Miroslava Vujčić

Synthesis, characterization and biological activity of three square-planar complexes of Ni(II) with ethyl (2E)-2-[2-(diphenylphosphino)benzylidene]hydrazinecarboxylate and monodentate pseudohalides.

Three square-planar complexes of nickel(II) with the tridentate condensation derivative of 2-(diphenylphosphino)benzaldehyde and ethyl carbazate, and monodentate pseudohalides, have been synthesized. Their crystal structures have been determined. All the complexes showed a significant antifungal activity, while only the azido complex displayed antibacterial activity. All the complexes were cytotoxic to a panel of six tumor cell lines, the azido complex showing a similar activity as cisplatin to leukemia cell line K562 and lower toxicity to normal MRC-5 cells than that anticancer agent. The complexes interfered with cell cycle of tumor cells and induced plasmid DNA cleavage.

Zn(II) complex with 2-quinolinecarboxaldehyde selenosemicarbazone: synthesis, structure, interaction studies with DNA/HSA, molecular docking and caspase-8 and -9 independent apoptose induction

A new Zn(II)-based potential chemotherapeutic agent was synthesized from the ligand 2-quinolinecarboxaldehyde selenosemicarbazone (Hqasesc). Single crystal X-ray diffraction analysis showed that the Zn(II) complex consists of a cation [Zn(Hqasesc)2]2+, two perchlorate anions and one ethanol solvent molecule. The interaction of calf thymus (CT) DNA and human serum albumin (HSA) with the Zn(II) complex was explored using absorption and emission spectral methods, and also has been supported by molecular docking studies. The complex has more affinity to minor DNA groove than major, with no significant intercalation. The HSA interaction studies of the complex revealed the quenching of the intrinsic fluorescence of the HSA through a static quenching mechanism. The antitumor activity of the ligand and the complex against pancreatic adenocarcinoma cell line (AsPC-1) and acute monocytic leukemia (THP-1) cells was evaluated. Both compounds are strong concentration-dependent apoptosis inducers in THP-1 cells. While Hqasesc in AsPC-1 cells induces apoptosis only at the highest concentration, treatment with the Zn complex shows a concentration-dependent apoptotic response, where the treated cells are arrested in the G1-to-S phase accompanied with extensive activation of caspase-8 and -9. These results indicate that the ligand and Zn(II) complex display cell phenotype specific activity.

Anthraquinone–chalcone hybrids: Synthesis, preliminary antiproliferative evaluation and DNA-interaction studies

Novel anthraquinone based chalcone compounds were synthesized starting from 1-acetylanthraquinone in a Claisen-Schmidt reaction and evaluated for their anticancer potential against three human cancer cell lines. Compounds 4a, 4b and 4j showed promising activity in inhibition of HeLa cells with IC50 values ranging from 2.36 to 2.73 μM and low cytotoxicity against healthy MRC-5 cell lines. The effects that compounds produces on the cell cycle were investigated by flow cytometry. It was found that 4a, 4b and 4j cause the accumulation of cells in the S and G2/M phases in a dose-dependent manner and induce caspase-dependent apoptosis. All of three compounds exhibit calf thymus DNA-binding activity. The determined binding constants by absorption titrations (2.65 × 10(3) M(-1), 1.36 × 10(3) M(-1)and 2.51 × 10(3) M(-1) of 4a/CT-DNA, 4b/CT-DNA and 4j/CT-DNA, respectively) together with fluorescence displacement analysis designate 4a, 4b and 4j as strong minor groove binders, but no cleavage of plasmid DNA was observed.

A comparative study of DNA binding and cell cycle phase perturbation by the dinuclear complex of Cd(II) with the condensation product of 2-acetylpyridine and malonic acid dihydrazide N',N'(2) -bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide.

Organometallic Cd(II) compounds have recently attracted attention for their anticancer activity. The interaction of the dinuclear complex of Cd(II) with the condensation product of 2‐acetylpyridine and malonic acid dihydrazide, N′,N′2‐bis[(1E)‐1‐(2‐pyridyl)ethylidene]propanedihydrazide (Cd(II)H2L), with calf thymus DNA (CT‐DNA) was monitored by blue shift in UV–vis spectra of the complex. The binding constant of Cd(II)H2L complex with CT‐DNA was determined (KB = 1.8 × 104 M−1) and was indicative of minor groove binding. Agarose gel electrophoretic changes in mobility of supercoiled and circular forms of pBR322 and pUC18 plasmids in the presence of the complex suggest that conformational changes in the plasmids occur upon binding of the Cd(II)H2L complex. The Cd(II)H2L complex induced perturbation of the cell cycle phase distribution and an increase in the percentage of cells in the sub‐G1 phase of human cervical cancer HeLa cell line and murine melanoma B16 cell line. Immunoblotting analysis showed the overexpression of Bcl‐2 protein with the Cd(II)H2L complex.

Synthesis, cytotoxic activity and DNA-interaction studies of novel anthraquinone-thiosemicarbazones with tautomerizable methylene group.

A series of novel anthraquinone-thiosemicarbazone derivatives in a tautomerizable keto-imine form was synthesized and tested for their in vitro cytotoxic activity against human cancer cells (HeLa, MDA-MB-361, MDA-MB-453, K562, A549) and human normal MRC-5 cells. Several compounds efficiently inhibited cancer cell growth at micromolar concentrations, especially against K562 and HeLa cells. As determined by flow cytometric analysis, anthraquinone-thiosemicarbazone caused significant increase in the number of sub-G1 phase of HeLa cells and apoptosis in a concentration-dependent manner. Also, inhibition of caspase-3, -8, and -9 with specific caspase inhibitors reduced the apoptosis mediated by the tested compounds in HeLa cells. All anthraquinone-thiosemicarbazones exhibit calf thymus DNA-binding activity, but no cleavage of plasmid DNA was observed.

Synthesis, characterization, DFT calculation and biological activity of square-planar Ni(II) complexes with tridentate PNO ligands and monodentate pseudohalides. Part II.

Three square-planar complexes of Ni(II) with condensation derivative of 2-(diphenylphosphino)benzaldehyde and 4-phenylsemicarbazide and monodentate pseudohalides have been synthesized and characterized on the basis of the results of X-ray, NMR and IR spectroscopy and elemental analysis. Investigated complexes exhibited moderate antibacterial and cytotoxic activity. The most pronounced cytotoxic activity (in the range of cisplatin) to HeLa cell line was observed for ligand and all the complexes. Azido complex and ligand induced concentration dependent cell cycle arrest in the S phase, as well as decrease of percentage of cells in G1 phase, without significant increase of apoptotic fraction of cells. The interaction of the azido complex and ligand with CT-DNA results in changes in UV-Vis spectra typical for non-covalent bonding. The observed intrinsic binding constant of azido complex-CT-DNA and ligand-CT-DNA were 3.22 × 10(5) M(-1) and 2.79 × 10(5) M(-1). The results of DNA cleavage experiments showed that azido complex nicked supercoiled plasmid DNA.

Investigation of antitumor potential of Ni(II) complexes with tridentate PNO acylhydrazones of 2-(diphenylphosphino)benzaldehyde and monodentate pseudohalides

Square-planar azido Ni(II) complex with condensation product of 2-(diphenylphosphino)benzaldehyde and Girard’s T reagent was synthesized and its crystal structure was determined. Cytotoxic activity of the azido complex and previously synthesized isothiocyanato, cyanato and chlorido Ni(II) complexes with this ligand was examined on six tumor cell lines (HeLa, A549, K562, MDA-MB-453, MDA-MB-361 and LS-174) and two normal cell line (MRC-5 and BEAS-2B). All the investigated nickel(II) complexes were cytotoxic against all tumor cell lines. The newly synthesized azido complex showed selectivity to HeLa and A549 tumor cell lines compared to the normal cells (for A549 IC50 was similar to that of cisplatin). Azido complex interferes with cell cycle phase distribution of A549 and HeLa cells and possesses nuclease activity towards supercoiled DNA. The observed selectivity of the azido complex for some tumor cell lines can be connected with its strong DNA damaging activity.

Immobilization of cell wall invertase modified with glutaraldehyde for continuous production of invert sugar.

Yeast cell wall invertase (CWI) was modified with dimethyl suberimidate, glutaraldehyde, formaldehyde, and sodium periodate. Retained activity after modification was 45% for CWI modified with formaldehyde, 77% for CWI modified with sodium periodate, 80% for CWI modified with glutaraldehyde, and 115% for CWI modified with dimethyl suberimidate. Chemically modified and native CWIs showed significantly broad pH stability (pH 3-11), whereas after incubations at 50, 60, and 70 °C, CWI modified with glutaraldehyde showed the highest thermostability. Optimum pH for CWI modified with glutaraldehyde was between 4 and 5, whereas optimum temperature was at 60 °C. Comparison to CWI modified with glutaraldehyde after immobilization within alginate beads showed broader pH optimum (4.0-5.5) as well as broader temperature optimum (55-70 °C). Column bed reactor packed with the immobilized CWI modified with glutaraldehyde was successfully used for the 95% inversion of 60% (w/w) sucrose at the flow rate of 3 bed volumes per hour, pH 4.9, and 45 °C. A 1 month productivity of 3844 kg of inverted sugar/kg of the immobilisate was obtained.

Ni(II) complex with bishydrazone ligand: synthesis, characterization, DNA binding studies and pro-apoptotic and pro-differentiation induction in human cancerous cell lines

A new Ni(II) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))bis(hydrazin-1-yl-2-ylidene))bis(3-oxopropanoate) ligand (H2L) was synthesized as a potential chemotherapeutic agent. Polidentate ligand was coordinated to Ni(II) NNN-tridentately, in dianionic form, while monodentate water coordination completed square-planar geometry around metal. Structure in the solution was determined by NMR spectroscopy and the same coordination mode was observed in the solid state using IR spectroscopy and further verified by DFT calculations and electrochemical studies. Thermal stability of 1 was determined in both air and nitrogen atmosphere. Anticancer activity of 1 was investigated on acute monocytic leukemia (THP-1) and pancreatic adenocarcinoma (AsPC-1) cell lines. On THP-1 cells 1 induced powerful apoptotic response (ED50 = 10 ± 3 μM), which was revealed to be only partially caspase-dependent, with activation of caspase-8 as the dominant course. This suggested that experimentally validated covalent binding of 1 to DNA is not the only mechanism responsible for programmed cell death. This was supported with experiments on AsPC-1 cells. Although treatment of those cells with 1 resulted in poor apoptotic response, cell cycle changes showed concentration-dependent shifts indicating a dual mechanism of activity. This study also reviews the results of preliminary biological screening, which demonstrates that 1 displays a unique pattern of anticancer activity with at least two mechanisms involved.

Acidic horseradish peroxidase activity abolishes genotoxicity of common dyes

The aim of this study was to investigate the impact of dyes on DNA before and after enzymatic decolorization by acidic horseradish peroxidase (HRP-A). The comet assay is easy and feasible method widely used to measure DNA damage and repair. The medium-throughput comet assay was employed for assessment of genotoxic effects of 8 dyes in BEAS-2B cells. We have incorporated a digestion with bacterial endonuclease (formamidopyrimidine DNA glycosylase, FPG) to detect oxidized bases in the case of single and double azo dyes, Orange II (OR2) and Amido Black 10B (AB), respectively. This allowed detection 8-oxo-7,8-dihydroguanine, one of most abundant oxidized bases in nuclear DNA. In the case of AB there was no indication of DNA damage, either strand brakes or FPG-sensitive sites before and after decolorization. The OR2 induced DNA damage (in terms of percentage of DNA in comet tails). Also, the frequency of FPG-sensitive sites increased with OR2 concentration. After decolorization no DNA damaging effects was seen at all. The interaction studies of OR2 and AB, before and after decolorization, with calf thymus DNA has been investigated by absorption and fluorescence spectroscopy. The results provide support for the idea that in some cases enzymatic decolorization contributes to lower genotoxicity potential.