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A series of thirty novel tetracarboxylatoplatinum(IV) complexes in trans-configuration featuring combinations of mixed ammine, methylamine, dimethylamine, and cyclopentylamine ligands as well as acetato/propanoato and trifluoropropanoato ligands was synthesised. The platinum(IV) complexes were characterised by one- and two-dimensional multinuclear NMR spectroscopy (1H, 13C, 15N, 19F, 195Pt), ESI-MS, elemental analysis, and X-ray diffraction. Additional parameters such as reduction behaviour and lipophilicity were measured via NMR spectroscopy and RP-HPLC, revealing slow reduction and a broad spectrum of log kw values in line with the respective ligand combination. In order to determine structure–activity relationships, cytotoxic activity was evaluated via the MTT assay in three human cancer cell lines (CH1/PA-1, ovarian teratocarcinoma, SW480, colon adenocarcinoma, A549, non-small-cell lung carcinoma). The induction of apoptosis and necrosis was determined in SW480 cells via the flow-cytometric annexin V/PI assay. In general, a tendency of higher lipophilicity leading to higher cytotoxicity was noticed. In contrast, lipophilicity alone plays a subordinate role for the induction of apoptosis, which strongly depends on the combination of am(m)ine and trifluoropropanoato ligands. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and biological activity of tungstenocenes with varying biologically active (O,O–), (S,O–) and (N,O–) chelates are described. Complexes were characterized by 1H and 13C NMR, elemental analysis, ESI-mass spectrometry, FT-IR spectroscopy and X-ray diffraction analysis. The aqueous stability was studied by UV/Vis spectroscopy and the WIV to WV process by cyclic voltammetry. The cytotoxicity was determined by the MTT assay in A549, CH1/PA-1 and SW480 cancer cells as well as in IMR-90 human fibroblasts. Extensive biological evaluation was performed in three other human cancer cell lines (HCT116, HT29 and MCF-7) in monolayer and multicellular tumor spheroid cultures to better understand the mode of action. Lead compounds showed promising in vitro anticancer activity in all cancer cell lines. Further studies yielded important insights into apoptosis induction, ROS generation, different patterns in metal distribution (detected by LA-ICP-TOF-MS), changes in KI67 (proliferation marker) expression and DNA interactions. The results based on qualitative and quantitative research designs show that complexes containing (S,O–) chelates are more active than their (O,O–) and (N,O–) counterparts. The most striking results in spheroid models are the high antiproliferative capacity and the different distribution pattern of two complexes differing only in a W–S or W–O bond. [ABSTRACT FROM AUTHOR]

Based on their drug delivery properties and activity against tumors, we combined PAMAM dendrimers with various platinum(IV) complexes in order to provide an improved approach of anticancer treatment. Platinum(IV) complexes were linked to terminal NH2 moieties of PAMAM dendrimers of generation 2 (G2) and 4 (G4) via amide bonds. Conjugates were characterized by 1H and 195Pt NMR spectroscopy, ICP-MS and in representative cases by pseudo-2D diffusion-ordered NMR spectroscopy. Additionally, the reduction behavior of conjugates in comparison to corresponding platinum(IV) complexes was investigated, showing a faster reduction of conjugates. Cytotoxicity was evaluated via the MTT assay in human cell lines (A549, CH1/PA-1, SW480), revealing IC50 values in the low micromolar to high picomolar range. The synergistic combination of PAMAM dendrimers and platinum(IV) complexes resulted in up to 200 times increased cytotoxic activity of conjugates in consideration of the loaded platinum(IV) units compared to their platinum(IV) counterparts. The lowest IC50 value of 780 ± 260 pM in the CH1/PA-1 cancer cell line was detected for an oxaliplatin-based G4 PAMAM dendrimer conjugate. Finally, in vivo experiments of a cisplatin-based G4 PAMAM dendrimer conjugate were performed based on the best toxicological profile. A maximum tumor growth inhibition effect of 65.6% compared to 47.6% for cisplatin was observed as well as a trend of prolonged animal survival. [ABSTRACT FROM AUTHOR]

Fine-tuning of the properties of a recently reported 1,3-indandione-based organoruthenium complex is attempted to optimize the stability under physiological conditions. Previous work has shown its capacity of inhibiting topoisomerase IIα; however, fast aquation leads to undesired reactions and ligand cleavage in the blood stream before the tumor tissue is reached. Exchange of the chlorido ligand for six different N-donor ligands resulted in new analogs that were stable at pH 7.4 and 8.5. Only a lowered pH level, as encountered in the extracellular space of the tumor tissue, was capable of aquating the complexes. The 50% inhibitory concentration (IC50) values in three human cancer cell lines differed only slightly, and their dependence on the utilized leaving group was smaller than what would be expected from their differences in cellular accumulation, but in accordance with the very minor variation revealed in measurements of the complexes' lipophilicity. [ABSTRACT FROM AUTHOR]

By controlled Anderson type rearrangement reactions complexes of the general formula trans-[OsIVCl4(Hazole)2], where Hazole = 1H-pyrazole, 2H-indazole, 1H-imidazole, and 1H-benzimidazole, have been synthesized. Note that 2H-indazole tautomer stabilization in trans-[OsIVCl4(2H-indazole)2] is unprecedented in coordination chemistry of indazole. The metal ion in these compounds possesses the same coordination environment as ruthenium(III) in (H2ind)[RuIIICl4(Hind)2], where Hind = 1H-indazole, (KP1019), an investigational anticancer drug in phase I clinical trials. These osmium(IV) complexes are appropriate precursors for the synthesis of osmium(III) analogues of KP1019. In addition the formation of an adduct of trans-[OsIVCl4(Hpz)2] with cucurbit[7]uril is described. The compounds have been comprehensively characterized by elemental analysis, EI and ESI mass spectrometry, spectroscopy (IR, UV-vis, 1D and 2D NMR), cyclic voltammetry, and X-ray crystallography. Their antiproliferative acitivity in the human cancer cell lines CH1 (ovarian carcinoma), A549 (nonsmall cell lung carcinoma), and SW480 (colon carcinoma) is reported. [ABSTRACT FROM AUTHOR]

• Synthesis of organometallic selenopyridone complexes. • Dimer formation in aqueous solution. • Stability investigations. • Determination of cytotoxic potential. A series of seven piano–stool complexes featuring selenopyridones as Se,O -chelating ligands was synthesized and characterized. The resulting complexes bear either a p -cym Ru/Os or Cp* Rh/Ir fragment attached to a bidentate selenopyridone ligand. In accordance with recent findings for closely related thiopyridone complexes, dimerization in protic solvents was observed for these compounds. However, these organometallics revealed surprises regarding stability, as well as biological activity. In contrast to analogous thiopyridone organometallics, some of the synthesized complexes were prone to quick ligand dissociation. However, four examples exhibited sufficient stability in aqueous solution to justify further biological investigations. Therefore, MTT assays were carried out for the stable derivatives in three different cancer cell lines. Cytotoxicity trends based on the utilized metal center of the organometallic moiety were observed and compared to the corresponding thio-analogs. [ABSTRACT FROM AUTHOR]

Half-sandwich organometallic complexes featuring Ru(II), Os(II) and Rh(III) metal centers and naturally occurring bidentate 2-hydroxy-[1,4]-naphthoquinone ligands (lawsone and phthiocol) have been synthesized and characterized in both solid state and solution phase by analytical, spectroscopic, electrochemical and single crystal X-ray diffraction techniques. Comparative studies revealed the influence of the respective metal center (Ru, Os, Rh), leaving group (Cl, Br, I) and arene (p -cymene, toluene, pentamethylcyclopentadienyl), as well as the naphthoquinone ligand on the structural properties and solution speciation. Additionally, cytotoxicity was tested in SW480, CH1/PA-1 and A549 human cancer cell lines showing a broad range of IC 50 values. Image 1 • Single crystal X-ray structure of five half-sandwich phthiocol complexes. • Anticancer activity in three human cancer cell lines. • Solution stability of Ru(II) and Rh(III) complexes of 2-hydroxy-[1,4]-naphthoquinones. • Comparison with other bidentate (O,O) ligands. [ABSTRACT FROM AUTHOR]