Synthesis,structure and cytotoxic activity of 2‐acetyl‐5‐trimethylsilylthiophene(furan) and their oximes

5‐Trimethylsilylderivatives of 2‐acetylthiophene and ‐furan have been regioselectively prepared by a one‐pot procedure from the corresponding 2‐acetylfuran or 2‐acetylthiophene using lithium N‐methylpiperazide (LNMP)–butyllithium–trimethylchlorosilane–water as the sequence of reagents. The ketones obtained were converted to the corresponding oximes. The structure of 2‐acetyl‐5‐trimethylsilylthiophene oxime (E‐isomer) has been studied by X‐ray diffraction. Formation of centrosymmetric dimers by means of H‐bonds has been observed. The intermolecular hydrogen bond O9? H…N8 length is 2.842(5) Å [H…N8 = 1.87 (6) Å, O9? H…N8 = 157(4)°]. Copyright © 2006 John Wiley & Sons, Ltd.     

Cytotoxicity of Metallic Complexes of Furan Oximes in Murine and Human Tissue Cultured Cell Lines

The copper complexes of furan oxime derivatives were found to be potent cytotoxic agents in both murine and human tissue cultured cell lines which were suspended as well as solid tumors. Mode of action studies in murine L1210 lymphoid leukemia cells showed that the compounds suppressed DNA, RNA and protein synthesis after 60 min at 100 μM. Inhibition of purine and pyrimidine de novo syntheses, as well as inhibition of ribonucleoside reductase and nucleoside kinase activities with DNA strand scission occurred. All of these effects of the drug probably added to its ability to cause cell death but most important was the inhibition of DNA topoisomerase II activity with IC₅₀ values lower than those afforded by VP-16, the standard, which should cause apoptosis. © 1997 John Wiley & Sons, Ltd.     

Multiple mechanisms for cytotoxicity induced by copper(II) complexes of 2‐acetylpyrazine‐N‐substituted thiosemicarbazones

The purpose of this study was to evaluate the mechanism by which 2‐acetylpyrazine‐⁴N‐substituted thiosemicarbazone copper II complexes mediate their cytotoxicity. These compounds were shown to be cytotoxic to a variety of human and rodent tumors in cell culture and are potent cytocidal agents as determined by dilute agar colony assays. They demonstrated the ability to inhibit several enzymes in vitro including DNA topoisomerase II activity. The data presented suggest that cytotoxicity may be mediated by the cumulative effect of several enzymes being inhibited by the agents. Copyright © 1999 John Wiley & Sons, Ltd.     

Cytotoxicity of syringin and 4-methoxycinnamyl alcohol isolated from Foeniculum vulgare on selected human cell lines

This study was carried out to determine the cytotoxic effect of seven plant extracts and the isolated compounds – syringin and 4-methoxycinnamyl alcohol – on cancerous and non-cancerous cells. The ethanol extract of Foeniculum vulgare was found to exhibit the most significant toxicity with an IC₅₀ value of 19.97 μg/mL on HeLa cells. Bioassay-guided fractionation led to the isolation of two compounds, syringin (1) and 4-methoxycinnamyl alcohol (2). Both compounds showed toxicity against MCF-7, HeLa and DU145 cancer cell line. The results showed that compound 2 showed high toxicity against all the cancer cell lines with IC₅₀ values of 14.24, 7.82 and 22.10 μg/mL, respectively. 4-Methoxycinnamyl alcohol also showed no apoptotic effect in cell cycle analysis after 48 h at a concentration of 10 μg/mL. However, DNA fragmentation study revealed that necrosis took place at a concentration of 10 μg/mL after 48 h exposure.     

Multi‐center nature of ethylene polymerization catalysts based on 2,6‐bis(imino)pyridyl complexes of iron and cobalt

2,6‐Bis(imino)pyridyl complexes of Fe and Co in combination with methylalumoxane form very active homogeneous catalytic systems for polymerization of ethylene. GPC analysis of the polymers prepared with the complexes indicates that the Co complexes produce single‐center catalysts whereas the Fe complexes produce catalysts with numerous types of active centers. Different centers in the latter catalyst systems respond differently to reaction conditions such as the reaction duration, the [MAO]:[Fe] ratio, the ethylene concentration, etc. The article examines the effects of reaction variables on the performance of both types of catalysts and proposes an explanation for the complex behavior of the catalysts derived from the Fe complexes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6159–6170, 2006     

Peroxidase activity of new mixed‐valence cobalt complexes with ligands derived from pyridoxal

New mixed‐valence cobalt complexes with ligands derived from pyridoxal were synthesized and characterized, and their application as mimetics of the peroxidase enzyme was investigated. Single‐crystal X‐ray diffraction was used to analyze all complex structures in the solid state and their electrochemical behavior was investigated. A reactivity pattern was observed in the complex synthesis regarding the cobalt compounds from which analogous zwitterionic derivatives were obtained. The importance of these compounds lies in understanding their behavior in an oxidizing environment and evaluating whether they can activate hydrogen peroxide to oxidize phenolic compounds. In nature, enzymes called peroxidases, which efficiently oxidize phenolic compounds, trigger many reactions involving the activation of hydrogen peroxide to oxidize organic substrates. However, these enzymes present several disadvantages, including denaturation and elevated costs. Therefore, these limitations can be overcome by expanding research into the study of synthetic catalysts for the oxidation of phenolic compounds using hydrogen peroxide, which is a highly relevant field of bioinorganic chemistry.     

Vinylic and ring‐opening metathesis polymerization of norbornene with bis(β‐ketoamine) cobalt complexes

Cobalt complexes 1 – 4 bearing N,O‐chelate ligands based on condensation products of 1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone with aniline, o‐methylaniline, α‐naphthylamine, and p‐nitroaniline, respectively, were synthesized, and the structures of 1 and 4 were characterized by single‐crystal X‐ray diffraction analyses. The bis(β‐ketoamine) cobalt complexes could act as moderately active catalyst precursors for norbornene polymerization with the activation of methylaluminoxane. This catalytic reaction proceeded mainly through a vinyl‐type polymerization mechanism. ¹H NMR and IR showed that in all cases, a small amount of double bonds raised from ring‐opening metathesis polymerization (ROMP) was present in the polymerization products. The variation of the polymerization conditions affected the ROMP unit ratio in the polynorbornenes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5535–5544, 2005     

Conformational changes of DNA molecules in interactions with bioactive compounds. II. DNA complexes with coordination compounds of cobalt and ruthenium

A comparative analysis is made of the character of conformational changes of the DNA molecule in its interaction with coordination compounds of cobalt and ruthenium with different ligand sets in the coordination sphere of the ion. It is shown that during complexation global conformational changes of DNA (e.g., the reduction of its volume) practically do not depend on the location and on the binding mode of the complex ion, but are primarily determined by its charge, whereas local conformational changes of the macromolecule are very sensitive to the type of the complex being formed, as indicated by the change of spectral properties of DNA. An assessment of sizes of the particles that are formed as a result of DNA condensation due to its binding with trivalent ions of cobalt and ruthenium was performed with the use of dynamic light scattering.     

Three new mixed‐ligand copper(II) complexes containing glycyl‐l‐valine and N,N‐aromatic heterocyclic compounds: Synthesis,characterization, DNA interaction,cytotoxicity and antimicrobial activity

Three novel copper(II) complexes, [Cu(Gly‐l ‐Val)(HPBM)(H₂O)]·ClO₄·H₂O ( 1 ), [Cu(Gly‐l ‐Val)(TBZ)(H₂O)]·ClO₄ ( 2 ) and [Cu(Gly‐l ‐Val)(PBO)(H₂O)]·ClO₄ ( 3 ) (Gly‐l ‐Val = glycyl‐l ‐valine anion, HPBM = 5‐methyl‐2‐(2′‐pyridyl)benzimidazole, TBZ = 2‐(4′‐thiazolyl)benzimidazole, PBO = 2‐(2′‐pyridyl)benzoxazole), have been prepared and characterized with elemental analyses, conductivity measurements as well as various spectroscopic techniques. The interactions of these copper complexes with calf thymus DNA were explored using UV–visible, fluorescence, circular dichroism, thermal denaturation, viscosity and docking analyses methods. The experimental results showed that all three complexes could bind to DNA via an intercalative mode. Moreover, the cytotoxic effects were evaluated using the MTT method, and the antimicrobial activity of these complexes was tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results showed that the activities are consistent with their DNA binding abilities, following the order of 1 > 2 > 3 .     

DFT and experimental determination of conformations of 2‐(ethoxycarbonylmethoxy)‐5‐(arylazo)benzaldehydes and their oximes

2‐(Ethoxycarbonylmethoxy)‐5‐(arylazo)benzaldehydes 1–4 and their oximes 5–8 were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopy. The favoured conformations of aldehydes 1–4 and oximes 5–8 were predicted theoretically. Selected geometrical parameters and charges were derived from optimized structures. IR, ¹H and ¹³C NMR data were also computed using Gaussian‐03 package and compared with the observed values. ¹⁵N and ¹⁷O chemical shifts were also determined theoretically. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,characterization and biological properties of mixed ligand complexes of cobalt(II/III) valproate with 2,9‐dimethyl‐1,10‐phenanthroline and 1,10‐phenanthroline

The synthesis of mononuclear cobalt(II/III) complexes with two different ligands (complex 2: [Co(valp)₂(2,9‐dmp)] and complex 3: [Co(valp)₂(H₂O)(1,10‐phen)]) was investigated and the characterization of both complexes was achieved using IR, UV–Vis, and single crystal X‐ray diffraction. Using single crystal X‐ray diffraction, the crystal structure of each of the complexes was determined. Additionally, the biological activity of these complexes was studied in five gram‐positive and four gram‐negative bacterial strains. Whereas in all gram‐negative bacteria tested, cobalt valproate complexes did not show any anti‐bacterial activity, both complexes had effects on gram positive bacteria. Complex 2 demonstrated good anti‐bacterial activity against all gram‐positive bacteria with inhibition zone diameter (IZD) ranging between 15–28 mm. Complex 3 exhibited low inhibition activity against all gram‐positive bacteria except E. faecalis with IZD ranging between 11.3–13.7 mm. Moreover, as an indication of its uses as industrial catalyst, the rate of bis(p‐nitrophenyl) phosphate (BNPP) hydrolysis when catalyzed by these complexes was measured at different temperatures, concentrations and pH. Complex 2 proved to be a better catalyst to induce the hydrolysis of BNPP.     

Synthesis,characterization and 1,3‐butadiene polymerization behaviors of cobalt complexes bearing 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands

A series of cobalt(II) complexes containing tridentate 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands (L) with the general formula [LCoCl₂] have been successfully synthesized and fully identified by IR spectroscopy, elemental analysis and mass spectroscopy. Cobalt complexes Co4–Co8 were further confirmed by X‐ray crystallographic analysis, and all the complexes adopted distorted trigonal pyramid geometries around the cobalt center. In combination with methylaluminoxane, the complexes exhibit high cis‐1,4‐selectivity for 1,3‐butadiene polymerization. The catalytic activities of the complexes mainly depend on the nature of the substituent and its position at the pyrazolyl ring of the ligand. Complexes having a bulkier substituent on the pyrazolyl ring of the ligand show lower catalytic activity and the incorporation of electron‐withdrawing substituent enhances the activity. Polymerization behaviors were almost not affected with varying [Al]/[Co] ratio, but both activity and the cis‐1,4 content decrease slightly as polymerization temperature increasing. Copyright © 2013 John Wiley & Sons, Ltd.     

Antioxidative vs cytotoxic activities of organotin complexes bearing 2,6‐di‐tert‐butylphenol moieties

Two series of organotin(IV) complexes with Sn–S bonds on the base of 2,6‐di‐tert‐butyl‐4‐mercaptophenol ( L ¹ SH ) of formulae Me₂Sn(L¹S)₂ ( 1 ); Et₂Sn(L¹S)₂ ( 2 ); Bu₂Sn(L¹S)₂ ( 3 ); Ph ₂ Sn(L¹S)₂ ( 4 ); (L¹)₂Sn(L¹S)₂ ( 5 ); Me₃Sn(L¹S) ( 6 ); Ph₃Sn(L¹S) ( 7 ) (L¹ = 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl), together with the new ones [Me₃SnCl(L²)] ( 8 ), [Me₂SnCl₂(L²)₂] ( 9 ) ( L ²  = 2‐(N‐3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)‐iminomethylphenol) were used to study their antioxidant and cytotoxic activity. Novel complexes 8 , 9 of Me_nSnCl_4 ? n (n = 3, 2) with Schiff base were synthesized and characterized by ¹H, ¹³C NMR, IR and elemental analysis. The crystal structures of compounds 8 and 9 were determined by X‐ray diffraction analysis. The distorted tetrahedral geometry around the Sn center in the monocrystals of 8 was revealed, the Schiff base is coordinated to the tin(IV) atom by electrostatic interaction and formation of short contact Sn–O 2.805 Å. In the case of complex 9 the distorted octahedron coordination of Sn atom is formed. The antioxidant activity of compounds as radical scavengers and reducing agents was proved spectrophotometrically in tests with stable radical DPPH, reduction of Cu²⁺ (CUPRAC method) and interaction with superoxide radical‐anion. Moreover, compounds have been screened for in vitro cytotoxicity on eight human cancer cell lines. A high activity against all cell lines with IC₅₀ values 60–160 nM was determined for the triphenyltin complex 7 , while the introduction of Schiff base decreased the cytotoxicity of the complexes. The influence on mitochondrial potential and mitochondrial permeability for the compounds 8 and 9 has been studied. It is shown that studied complexes depolarize the mitochondria but don't influence the calcium‐induced mitochondrial permeability transition.     

Thermal decomposition of nicotinate complexes of cobalt and nickel in dynamic nitrogen atmosphere

Thermal decomposition of cobalt and nickel nicotinate was studied by TG, DTG and DSC. The mechanism of decomposition has been established from TG and DSC data. The kinetic parameters namelyE, A together with ΔH were calculated from DSC curves using mechanistic and non-mechanistic integral equations.

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Zusammenfassung Mittels TG, DTG und DSC wurde die thermische Zersetzung von Cobaltund Nickelnikotinat untersucht. Der Zersetzungsmechanismus wurde anhand der TG-und DSC-Daten entwickelt. Die kinetischen ParameterE, A wurden zusammen mit ΔH anhand der DSC-Kurven mit Hilfe von mechanistischen und nichtmechanistischen Integrationsgleichungen berechnet.

     

Synthesis,characterization, biological studies and in vitro cytotoxicity on human cancer cell lines of titanium(IV) and tin(IV) derivatives with the α,α′‐dimercapto‐o‐xylene ligand

The reaction of α,α′‐dimercapto‐o‐xylene (H₂dmox) with different precursors such as SnMe₂Cl₂, [Ti(η⁵‐C₅H₅)₂Cl₂] and [Ti(η⁵‐C₅H₄Me)₂Cl₂] (1:1) in the presence of two equivalents of NEt₃ yielded the complexes [SnMe₂(dmox)] (1), [Ti(η⁵‐C₅H₅)₂(dmox)] (2) and [Ti(η⁵‐C₅H₄Me)₂(dmox)] (3), respectively. 1–3 have been characterized by spectroscopic methods; in addition, complex 3 has been determined by X‐ray diffraction studies. Furthermore, structural studies based on density functional theory calculations of 1 and 2 have been carried out. The cytotoxic activity of 1–3 was tested against the tumour cell lines human adenocarcinoma HeLa, human myelogenous leukaemia K562 and human malignant melanoma Fem‐x. The results of this study show a higher cytotoxicity of the tin(IV) complex (1) in comparison to their titanium(IV) counterparts (2 and 3) as well as an improvement in the cytotoxic activity of compounds 2 and 3 compared to their titanocene(IV) dichloride analogues [Ti(η⁵‐C₅H₅)₂Cl₂] and [Ti(η⁵‐C₅H₄Me)₂Cl₂]. In view of the relatively high cytotoxicity of compound 1, a detailed study on the effects of the in vitro treatment of cancer cell lines using this compound was carried out. Thus cell cycle experiments on all the studied cell lines treated with 1 show that this complex seems to cause disturbances in the G1 phase of HeLa, and in the G1 and G2/M phases of Fem‐x cell line, while almost no disturbances were observed in the cycle of K562 cells treated with 1. Finally, DNA laddering method showed that treatment of the HeLa and Fem‐x cell lines with IC₉₀ doses of 1 resulted in the induction of apoptosis. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Cytotoxicity of Arene‐Ru Compounds Containing 4‐Nitroaniline or 2‐Halogenated 4‐Nitroaniline

The compounds [(η⁶‐p‐cymene)RuCl₂(4‐nitroaniline)] and [(η⁶‐p‐cymene)RuCl₂(2‐halogen‐4‐nitroaniline)] were synthesized and characterized by various means. The [(η⁶‐p‐cymene)RuCl₂(4‐nitroaniline)] and [(η⁶‐p‐cymene)RuCl₂(2‐fluoro‐4‐nitroaniline)] compounds were determined by X‐ray diffraction, appearing in a distorted piano‐stool type of arrangement with similar bond lengths and angles around the ruthenium. The compounds exhibited moderate to strong in vitro cytotoxicity against A549 and MCF‐7 human cancer cells. Substitution of heavy halogen atom on the ortho position of para‐nitroaniline weakened the cytotoxicity against both of MCF‐7 and A549, except the cases of fluorine substitution for hydrogen atom regarding A549 and bromine substitution for chlorine atom regarding MCF‐7, which showed minor deviation.     

1,2,4‐Triazole‐based N‐heterocyclic carbene complexes of gold(I): synthesis,characterization and biological activity

Two gold(I) complexes of the (NHC)AuX type bearing a triazole‐based N‐heterocyclic carbene (NHC) ligand (1‐tert‐butyl‐4‐(4‐methylphenyl)‐3‐phenyl‐1H‐1,2,4‐triazol‐4‐ium‐5‐ylidene) and various halide ligands (X = Br, I) were synthesized and characterized in solution using NMR spectroscopy as well as in the solid state using X‐ray diffraction techniques. The cytotoxic properties of both compounds and the precursor, (NHC)AuCl, were screened against a panel of human tumour cell lines including liver cancer (HepG2), cervical cancer (HeLa S3) and leukaemia (CCRF‐CEM, HL‐60) and compared to cisplatin and auranofin. It was found that the activities of the chloro and bromo derivatives were generally superior to that of cisplatin and slightly less effective compared to auranofin, except for HepG2 cells where auranofin was not as effective. In addition, the ability to induce membrane phosphatidyl serine externalization as a hallmark of apoptosis in CCRF‐CEM leukaemic cells was investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,structure and in vitro cytotoxicity of platinum(II) complexes containing eugenol and a quinolin‐8‐ol‐derived chelator

The synthesis of potassium (η²‐4‐allyl‐2‐methoxyphenol)trichloridoplatinate(II), K[PtCl₃(C₁₀H₁₂O₂)], ( 1 ), starting from Zeise's salt and Ocimum sanctum L. oil has been optimized. Starting from ( 1 ), three new platinum(II) complexes, namely (η²‐4‐allyl‐2‐methoxyphenol)chlorido(2‐methylquinolin‐8‐olato‐κ²N ,O )platinum(II), ( 2 ), (η²‐4‐allyl‐2‐methoxyphenol)chlorido(5‐nitroquinolin‐8‐olato‐κ²N ,O )platinum(II), ( 3 ), and (η²‐4‐allyl‐2‐methoxyphenol)chlorido(5,7‐dichloroquinolin‐8‐olato‐κ²N ,O )platinum(II), [Pt(C₉H₄Cl₂NO)Cl(C₁₀H₁₂O₂)], ( 4 ), containing eugenol and a quinolin‐8‐ol derivative (R‐OQ), have been synthesized and characterized by elemental analyses, MS, IR, ¹H NMR and NOESY spectra. For ( 1 ) and ( 4 ), single‐crystal X‐ray diffraction studies were also carried out. Complexes ( 2 )–( 4 ) show good inhibiting abilities on three human cancer cell lines, i.e. KB, Hep‐G2 and LU, with IC₅₀ values of 1.42–17.8 µM . Complex ( 3 ) gives an impressively high activity against KB, Hep‐G2, LU and MCF‐7, with IC₅₀ values of 1.42–4.91 µM , which are much lower than those of cisplatin and some other platinum(II) complexes.     

Effect of solvent coordination on the structure of β‐diketone‐based vanadyl complexes and assessment of in vitro antidiabetic activity and cytotoxicity

The physicochemical properties, thereby the biological efficacy, of metal complexes are affected based on their structure and geometry that vary in the presence of coordinating and non‐coordinating solvents. To investigate this, in the present work, we synthesized three hitherto unreported β‐diketone‐based oxovanadium(IV) complexes, namely [VO(tfdmh)₂] (tfdmh =1,1,1‐trifluro‐5,5‐dimethyl‐2,4‐hexanedione), [VO(dmh)₂] (dmh = 2,2‐dimethyl‐3,5‐hexanedione) and [VO(dbm)₂] (dbm = 1,3‐diphenylpropane‐1,3‐dione), and characterized them using electron paramagnetic resonance, UV–visible, Fourier transform infrared and electrospray ionization mass spectroscopies and single‐crystal X‐ray diffraction. The structural changes in the presence of dichloromethane, dimethylsulfoxide and dimethylformamide were analysed using spectroscopic techniques. Further, in vitro glucose uptake efficacy and cytotoxicity were assessed using C2C12 (rat skeletal muscle) and HeLa (human cervical cancer) cell lines, respectively.