Zinc complexes with cyclic derivatives of α-ketoglutaric acid thiosemicarbazone: Synthesis, X-ray structures and DNA interactions

Thiosemicarbazones as Potent Anticancer Agents and their Modes of Action

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Thiosemicarbazones (TSCs) are a class of Schiff bases usually obtained by the condensation of thiosemicarbazide with a suitable aldehyde or ketone. TSCs have been the focus of chemists and biologists due to their wide range of pharmacological effects. One of the promising areas in which these excellent metal chelators are being developed is their use against cancer. TSCs have a wide clinical antitumor spectrum with efficacy in various tumor types such as leukemia, pancreatic cancer, breast cancer, non-small cell lung cancer, cervical cancer, prostate cancer and bladder cancer. To obtain better activity, different series of TSCs have been developed by modifying the heteroaromatic system in their molecules. These compounds possessed significant antineoplastic activity when the carbonyl attachment of the side chain was located at a position α to the ring nitrogen atom, whereas attachment of the side chain β or γ to the heterocyclic N atom resulted in inactive antitumor agents. In addition, replacement of the heterocyclic ring N with C also resulted in a biologically inactive compound suggesting that a conjugated N,N,S-tridentate donor set is essential for the biological activities of thiosemicarbazones. Several possible mechanisms have been implemented for the anticancer activity of thiosemicarbazones.

Antibacterial activity of metal complexes based on cinnamaldehyde thiosemicarbazone analogues

The development of microbial antibiotic resistance has become one of the biggest threats to global health and the search for new molecules active against resistant pathogenic strains is a challenge that must be tackled. In many cases nosocomial infections are caused by bacteria characterized by multi-drug resistance patterns and by their ability to produce biofilms. These properties lead to the persistence of pathogens in the hospital environment. This paper reports the synthesis and characterization of three thiosemicarbazone derivatives based on a compound containing the cinnamaldehyde natural scaffold but possessing different logPow values. These molecules are then used as ligands to prepare complexes of the Cu(II) and Zn(II) ions. All these compounds, ligands and complexes, were screened in vitro on stains of Escherichia coli and Klebsiella pneumoniae for their antibacterial activity. Despite their molecular similarity they revealed variegated behaviors. Only two of them present interesting antimicrobial properties and have also been studied to verify their stability in solution. The compound with the lowest partition coefficient is the most promising. The minimal bactericidal concentration on K. pneumoniae and E. coli of these substances are very interesting and demonstrate that the use of metalloantibiotics is a promising device to fight antibiotic resistance.

Calcium release induced by 2-pyridinecarboxaldehyde thiosemicarbazone and its copper complex contributes to tumor cell death

Thiosemicarbazones display significant antitumor activity and their copper complexes also exhibit enhanced biological activities in most situations, but the underlying mechanism is poorly understood. Therefore, investigation of the mechanism involved in the change upon chelation is required to extend our understanding of the effects of thiosemicarbazones. In the present study, the inhibitory effect of 2-pyridinecarboxaldehyde thiosemicarbazone (PCT) and its copper complex (PCT-Cu) on cell proliferation was investigated. The copper chelate exhibited a 3- to 10-fold increase in antitumor activity (with an IC50 <5 µM). The results showed that both PCT and PCT-Cu induced reactive oxygen species (ROS) generation in vitro and in vivo, caused cellular DNA fragmentation, depolarization of the mitochondrial membrane and cell cycle arrest. Western blotting showed that both PCT and PCT-Cu induced apoptosis. Upregulation of GRP78 in HepG2 cells following treatment with the agents indicated that endoplasmic reticulum (ER) stress occurred. Furthermore calcium release was revealed in this study, suggesting that PCT and PCT-Cu disturbed calcium homeostasis. It was noted that PCT-Cu sensitized thapsigargin‑stimulated calcium release from the ER, which was correlated with the ROS level they induced, implying that the antitumor activity of PCT and PCT-Cu partly stemmed from calcium mobilization, a situation that was reported in few studies. Our findings may significantly contribute to the understanding of the anti‑proliferative effect of the derivatives of thiosemicarbazones along with their antitumor mechanism.

cis-Dioxomolybdenum(VI) complexes of a new ONN chelating thiosemicarbazidato ligand; synthesis, characterization, crystal, molecular structures and antioxidant activities

5-Chloro-4-methyl-2-hydroxybenzophenone S-propyl-4-phenyl-thiosemicarbazone (H2L) and its cis-dioxomolybdenum(VI) complexes, in the general formula [MoO2(L)R-OH)] (R: methyl, 1; ethyl, 2; n-propyl, 3; n-butyl, 4; n-pentyl, 5), were synthesized and characterized by micro analysis, electronic, infrared and (1)H and (13)C NMR spectra. The crystal structures of complexes, 1 and 3, have been solved by direct methods (SIR92) and refined to the residual indexes R1=0.098 and R1=0.052 respectively. Complexes 1 and 3 are crystallized in the triclinic space group P-1 with Z=2. The crystal study of complex 1 showed the first example of intermolecular hydrogen bond for this type of molybdenum-thiosemicarbazone complexes. The hydrogen bond is between the hydroxyl proton of attached alcohol and an oxo oxygen (in MoO2(2+) unit) of another complex molecule, and its bond distance (1.767(1)Å) is shorter than from the σ-coordination bonds in complex 1. Antioxidant activities of the compounds were determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Ligand showed 23.61% DPPH radical scavenging activity at 250 mg/L concentration. Cupric Reducing Antioxidant Capacity (CUPRAC) was also evaluated and trolox-equivalent antioxidant capacity (TEAC) values were found for ligand, 1 and 3 as 0.51, 0.33 and 0.30 respectively.

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

The iron complex 3 was cytotoxic at low concentrations in K562 cells and could damage the DNA, specifically the adenine base.

Bis-amide transition metal complexes: isomerism and DNA interaction study

A quatridentate bis-amide ligand, N,N'-propylenebis(salicylamide) H2pbs, and its transition metal complexes [M(pbs)(H2O)2], where M=Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized and characterized by elemental analysis, UV-Vis, IR, NMR, Mass, EPR, molar conductivity, magnetic moment values and thermal analysis. The NMR spectrum of ligand evidences the E/Z isomerism. All the evidences reveal that the metal ions adopt octahedral geometry with metal:ligand:solvent ratio 1:1:2. The conductivity measurements exhibit that the complexes are non-electrolytes. DNA binding properties of these complexes have been explored by UV-Vis and cyclic voltammetry. The results indicate that these complexes are good intercalators.

Synthesis, characterization and DNA-binding properties of four Zn(II) complexes with bis(pyrrol-2-yl-methyleneamine) ligands

A novel series of bis(pyrrol-2-yl-methyleneamine) ligands H2L(n) (n = 1-4) were synthesized via condensation of diamines with two equivalents of 2-formyl-pyrrole (2). Their Zn(II) complexes were characterized by elemental analyses, mass spectra and IR spectra. The crystal structures of [ZnL(1)]2 and [ZnL(4)]2 obtained from ethanol solution was determined by X-ray diffraction analysis, each of them possesses a double-stranded helical geometry. In addition, the DNA-binding properties of the compounds have been fully investigated by absorption, fluorescence and viscosity measurements.

Metal complexes of retinoid derivatives with antiproliferative activity: synthesis, characterization and DNA interaction studies

9-cis-Retinal thiosemicarbazone and its Co(III), Ni(II) and Cu(II) complexes are synthesized and characterized. Central Co(III) atom is in an octahedral environment while Ni(II) and Cu(II) atoms are in a square planar environment. DNA binding constants and spectroscopic data show an intercalative behavior for the nickel complex; an external binding mode is envisaged for the ligand and its copper complex. No DNA interaction can be hypothesized for the cobalt complex. The free ligand and its Ni(II) and Cu(II) complexes have a good lipophilic degree for an efficient uptake by the cells. The metal complexes exhibit a proliferation inhibition action against cell line U937 at micromolar concentration. Cu(II) complex also induces apoptosis, while Ni(II) complex has a strong interaction with CT-DNA.

Two New Co(II) and Ni(II) Complexes with 3-(2-Pyridyl)pyrazole-Based Ligand: Synthesis, Crystal Structures, and Bioactivities

Two new Co(II) and Ni(II) complexes exhibiting DNA cytotoxic activities with 3-(2-pyridyl)pyrazole-based ligand, [Co(L)(3)](ClO(4))(2) (1) and [Ni(L)(3)](ClO(4))(2) (2) (L=1-[3-(2-pyridyl)-pyrazol-1-ylmethyl]-naphthalene) were synthesized and structurally characterized. Both 1 and 2 crystallized in the monoclinic system, space group P2(1)/c, for 1, a=12.8324(8), b=12.1205(8), c=33.27(2) A, beta=93.92(3) degrees and Z=4; for 2, a=12.8764(3), b=12.1015(3), c=33.2415(9) A, beta=93.998(1) degrees and Z=4. Among them, the Co(II) and Ni(II) ions were all coordinated by six N donors from three distinct L ligands. In addition, the cytotoxic activities of 1, 2 and L in vitro were evaluated against three different cancer cell lines HL-60 (human leukemia), BGC-823 (stomach cancer) and MDA-MB-435 (mammary cancer), respectively. The results showed that 1 exhibited significantly high cytotoxic activities against HL-60 and moderate activities against BGC-823 and MDA-MB-435. In order to further investigate the relationships between structures and DNA-binding behaviors of these complexes, the interactions of 1, 2 and L with calf thymus DNA (CT-DNA) were then subjected to thermal denaturation, viscosity measurements and spectrophotometric methods. The results indicated that 1 and 2 intercalated with DNA via L ligand. The intrinsic binding constants of 1, 2 and L with DNA were 1.6x10(4), 5.6x10(3) and 2.76x10(3) M(-1), respectively.

Synthesis, characterisation and cytotoxic properties of the N1,N4-diarylidene-S-methyl-thiosemicarbazone chelates with Fe(III) and Ni(II)

Reactions of 2-hydroxy-3-methoxy, 2-hydroxy-4-methoxy-benzaldehyde with 3- and 4-methoxy-substituted salicylaldehyde S-methyl-thiosemicarbazones in the presence of FeCl(3) and NiCl(2) resulted in the corresponding methoxy-substituted N(1),N(4)-diarylidene-S-methyl-thiosemicarbazone chelates. Characterisation of the compounds in the [Fe(L)Cl] and [Ni(L)] general formula was accomplished by means of elemental analysis, conductivity and magnetic measurements, (1)H NMR, UV-vis, IR and mass spectroscopy. Cytotoxicity and proliferation experiments using K562 chronic myeloid leukemia cell line and ECV 304 human endothelial cell line imply that the iron(III) chelates may have anti-leukemic effects with 3.5 microg/dl LD(50) dose.