Exploring heterometallic bridged Pt(II)-Zn(II) complexes as potential antitumor agents.

The four novel complexes [{cis-PtCl(NH3)2(µ-4,4'-bipyridyl)ZnCl(terpy)}](ClO4)2 (C1), [{trans-PtCl(NH3)2(µ-4,4'-bipyridyl)ZnCl(terpy)}](ClO4)2 (C2), [{cis-PtCl(NH3)2(µ-pyrazine)ZnCl(terpy)}](ClO4)2 (C3) and [{trans-PtCl(NH3)2(µ-pyrazine)ZnCl(terpy)}](ClO4)2 (C4) (where terpy = 2,2':6',2''-terpyridine) were synthesized and characterized. Acid-base titrations and concentration dependent kinetic measurements for the reactions with biologically relevant ligands such as guanosine-5'-monophosphate (5'-GMP), inosine-5'-monophosphate (5'-IMP) and glutathione (GSH), were studied at pH 7.4 and 37 °C. The binding of the heterometallic bridged cis- or trans-Pt(II)-Zn(II) complexes to calf thymus DNA (CT-DNA) was studied by UV absorption and fluorescence emission spectroscopy and molecular docking. The results indicated that the complexes bind strongly to DNA, through groove binding, hydrogen bonds, and hydrophobic or electrostatic interaction. The possible in vitro DNA protective effect of cis- and trans-Pt-L-Zn complexes has shown that C3 had significant dose-dependent DNA-protective effect and the same ability to inhibit peroxyl as well as hydroxyl radicals. Antiproliferative effect of the complexes, mRNA expression of apoptosis and repair-related genes after treatment in cancer cells indicated that newly synthesized C2 exhibited highly selective cytotoxicity toward colon carcinoma HCT116 cells. Only treatment with trans analog C2 induced effect similar to the typical DNA damaging agent such as cisplatin, characterized by p53 mediated cell response, cell cycle arrest and certain induction of apoptotic related genes. Both cis- and trans-isomers C1 and C2 showed potency to elicit expression of PARP1 mRNA and in vitro DNA binding.

Synthesis of novel palladium(II) complexes with oxalic acid diamide derivatives and their interaction with nucleosides and proteins. Structural, solution, and computational study.

Novel palladium complexes, KH[Pd(obap)]2·3H2O (3) with oxamido-N-aminopropyl-N'-benzoic acid and [Pd(apox)] (4) with N,N'-bis(3-aminopropyl)ethanediamide, were synthesized. Exhaustive synthetic, solution and structural studies of the two Pd(ii) complexes are reported. The binary and ternary systems of the Pd(ii) ion with H2apox or H3obap as primary ligands and nucleosides (Ado or Cyt) as secondary ligands, are investigated in order to better understand their equilibrium chemistry. The relative stabilities of the ternary complexes are determined and compared with those of the corresponding binary complexes in terms of their Δlog K values. The species distribution of all complexes in solution is evaluated. Fluorescence spectroscopy data shows that the fluorescence quenching of HSA is a result of the formation of the [PdL]-HSA complex. The structure of complex 3 is confirmed using X-ray crystallography. The results are compared to those obtained for palladium complexes of similar structures. Density functional theory (DFT) has been applied for modelling and energetic analysis purposes. The nature of the Pd-N(O) bond interaction is analyzed using NBO. We report here docking simulation experiments in order to predict the most probable mechanism of pro-drug-action. The next free binding energy order of the best scores from the [PdL]-DNA docking simulations, cis-[Pt(NH3)2(H2O)2](2+) > [Pd(obap)] > [Pd(mda)], has been observed in the case of DNA alteration. For the ER and cytosolic stress mechanisms the results of the docking simulations to the chaperons Grp78 and Hsc70 are promising for possible applications as potent protein inhibitors (Ki of [Pd(mda)]/GRP78 being ∼66 µM and Ki for [Pd(obap)]/HSC70 being 14.39 µM).

Antiproliferative and proapoptotic activities of methanolic extracts from Ligustrum vulgare L. as an individual treatment and in combination with palladium complex.

The aim of this study is to examine the growth inhibitory effects of methanolic leaf and fruit extracts of L. vulgare on HCT-116 cells over different time periods and their synergistic effect with a Pd(apox) complex. The antiproliferative activity of plant extracts alone or in combination with the Pd(apox) complex was determined using MTT cell viability assay, where the IC(50) value was used as a parameter of cytotoxicity. Results show that antiproliferative effects of L. vulgare extracts increase with extension of exposure time, with decreasing IC(50) values, except for 72 h where the IC(50) values for methanolic leaf extract were lower than for the fruit extract. The Pd(apox) complex alone had a weak antiproliferative effect, but combination with L. vulgare extracts caused stronger effects with lower IC(50) values than with L. vulgare extracts alone. The type of cell death was explored by fluorescence microscopy using the acridin orange/ethidium bromide method. Treatments with plant extracts caused typical apoptotic morphological changes in HCT-116 cells and co-treatments with Pd(apox) complex caused higher levels of apoptotic cells than treatment with plant extracts alone. The results indicate that L. vulgare is a considerable source of natural bioactive substances with antiproliferative activity on HCT-116 cells and which have a substantial synergistic effect with the Pd(apox) complex.