Heterocyclic substituted thiosemicarbazones and their Cu(II) complexes: Synthesis, characterization and studies of substituent effects on coordination and DNA binding

New Stable Gallium(III) and Indium(III) Complexes with Thiosemicarbazone Ligands: A Biological Evaluation

The aim of this work is to explore a new library of coordination compounds for medicinal applications. Gallium is known for its various applications in this field. Presently, indium is not particularly important in medicine, but it shares a lot of chemical traits with its above-mentioned lighter companion, gallium, and is also used in radio imaging. These metals are combined with thiosemicarbazones, ligating compounds increasingly known for their biological and pharmaceutical applications. In particular, the few ligands chosen to interact with these hard metal ions share the ideal affinity for a high charge density. Therefore, in this work we describe the synthesis and the characterization of the resulting coordination compounds. The yields of the reactions vary from a minimum of 21% to a maximum of 82%, using a fast and easy procedure. Nuclear Magnetic Resonance (NMR) and Infra Red (IR) spectroscopy, mass spectrometry, elemental analysis, and X-ray Diffraction (XRD) confirm the formation of stable compounds in all cases and a ligand-to-metal 2:1 stoichiometry with both cations. In addition, we further investigated their chemical and biological characteristics, via UV-visible titrations, stability tests, and cytotoxicity and antibiotic assays. The results confirm a strong stability in all explored conditions, which suggests that these compounds are more suitable for radio imaging applications rather than for antitumoral or antimicrobic ones.

Cytotoxic activity of copper(ii), nickel(ii) and platinum(ii) thiosemicarbazone derivatives: interaction with DNA and the H2A histone peptide

Metal complexes still represent promising pharmacological tools in the development of new anticancer drugs. Bis(citronellalthiosemicarbazonate)nickel(ii) is a metal compound extremely effective against leukemic and NCS cancer cell lines. Preliminary experiments performed with this compound and with its Cu(ii) and Pt(ii) analogues evidenced alterations, detectable by comet assay, in the DNA of treated U937 cells. In addition, [Cu(tcitr)2] and [Pt(tcitr)2] were also able to induce gene mutations and produce frameshift events. To gain further insights into the mechanism of action of these metal compounds, we carried out a multidisciplinary study to investigate whether their biological activity can be ascribed to the direct interaction with DNA or with chromatin. The DNA interaction was investigated by means of CD and UV-Vis spectroscopic techniques and by AFM, whereas the chromatin interaction was studied by analyzing the effects of the compounds on the structure of a peptide that mimicks the potential metal binding site in the "C-tail" region of histone H2A by means of NMR, CD, UV-Vis and MS. The intensities of the effects induced by the metal compounds on the peptide follow the order [Ni(tcitr)2] > [Pt(tcitr)2] ≫ [Cu(tcitr)2]. From the AFM data, a remarkable DNA compaction was observed in the presence of [Pt(tcitr)2], while [Ni(tcitr)2] causes the formation of large interlaced DNA aggregates.

Guedes da Silva MF, Marzano C. Synthesis, Characterization and Biological Activity of Novel Cu(II) Complexes of 6-Methyl-2-Oxo-1,2-Dihydroquinoline-3-Carbaldehyde-4n-Substituted Thiosemicarbazones

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

Selectivity of a thiosemicarbazonatocopper(ii) complex towards duplex RNA. Relevant noncovalent interactions both in solid state and solution

Thiosemicarbazones and their metal derivatives have long been screened as antitumor agents, and their interactions with DNA have been analysed. Herein, we describe the synthesis and characterization of compounds containing [CuL]⁺ entities (HL = pyridine-2-carbaldehyde thiosemicarbazone) and adenine, cytosine or 9-methylguanine, and some of their corresponding nucleotides. For the first time, crystal structures of adenine- and 9-methylguanine-containing thiosemicarbazone complexes are reported. To the best of our knowledge, the first study on the affinity thiosemicarbazone-RNA is also provided here. Experimental and computational studies have shown that [CuL(OH₂)]⁺ entities at low concentration intercalate into dsRNA poly(rA)·poly(rU) through strong hydrogen bonds involving uracil residues and π-π stacking interactions. In fact, noncovalent interactions are present both in the solid state and in solution. This behaviour diverges from that observed with DNA duplexes and creates an optimistic outlook in achieving selective binding to RNA for subsequent possible medical applications.

Synthesis of copper and zinc 2-(pyridin-2-yl)imidazo[1,2-a]pyridine complexes and their potential anticancer activity

A small library of novel copper and zinc imidazo[1,2-a]pyridine complexes have been synthesized. Their structures were confirmed by X-ray diffraction crystallography and a selection of these compounds was tested against five cancer cell lines originating from breast cancer (MCF-7 and MDA-MB-231), leukemia (K562 and HL-60) and colorectal cancer (HT-29). The imidazo[1,2-a]pyridines and their zinc complexes showed poor anticancer activity, while the copper complexes were active against the cancer cell lines with IC₅₀ values comparable to and lower than camptothecin. For example, copper 6-bromo-N-cyclohexyl-2-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-amine acetate 21 had an IC₅₀ value lower than 1 μM against the HT-29 cells. Fluorescence microscopy with acridine orange, Hoechst 33342 and ethidium bromide, used in a preliminary investigation to evaluate morphological changes showed that copper 6-bromo-N-cyclohexyl-2-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-amine acetate 21 caused both apoptosis, necrosis and paraptosis in the MCF-7 and HL-60 cells. A select group of copper N-cyclohexyl-2-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-amines (26, 27, 29 and 31) induced apoptosis, paraptosis and deformed nuclei in MCF-7 cells.

Synthesis and Characterization of Novel Cu(II), Pd(II) and Pt(II) Complexes with 8-Ethyl-2-hydroxytricyclo(7.3.1.0(2,7))tridecan-13-one-thiosemicarbazone: Antimicrobial and in Vitro Antiproliferative Activity

New Cu(II), Pd(II) and Pt(II) complexes, (Cu(L)(H₂O)₂(OAc)) (1), (Cu(HL)(H₂O)₂(SO₄)) (2), (Cu(L)(H₂O)₂(NO₃)) (3), (Cu(L)(H₂O)₂(ClO₄)) (4), (Cu(L)₂(H₂O)₂) (5), (Pd(L)(OAc))H₂O (6), and (Pt(L)₂) (7) were synthesized from 8-ethyl-2-hydroxytricyclo(7.3.1.0^2,7)tridecan-13-one thiosemicarbazone (HL). The ligand and its metal complexes were characterized by IR, ¹H-NMR, ¹³C-NMR, UV-Vis, FAB, EPR, mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The free ligand and the metal complexes have been tested for their antimicrobial activity against E. coli, S. enteritidis, S. aureus, E. faecalis, C. albicans and cytotoxicity against the NCI-H1573 lung adenocarcinoma, SKBR-3 human breast, MCF-7 human breast, A375 human melanoma and HL-60 human promyelocytic leukemia cell lines. Copper complex 2 exhibited the best antiproliferative activities against MCF-7 human breast cancer cells. A significant inhibition of malignant HL-60 cell growth was observed for copper complex 2, palladium complex 6 and platinum complex 7, with IC₅₀ values of 1.6 µM, 6.5 µM and 6.4 µM, respectively.

Structural diversity in aroylthiourea copper complexes – formation and biological evaluation of [Cu(i)(μ-S)SCl]2, cis-Cu(ii)S2O2, trans-Cu(ii)S2O2 and Cu(i)S3 cores

Four different copper complexes containing aroylthiourea ligands displayed good interaction with CT DNA and BSA and cytotoxicity.

Two chiral alkanolamine Schiff base Cu(ii) complexes as potential anticancer agents: synthesis, structure, DNA/protein interactions, and cytotoxic activity

Two novel chiral copper complexes have been synthesized and expressed DNA/protein binding strength and substantial cytotoxic activity.

Chiral manganese (IV) complexes derived from Schiff base ligands: Synthesis, characterization, in vitro cytotoxicity and DNA/BSA interaction

Two new couples of chiral manganese (IV) complexes with Schiff-base ligands, Λ-[Mn(R-L(1))2]·2(CH3OH) (Λ-1) and Δ-[Mn(S-L(1))2]·2(CH3OH) (Δ-1), Λ-[Mn(R-L(2))2]·(H2O)2 (Λ-2) and Δ-[Mn(S-L(2))2]·(H2O)2 (Δ-2), {H2L(1)=(R/S)-(±)-1-[(1-hydroxymethyl-propylimino)-methyl]-naphthalen-2-ol, H2L(2)=(R/S)-(±)-1-[(1-Hydroxymethyl-2-phenyl-ethylimino)-methyl]-naphthalen-2-ol} have been synthesized, and fully characterized by elemental analyses, UV-Vis spectrum, circular dichroism spectrum, FT-IR spectrum, mass spectrum, and single crystal X-ray diffraction (SXRD). The interaction of the four chiral Mn (IV) complexes with CT-DNA and BSA were also investigated by various spectroscopic techniques (UV-visible, fluorescence spectroscopic). The results show that the Δ-complexes exhibit more efficient CT-DNA interaction with respect to the Λ-complexes. All the complexes could quench the intrinsic fluorescence of BSA by a static quenching process. In addition, the vitro cytotoxicity of these complexes toward four kinds of cancerous cell lines (A549, HeLa, HL-60, and Caco-2) was assayed by the MTT method, which exhibited to be selectively active against certain cell lines.

Application of montmorillonite-Cu(II)ethylenediamine catalyst for the decolorization of Chromotrope 2R with H₂O₂ in aqueous solution

The kinetics of decolorization of Chromotrope 2R (C2R) was studied spectrophotometrically using the montmorilloniteK10-Cu(II)ethylenediamine composite (MMTK10-Cu(en)2) as catalyst and H2O2 as oxidant in aqueous solution. The catalyst was prepared and characterized by SEM, FTIR, XRD and TGA techniques. The dependence of reaction rate on H2O2 concentration was examined under UV irradiation in the presence and absence of the catalyst, and in the presence of the catalyst without the UV irradiation. In all these reaction systems, the rate increased up to a maximum value and then decreased. The rate increased with increasing the concentration of the dye reaching a maximum. Also, the rate of decolorization reaction showed a significant increase with increasing the amount of the catalyst and temperature. The addition of NaCl to the reaction medium has accelerated the rate effectively. A similar catalyst, MMTKSF-Cu(en)2, has also been employed and was found to be less efficient compared with MMTK10-Cu(en)2.

Antibacterial, antifungal and in vitro antileukaemia activity of metal complexes with thiosemicarbazones

1-phenyl-3-methyl-4-benzoyl-5-pyrazolone 4-ethyl-thiosemicarbazone (HL) and its copper(II), vanadium(V) and nickel(II) complexes: [Cu(L)(Cl)]·C₂H₅OH·(1), [Cu(L)₂]·H₂O (2), [Cu(L)(Br)]·H₂O·CH₃OH (3), [Cu(L)(NO₃)]·2C₂H₅OH (4), [VO₂(L)]·2H₂O (5), [Ni(L)₂]·H₂O (6), were synthesized and characterized. The ligand has been characterized by elemental analyses, IR, ¹H NMR and ¹³C NMR spectroscopy. The tridentate nature of the ligand is evident from the IR spectra. The copper(II), vanadium(V) and nickel(II) complexes have been characterized by different physico-chemical techniques such as molar conductivity, magnetic susceptibility measurements and electronic, infrared and electron paramagnetic resonance spectral studies. The structures of the ligand and its copper(II) (2, 4), and vanadium(V) (5) complexes have been determined by single-crystal X-ray diffraction. The composition of the coordination polyhedron of the central atom in 2, 4 and 5 is different. The tetrahedral coordination geometry of Cu was found in complex 2 while in complex 4, it is square planar, in complex 5 the coordination polyhedron of the central ion is distorted square pyramid. The in vitro antibacterial activity of the complexes against Escherichia coli, Salmonella abony, Staphylococcus aureus, Bacillus cereus and the antifungal activity against Candida albicans strains was higher for the metal complexes than for free ligand. The effect of the free ligand and its metal complexes on the proliferation of HL-60 cells was tested.

Synthesis, characterization and biological activity of 2-acetylpyridine-α naphthoxyacetylhydrazone and its metal complexes [corrected]

A new series of complexes of Ni(II), Co(II), Cu(II), Cd(II), Mn(II), Hg(II) and UO2(2+) derived from 2-acetylpyridine-α-naphthoxyacetylhydrazone (HA2PNA) have been prepared and characterized by elemental analyses, spectral (IR, UV-visible, ESR and (1)H NMR) as well as magnetic and thermal measurements. The data revealed that the ligand acts as neutral NO, NN and NNO or mono-negative NNO chelate. On the basis of electronic spectral and magnetic moment data, an octahedral geometry is suggested for Mn(II), Co(II), Ni(II) and UO2(2+) complexes and a square planar arrangement for Cu(II) complex. The bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated to confirm the geometry of the ligand and the investigated complexes. The kinetic parameters were determined for thermal degradation stages of some complexes using Coats-Redfern and Horowitz-Metzger methods. Also, the ligand and its complexes were screened against antibacterial, antioxidant using DPPH radical and antitumor activities using in vitro Ehrlich ascites assay.

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 of new chiral heterocyclic Schiff base modulated Cu(II)/Zn(II) complexes: their comparative binding studies with CT-DNA, mononucleotides and cleavage activity

New Schiff base ligand L derived from the condensation reaction of 2-amino-3-formylchromone with (R)-2-amino-2-phenylethanol was synthesized and characterized which involves combination element of ammine functionality and naturally occurring heterocyclic chromone, 4H-benzopyran-4-one. Subsequently, their complexes 1 and 2 with Cu(NO₃)₂ and Zn(NO₃)₂, respectively were prepared. The DNA binding studies of the ligand L and complexes 1 and 2 with CT-DNA as compared to classical anticancer drug cisplatin were carried out by employing different optical methods viz, UV-vis, fluorescence, circular dichroism and viscosity measurements. Furthermore, the absorption studies, ¹H and ³¹P with mononucleotides were also monitored to examine the base specific interactions of the transition metal complexes which revealed a higher propensity of copper(II) complex 1 for 5'-GMP while for zinc(II) complex 2 towards 5'-TMP involving groove binding mechanism of the complexes towards DNA. The complex 1 exhibits a remarkable DNA cleavage activity with pBR322 DNA in presence of different activators and cleavage reaction involves various oxygen species suggesting the involvement of active oxygen species for the DNA scission.

The interaction of taurine-salicylaldehyde Schiff base copper(II) complex with DNA and the determination of DNA using the complex as a fluorescence probe

The interaction of taurine-salicylaldehyde Schiff base copper(II) (Cu(TSSB)2(2+)) complex with DNA was explored by using UV-vis, fluorescence spectrophotometry, and voltammetry. In pH 7.4 Tris-HCl buffer solution, the binding constant of the Cu(TSSB)2(2+) complex interaction with DNA was 3.49 x 10(4) L mol(-1). Moreover, due to the fluorescence enhancing of Cu(TSSB)2(2+) complex in the presence of DNA, a method for determination of DNA with Cu(TSSB)2(2+) complex as a fluorescence probe was developed. The fluorescence spectra indicated that the maximum excitation and emission wavelength were 389 nm and 512 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range of 0.03-9.03 microg mL(-1) for calf thymus DNA (CT-DNA), 0.10-36 microg mL(-1) for yeast DNA and 0.01-10.01 microg mL(-1) for salmon DNA (SM-DNA), respectively. The corresponding detection limits are 7 ng mL(-1) for CT-DNA, 3 ng mL(-1) for yeast DNA and 3 ng mL(-1) for SM-DNA. Using this method, DNA in synthetic samples was determined with satisfactory results.

Synthesis, characterization antibacterial and antiproliferative activity of novel Cu(II) and Pd(II) complexes with 2-hydroxy-8-R-tricyclo[7.3.1.0.(2,7)]tridecane-13-one thiosemicarbazone

Synthesis and biological activity investigation of complex compounds of Cu(II) are challenging issues because of the metal is not a xenobiotic one and the activity of ligands could be modulated by complexation. Complex combinations of Cu(II) and Pd(II) with thiosemicarbazone derivatives of 2-hydroxy-8-R-tricyclo[7.3.1.0.(2,7)]tridecane-13-one (where R=C(3)H(7), C(4)H(3)O) were synthesized. The characterization of the ligands and the newly formed compounds was done by (1)H NMR, (13)C NMR, UV-vis, IR, ESR spectroscopy, elemental analysis, molar electric conductibility and thermal studies. Experiments performed to identify the structures proved that the ligands coordinate to metal ions in different ways - neutral bidentate or mononegative bidentate. Also, if copper(II) acetate, copper(II) nitrate, copper(II) chloride and copper(II) thiocyanate were used, the ligands coordinated in a mononegative bidentate fashion. If copper(II) sulfate was used, the ligands coordinated in a neutral bidentate fashion. The biological activity for the copper(II) synthesized compounds was assessed in terms of antibacterial or antiproliferative activity. The antibacterial activity of the complexes against Staphylococcus aureus var. Oxford 6538, Escherichia coli ATCC 10536, Klebsielle pneumoniae ATCC 100131 and Candida albicans ATCC 10231 strains was studied and compared with that of free ligands. The effect of complex compounds on the proliferation of HeLa cells was tested. For all tested complexes an antiproliferative activity was noted at concentrations higher than 1 microM, but lower than 10 microM. Therefore, complex compounds of copper(II) were synthesized, structurally characterized and tested for biological activity, proving both antibacterial and antiproliferative activity.

Biological assays and noncovalent interactions of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) drugs with [poly(dA-dT)](2), [poly(dG-dC)] (2), and calf thymus DNA

The interaction of the Cu(II) drugs CuL(NO(3)) and CuL'(NO(3)) (HL is pyridine-2-carbaldehyde thiosemicarbazone and HL' is pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, in water named [CuL](+) and [CuL'](+)) with [poly(dA-dT)](2), [poly(dG-dC)](2), and calf thymus (CT) DNA has been probed in aqueous solution at pH 6.0, I = 0.1 M, and T = 25 degrees C by absorbance, fluorescence, circular dichroism, and viscosity measurements. The results reveal that these drugs act as groove binders with [poly(dA-dT)](2), with a site size n = 6-7, whereas they act as external binders with [poly(dG-dC)](2) and/or CT-DNA, thus establishing overall electrostatic interaction with n = 1. The binding constants with [CuL'](+) were slightly larger than with [CuL](+). The title compounds display some cleavage activity in the presence of thiols, bringing about the rupture of the DNA strands by the reactive oxygen species formed by reoxidation of Cu(I) to Cu(II); this feature was not observed in the absence of thiols. Mutagenic assays performed both in the presence and in the absence of S9 mix, probed by the Ames test on TA 98, TA 100, and TA 102, were negative. Weak genotoxic activity was detected for [CuL](+) and [CuL'](+), with a significative dose-response effect for [CuL'](+), which was shown to be more cytotoxic in the Ames test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assays. Methylation of the terminal NH(2) group enhances the antiproliferative activity of the pyridine-2-carbaldehyde thiosemicarbazones.