts with DNA most likely through a mode that involves a stacking interaction between the aromatic chromophore and the base pairs of DNA. DNA binding constant (K_b = 1.4 × 10⁴ M^-1) from spectrophotometric studies of the interaction of Zn(II) complex with DNA is comparable to those of some DNA intercalative polypyridyl Ru(II) complexes 1.0 -4.8 × 10⁴ M^-1. CD study showed stabilization of the right-handed B form of DNA in the presence of Zn(II) complex as observed for the classical intercalator methylene blue. Thermodynamic parameters (ΔH < 0 and ΔS < 0) indicated that hydrogen bond and Van der Waals play main roles in this binding prose. Competitive fluorimetric studies with methylene blue (MB) dye have shown that Zn(II) complex exhibits the ability of this complex to displace with DNA-MB, indicating that it binds to DNA in strong competition with MB for the intercalation.

Interaction of zinc(II) with the non-steroidal anti-inflammatory drug niflumic acid

The reaction of ZnCl2 with the non-steroidal anti-inflammatory drug niflumic acid (Hnif) resulted in the formation of complex [Zn(nif-O)2(MeOH)4], 1. When this reaction was performed in the presence of a N,N'-donor heterocyclic ligand such as 2,2'-bipyridine (bipy), 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) and 2,2'-dipyridylketone oxime (Hpko), the complexes [Zn(nif-O,O')(bipy)Cl], 2, [Zn(nif-O)(nif-O,O')2(bipyam)], 3, [Zn(nif-O,O')2(phen)], 4 and [Zn(nif-O)2(Hpko-N,N')2], 5 were formed, respectively. The complexes were characterized by physicochemical and spectroscopic techniques and X-ray crystallography (for complexes 1-3). The complexes can scavenge 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals, may inhibit soybean lipoxygenase and are more active compounds than free Hnif. The interaction of the complexes with serum albumins was monitored by fluorescence emission spectroscopy and the corresponding binding constants were calculated. The affinity of the complexes with calf-thymus DNA was investigated by UV-vis spectroscopy, viscosity measurements and fluorescence emission spectroscopy for the competitive studies of the complexes with ethidium bromide revealing their interaction probably via intercalation.

Ex vivo trypanocidal activity of 1-(2-hydroxybenzylidene)thiosemicarbazide against Trypanosoma equiperdum

Trypanosoma equiperdum is the causative agent of dourine, a venereal disease in horses and donkeys. This parasite has a widely distribution, is found in Africa, Asia, Southern and Eastern Europe, Russia, Mexico and Venezuela. The T. equiperdum is morphologically indistinguishable to other Trypanozoon species, however differs from other mammalian trypanosomes due to the fact that it is primarily a tissue parasite, generating cutaneous plaques, swelling of genitalia and neurological signs. The aim of this study was to evaluate the trypanocidal effectiveness of a set of derivatives of thiosemicarbazones on a T. equiperdum ex vivo culture. All compounds appeared to have trypanocidal activity, however one of them shown better solubility and a dose-dependent effect. The median inhibitory concentration (IC₅₀) was 1.2μM. The selected compound exhibits a greater inhibitory activity than diminazene aceturate, a common drug for animal trypanosomosis treatment.

Synthesis, characterization and crystal structures of two pentagonal-bipyramidal Fe(III) complexes with dihydrazone of 2,6-diacetylpyridine and Girard's T reagent. Anticancer properties of various metal complexes of the same ligand

In this work synthesis, characterization and crystal structures of two isothiocyanato Fe(III) complexes with 2,2'-[2,6-pyridinediylbis(ethylidyne-1-hydrazinyl-2-ylidene)]bis[N,N,N-trimethyl-2-oxoethanaminium] dichloride (H₂LCl₂) ligand, with composition [FeL(NCS)₂]SCN·2H₂O and [FeL(NCS)₂]₂[Fe(H₂O)(NCS)₅]·4H₂O, has been reported. Both iron(III) complexes possess the same pentagonal-bipyramidal complex cation, while the nature of their anions depends on mole ratio of NH₄SCN and FeCl₃·6H₂O used in reaction. Cytotoxic activity of new Fe(III) complexes, as well as of previously synthesized isothiocyanato Co(II), Ni(II), Mn(II), Zn(II) and Cd(II) complexes with the same ligand, was tested against five human cancer cell lines (HeLa, MDA-MB-453, K562, LS174 and A549) and normal cell line MRC-5. The best activity was observed in the case of Fe(III), Co(II) and Cd(II) complexes. The investigation of potential of these complexes to induce HeLa and K562 cell cycle perturbations was also evaluated. Mechanism of cell death mode was elucidated on the basis of morphological changes of HeLa cells as well as identification of target caspases. It was established that DNA damage could be responsible for the activity of Fe(III) and Co(II) complexes.

SYNOPSIS

Pentagonal-bipyramidal Fe(III) complexes with dihydrazone of 2,6-diacetylpyridine and Girard's T reagent have been synthesized and characterized. Cytotoxic activity of Fe(III) complexes and Co(II), Ni(II), Mn(II), Zn(II) and Cd(II) complexes with the same ligand was tested. The best activity was observed in the case of Fe(III), Co(II) and Cd(II) complexes.

Thiosemicarbazones and Phthalyl-Thiazoles compounds exert antiviral activity against yellow fever virus and Saint Louis encephalitis virus

Arboviruses, arthropod-borneviruses, are frequency associated to human outbreak and represent a serious health problem. The genus Flavivirus, such as Yellow Fever Virus (YFV) and Saint Louis Encephalitis Virus (SLEV), are important pathogens with high morbidity and mortality worldwide. In Brazil, YFV is maintained in sylvatic cycle, but many cases are notified annually, despite the efficiency of vaccine. SLEV causes an acute encephalitis and is widely distributed in the Americas. There is no specific antiviral drugs for these viruses, only supporting treatment that can alleviate symptoms and prevent complications. Here, we evaluated the potential anti-YFV and SLEV activity of a series of thiosemicarbazones and phthalyl-thiazoles. Plaque reduction assay, flow cytometry, immunofluorescence and cellular viability were used to test the compounds in vitro. Treated cells showed efficient inhibition of the viral replication at concentrations that presented minimal toxicity to cells. The assays showed that phthalyl-thiazole and phenoxymethyl-thiosemicarbazone reduced 60% of YFV replication and 75% of SLEV replication.

Three novel transition metal complexes of 6-methyl-2-oxo-quinoline-3-carbaldehyde thiosemicarbazone: synthesis, crystal structure, cytotoxicity, and mechanism of action

Complex 1 was more selective for MGC80-3 tumor cells versus normal cells (HL-7702). Importantly, 1 triggered MGC80-3 cells apoptosis via a mitochondrial dysfunction pathway.

Zinc complexes of flufenamic acid: Characterization and biological evaluation

The reaction of ZnCl2 with the non-steroidal anti-inflammatory drug flufenamic acid (Hfluf) led to the formation of complex [Zn(fluf-O)2(MeOH)4], 1. When the reaction takes places in the presence of a N,N'-donor heterocyclic ligand such as 2.2'-bipyridylamine (bipyam), 2.2'-bipyridine (bipy), 1.10-phenanthroline (phen) and 2.2'-dipyridylketone oxime (Hpko), the complexes [Zn(fluf)2(bipyam)], 2, [Zn(fluf)2(bipy)], 3, [Zn(fluf)(phen)2(H2O)](fluf)·0.2MeOH, 4·0.2MeOH and [Zn(fluf)2(Hpko)2], 5 were isolated, respectively. The complexes were characterized by physicochemical and spectroscopic techniques and the crystal structures of complexes 2 and 4 were determined by X-ray crystallography. The ability of the complexes to scavenge 1.1-diphenyl-picrylhydrazyl, 2.2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals and to inhibit soybean lipoxygenase was evaluated; the complexes were more active than free Hfluf. The interaction of the complexes with serum albumins was investigated by fluorescence emission spectroscopy and the corresponding binding constants were calculated. UV-vis spectroscopy, viscosity measurements and fluorescence emission spectroscopy for the competitive studies of the complexes with ethidium bromide were the techniques employed to monitor the interaction of the complexes with calf-thymus DNA and revealed intercalation as the most possible mode of binding.

Zinc(II)-Thiosemicarbazone Complexes Are Localized to the Lysosomal Compartment Where They Transmetallate with Copper Ions to Induce Cytotoxicity

As the di-2-pyridylketone thiosemicarbazone (DpT) and 2-acetylpyridine thiosemicarbazone (ApT) series show potent antitumor activity in vitro and in vivo, we synthesized their fluorescent zinc(II) complexes to assess their intracellular distribution. The Zn(II) complexes generally showed significantly greater cytotoxicity than the thiosemicarbazones alone in several tumor cell-types. Notably, specific structure-activity relationships demonstrated the importance of the di-2-pyridyl pharmacophore in their activity. Confocal fluorescence imaging and live cell microscopy showed that the Zn(II) complex of our lead compound, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which is scheduled to enter clinical trials, was localized to lysosomes. Under lysosomal conditions, the Zn(II) complexes were shown to transmetallate with copper ions, leading to redox-active copper complexes that induced lysosomal membrane permeabilization (LMP) and cytotoxicity. This is the first study to demonstrate direct lysosomal targeting of our novel Zn(II)-thiosemicarbazone complexes that mediate their activity via transmetalation with copper ions and LMP.

Syntheses and structures of discrete copper(II) and cadmium(II) supramolecular complexes based on 1,4-diacylthiosemicarbazone ligands

Thiosemicarbazides and their metal complexes have attracted considerable interest because of their biological activities and their flexibility, which allows the ligands to bend and rotate freely to accommodate the coordination geometries of various metal centres. Discrete copper(II) and cadmium(II) complexes have been prepared by crystallization of N-[2-(2-hydroxybenzoyl)hydrazinecarbonothioyl]propanamide (H3L) with Cu(CH3COO)2 or Cd(NO3)2 in a dimethylformamide/methanol mixed-solvent system at room temperature, affording the complexes di-μ-acetato-bis{μ4-1-[(2-oxidophenyl)carbonyl]-2-(propanamidomethanethioyl)hydrazine-1,2-diido}tetracopper(II) dimethylformamide disolvate, [Cu4(C11H10N3O3S)2(C2H3O2)2]·2C3H7NO, (I), and bis{μ2-[(2-hydroxyphenyl)formamido](propanamidomethanethioyl)azanido}bis[(4,4'-bipyridine)nitratocadmium(II)] dihydrate, [Cd2(C11H12N3O3S)2(NO3)2(C10H8N2)2]·2H2O, (II). Complex (I) consists of four Cu(II) cations, two μ4-bridging trianionic ligands and two μ2-bridging acetate ligands, while complex (II) is composed of two Cd(II) cations, two μ2-bridging monoanionic ligands, two nitrate ligands and two 4,4'-bipyridine ligands. These discrete complexes are connected by hydrogen bonds and van der Waals interactions to form a three-dimensional supramolecular architecture. Compared with (I), the phenolic hydroxy group and hydrazide N atom of the thiosemicarbazide ligand of (II) are not involved in coordination and lead to a binuclear Cd(II) complex. This different coordination mode may be attributed to the larger ionic radius of the Cd(II) ion compared with the Cu(II) ion.

Synthesis of 5-acetyl-2-arylamino-4-methylthiazole Thiosemicarbazones under Microwave Irradiation and their in Vitro Anticancer Activity

A series of 21 new tri- and tetra-cyclic thiosemicarbazone derivatives were prepared via the condensation of morpholine, piperazine or N-(4-methoxyphenyl)piperazine with seven methyl hydrazine-carbodithioate derivatives of 5-acetyl-2-arylamino-4-methylthiazoles under microwave irradiation. All compounds were tested for their cytotoxic activity in vitro against human gastric, lung and breast cancer cell lines. The results showed that some of the compounds displayed moderate anticancer activity. The most potent compound, a morpholino-substituted analogue, exhibited significant activity against human breast cancer cells.

Synthesis, spectroscopy, structures and antimicrobial activity of mixed-ligand zinc(ii) complexes of 5-nitro-salicylaldehyde thiosemicarbazones

Zinc(ii)-thiosemicarbazone complexes have high antimicrobial activity against MRSA,S. aureus,K. pneumoniae,Sh. flexneri,S. typhimuriumandC. albicans.

Experimental and theoretical spectroscopic studies, HOMO-LUMO, NBO analyses and thione-thiol tautomerism of a new hybrid of 1,3,4-oxadiazole-thione with quinazolin-4-one

The hybrid 3-(4-chlorophenyl)-2-[(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)methylthio]quinazolin-4(3H)-one has been synthesized and characterized using elemental analysis, FTIR and NMR spectroscopy. The thione-thiol tautomeric equilibria has been studied using both DFT/B3LYP and HF methods at different basis sets. The results of calculations showed predominance of the thione form. The molecular structure and vibrational spectra of the stable tautomer are predicted using the same level of theory. The complete assignments of the vibrational modes were performed on the basis of potential energy distribution (PED). The 6-311++G(d,p) gave the best results compared to the experimental data. The chemical shift values of the two tautomers are calculated using GIAO method. The NH proton of the thione tautomer have chemical shift value closer to the experimental data compared to the SH proton of the thiol one. The electronic transitions are predicted using the TD-DFT calculations at B3LYP/6-311++G(d,p) level of theory. The calculated polarizability and first hyperpolarizability showed that the studied compound has better NLO properties than urea. The molecular electrostatic potential (MEP) analysis reveals the sites for electrophilic and nucleophilic attack in the molecule. NBO analysis is carried out to investigate the stabilization energy of various intramolecular charge transfer interactions within the studied molecule.

Molecular mechanisms of apoptosis and cell selectivity of zinc dithiocarbamates functionalized with hydroxyethyl substituents

In the solid state each of three binuclear zinc dithiocarbamates bearing hydroxyethyl groups, {Zn[S2CN(R)CH2CH2OH]2}2 for R = iPr (1), CH2CH2OH (2), and Me (3), and an all alkyl species, [Zn(S2CNEt2)2]2 (4), features a centrosymmetric {ZnSCS}2 core with a step topology; both 1 and 3 were isolated as monohydrates. All compounds were broadly cytotoxic, specifically against human cancer cell lines compared with normal cells, with greater potency than cisplatin. Notably, some selectivity were indicated with 2 being the most potent against human ovarian carcinoma cells (cisA2780), and 4 being more cytotoxic toward multidrug resistant human breast carcinoma cells (MCF-7R), human colon adenocarcinoma cells (HT-29), and human lung adenocarcinoma epithelial cells (A549). Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis in HT-29 cells is demonstrated via both extrinsic and intrinsic pathways. Compounds 2-4 activate the p53 gene while 1 activates both p53 and p73. Cell cycle arrest at the S and G2/M phases correlates with inhibition of HT-29 cell growth. Cell invasion is also inhibited by 1-4 which is correlated with down-regulation of NF-κB.

Thiosemicarbazone p-Substituted Acetophenone Derivatives Promote the Loss of Mitochondrial Δψ, GSH Depletion, and Death in K562 Cells

A series of thiosemicarbazone (TSC) p-substituted acetophenone derivatives were synthesized and chemically characterized. The p-substituents appended to the phenyl group of the TSC structures were hydrogen, fluor, chlorine, methyl, and nitro, producing compounds named TSC-H, TSC-F, TSC-Cl, TSC-Me, and TSC-NO₂, respectively. The TSC compounds were evaluated for their capacity to induce mitochondrial permeability, to deplete mitochondrial thiol content, and to promote cell death in the K562 cell lineage using flow cytometry and fluorescence microscopy. TSC-H, TSC-F, and TSC-Cl exhibited a bell-shaped dose-response curve for the induction of apoptosis in K562 cells due to the change from apoptosis to necrosis as the principal mechanism of cell death at the highest tested doses. TSC-Me and TSC-NO₂ exhibited a typical dose-response profile, with a half maximal effective concentration of approximately 10 µM for cell death. Cell death was also evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which revealed lower toxicity of these compounds for peripheral blood mononuclear cells than for K562 cells. The possible mechanisms leading to cell death are discussed based on the observed effects of the new TSC compounds on the cellular thiol content and on mitochondrial bioenergetics.

A mononuclear zinc(II) complex with piroxicam: crystal structure, DNA- and BSA-binding studies; in vitro cell cytotoxicity and molecular modeling of oxicam complexes

A new mononuclear Zn(II) complex, trans-[Zn(Pir)2(DMSO)2], where Pir(-) is 4-hydroxy-2-methyl-N-2-pyridyl-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide (piroxicam), has been synthesized and characterized. The crystal structure of the complex was obtained by the single crystal X-ray diffraction technique. The interaction of the complex with DNA and BSA was investigated. The complex interacts with FS-DNA by two binding modes, viz., electrostatic and groove binding (major and minor). The microenvironment and the secondary structure of BSA are changed in the presence of the complex. The anticancer effects of the seven complexes of oxicam family were also determined on the human K562 cell lines and the results showed reasonable cytotoxicities. The interactions of the oxicam complexes with BSA and DNA were modeled by molecular docking and molecular dynamic simulation methods.

Crystal structures of crotonaldehyde semicarbazone and crotonaldehyde thiosemicarbazone from X-ray powder diffraction data

Crotonaldehyde semicarbazone {systematic name: (E)-2-[(E)-but-2-en-1-yl-idene]hydrazinecarboxamide}, C5H9N3O, (I), and crotonaldehyde thio-semi-carba-zone {systematic name: (E)-2-[(E)-but-2-en-1-yldene]hydra-zinecarbo--thio-amide}, C5H9N3S, (II), show the same E conformation around the imine C=N bond. Compounds (I) and (II) were obtained by the condensation of crotonaldehyde with semicarbazide hydro-chloride and thio-semicarbazide, respectively. Each mol-ecule has an intra-molecular N-H⋯N hydrogen bond, which generates an S(5) ring. In (I), the crotonaldehyde fragment is twisted by 2.59 (5)° from the semicarbazide mean plane, while in (II) the corresponding angle (with the thio-semicarbazide mean plane) is 9.12 (5)°. The crystal packing is different in the two compounds: in (I) inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into layers parallel to the bc plane, while weak inter-molecular N-H⋯S hydrogen bonds in (II) link the mol-ecules into chains propagating in [110].

A value-added use of volatile turpentine: antifungal activity and QSAR study of β-pinene derivatives against three agricultural fungi

22 derivatives from β-pinene were synthesized and their fungicidal activities against three pathogenic fungi were investigated. Studies showed that the introduction of an electron withdrawing group was favorable towards the fungicidal activity.

Synthesis and structures of 5-nitro-salicylaldehyde thiosemicarb-azonates of copper(ii): molecular spectroscopy, ESI-mass studies, antimicrobial activity and cytotoxicity

Salicylaldehyde thiosemicarbazonates of copper(ii) have shown significant growth inhibitory activity againstS. aureus, MRSA,K. pneumonia,S. flexneri,P. aeruginosaandC. albicansand are bactericidal in nature with low cytotoxicity.

DNA- and BSA-binding studies and anticancer activity against human breast cancer cells (MCF-7) of the zinc(II) complex coordinated by 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine

Binding studies of a mononuclear zinc(II) complex, [Zn(dppt)2Cl2] (dppt is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine), with DNA and bovine serum albumin (BSA) have been investigated under physiological conditions. The binding properties of the complex with fish sperm DNA (FS-DNA) have been investigated by UV-Vis absorption, thermal denaturation, competitive DNA-binding studies with ethidium bromide (EB) by fluorescence, and gel electrophoresis techniques. The competitive study with (EB) shows that the complex can displace EB from the DNA-EB system and compete for the DNA-binding sites with EB, which is usually characteristic of the intercalative interaction of compounds with DNA. The value of the fluorescence quenching constant (Ksv) was obtained as 3.1×10(4)M(-1), indicating that this complex shows a high quenching efficiency and a significant degree of binding to DNA. Moreover, the intercalative binding mode has also been verified by the results of UV-Vis absorption, thermal denaturation and gel electrophoresis. The value of Kb at room temperature was calculated to be 1.97×10(5)M(-1), indicating that the complex possesses strong tendency to bind with DNA. This value is very greater than to the values obtained for other zinc(II) complexes. The interaction of the complex with BSA has been studied by UV-Vis absorption, fluorescence and circular dichroism (CD) spectroscopic techniques. The results indicate that the complex has a quite strong ability to quench the fluorescence of BSA and the binding reaction is mainly a static quenching process. The quenching constants (KSV), the binding constants (Kb), the number of binding sites at different temperatures, the binding distance between BSA and the complex (r), and the thermodynamic parameters (ΔH(o), ΔS(o) and ΔG(o)) between BSA and the complex were calculated. The complex exhibits good binding propensity to BSA showing relatively high binding constant values. The positive ΔH(o) and ΔS(o) values indicate that the hydrophobic interaction is main force in the binding of the complex to BSA. Moreover, to evaluate the anticancer properties, the cytotoxicity of the complex has been tested against the human breast adenocarcinoma (MCF-7) cell lines using the MTT assay. The results indicate that the parent complex displays cytotoxicity against human breast cancer cell lines (MCF-7) with an IC50 value of 10.44μM. It is remarkable that the complex can introduce as a potential anticancer drug.

Design and synthesis of novel 5,6-disubstituted pyridine-2,3-dione-3-thiosemicarbazone derivatives as potential anticancer agents

A series of 5,6-disubstituted pyridine-2,3-dione-3-thiosemicarbazone derivatives(2a-2n) and 5,6-disubstituted pyridine-2,3-dione S-benzyl-3-thiosemicarbazones(3a-3g) were synthesized starting from 2,3-dihydroxypyridine via oxidation-Michael additions, condensations and nucleophilic substitutions. The structures of the compounds were established by IR, (1)H NMR, (13)C NMR, and HRMS. All newly synthesized compounds were screened for their anticancer activity against Breast cancer (MCF-7), Colon cancer (HCT-116) and hepatocellular cancer (BEL7402) cell lines. Bioassay results indicated that most of the prepared compounds exhibited cytotoxicity against various cancer cells in vitro. Some of the compounds exhibited promising antiproliferative activity, which were comparable to the positive control (5-fluorouracil). The structure-activity relationship was discussed.

Poly[[(μ2-4,4'-bipyridyl-κ(2) N:N')bis-{μ2-N-[2-(2-hy-droxy-benzo-yl)carbamo-thio-yl]acetamidato-κ(4) O,N,O':S}bis-(nitrato-κ(2) O,O')dicadmium] di-methyl-formamide tetra-solvate]

The asymmetric unit of the title complex, {[Cd₂(C₁₀H₁₀N₃O₃S)₂(C₁₀H₈N₂)(NO₃)₂]·4C₃H₇NO}_n, consists of one Cd^II cation, one N-[2-(2-hy­droxy­benzo­yl)carbamo­thio­yl]acetamidate ligand, half a 4,4′-bipyridyl ligand, one coordinating nitrate anion and two di­methyl­formamide solvent mol­ecules of crystallization. The bipyridine ligand is completed by inversion symmetry. The metal cation exhibits a distorted penta­gonal–bipyramidal coordination geometry provided by two O and one N atoms of the thio­semicarbazide ligand, two O atoms of the nitrate anion, one S atom of a neighbouring thio­semicarbazide ligand and one 4,4′-bi­pyridine N atom. The bridging role of the thio­semicarbazide ligand through the S atom leads to centrosymmetric binuclear units, which are further linked by 4,4′-bi­pyridine units, forming polymeric chains extending along the b-axis direction. An intra­molecular N—H⋯O hydrogen bond occurs. The crystal structure also features N—H⋯O and O—H⋯O hydrogen bonds, leading to the formation of a three-dimensional network.

Antioxidant capacity and DNA-interaction studies of zinc complexes with a non-steroidal anti-inflammatory drug, mefenamic acid

Zinc(II) complexes of a non-steroidal anti-inflammatory drug, mefenamic acid(=Hmef) in the absence or presence of the nitrogen donor heterocyclic ligands 2,2'-bipyridine(=bipy), 2,2'-bipyridylamine(=bipyam), 2,2'-dipyridylketone oxime(=Hpko) or 1,10-phenanthroline(=phen) have been synthesized and characterized. The crystal structures of [Zn(mef-O,O')2(bipy)], 2, [Zn(mef-O)2(Hpko-N,N')2]·EtOH, 4 and [Zn(mef-O)(mef-O,O')(phen)(H2O)], 5, have been determined by X-ray crystallography showing distinct binding modes of mefenamato carboxylato group, bidentate in 2, monodentate in 4 or both in 5. Interaction studies of the complexes with calf-thymus DNA (CT DNA) have shown that complexes can bind to CT DNA with [Zn(mef-O)2(Hpko)2] exhibiting the highest binding constant to CT DNA (Kb = 1.93(±0.04) × 10(7) M(-1)). The complexes can bind to CT DNA via intercalation as concluded by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have shown that the complexes can displace the DNA-bound EB. The complexes exhibit good binding affinity to serum albumin proteins with [Zn(mef-O)2(H2O)4], 1 exhibiting the highest quenching ability (kq = 1.46 × 10(15) M(-1) s(-1) for human and 5.55 × 10(15) M(-1) s(-1) for bovine serum albumin). All compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase. The scavenging activity is low to moderate against 1,1-diphenyl-picrylhydrazyl (DPPH) radicals and high against hydroxyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+·)) radicals, with [Zn(mef-O)2(H2O)4], 1 (ABTS%, 0.1 mM: 94.75(±1.06)%; (·)OH%, 0.1mM: 96.69(±0.27)%; LOX: IC50 = 27.34(±0.90) μM) exhibiting the highest scavenging activity of the ABTS radical cation among the complexes. Additionally, the complexes exhibit higher scavenging and LOX inhibitory activity than free mefenamic acid (ABTS%, 0.1 mM: 66.32(±0.38)%; (·)OH%, 0.1 mM: 92.51(±0.44)%; LOX: IC50 = 48.52(±0.88) μM).

Development of new zinc dithiosemicarbazone complex for use as oral antidiabetic agent

The increasing prevalence of diabetes mellitus (DM) worldwide has underscored the urgency of developing an efficient therapeutic agent. Recently, Zn complexes have been attracting attention due to their antidiabetic activity. In this study, we designed and synthesized a new Zn complex, Zn-3,4-heptanedione-bis(N (4)-methylthiosemicarbazonato) (Zn-HTSM), characterized its physicochemical properties, and examined its antidiabetic activity in KK-A(y) type 2 DM model mice. It was demonstrated that Zn-HTSM has adequate lipophilicity for the cellular permeability, shows potent hypoglycemic activity, and improves glucose intolerance in KK-A(y) mice. We also analyzed the levels of serum adipokines after continuous oral administration of Zn-HTSM. The level of serum leptin of KK-A(y) mice is significantly reduced by the treatment of Zn-HTSM. Nevertheless, the levels of serum insulin and adiponectin were not improved. These data suggested that the Zn-HTSM acts on the leptin metabolism. Our present studies indicate that Zn-HTSM is a candidate oral antidiabetic agent for the treatment of type 2 DM.