No abstract

Six morpholine-(iso)thiosemicarbazone hybrids HL1–HL6 and their Cu(II) complexes with good-to-moderate solubility and stability in water were synthesized and characterized. Cu(II) complexes [Cu(L1–6)Cl] (1–6) formed weak dimeric associates in the solid state, which did not remain intact in solution as evidenced by ESI-MS. The lead proligands and Cu(II) complexes displayed higher antiproliferative activity in cancer cells than triapine. In addition, complexes 2–5 were found to specifically inhibit the growth of Gram-positive bacteria Staphylococcus aureus with MIC50 values at 2–5 μg/mL. Insights into the processes controlling intracellular accumulation and mechanism of action were investigated for 2 and 5, including the role of ribonucleotide reductase (RNR) inhibition, endoplasmic reticulum stress induction, and regulation of other cancer signaling pathways. Their ability to moderately inhibit R2 RNR protein in the presence of dithiothreitol is likely related to Fe chelating properties of the proligands liberated upon reduction.

Maleimide-functionalised Pt(IV) complexes with highly selective binding properties to thiol groups were synthesised as precursors for binding of thiol-containing tumour-targeting molecules like human serum albumin.

Indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (KP1019) and its Na + analogue (KP1339) are two of the most prominent non-platinum antitumor metal complexes currently undergoing clinical trials. After intravenous administration, they are known to bind to human serum albumin (HSA) in a non-covalent manner. In order to elucidate their HSA binding sites, displacement reactions with the established site markers warfarin and dansylglycine as well as bilirubin were monitored by spectrofluorimetry, ultrafiltration−UV-vis spectrophotometry and/or capillary zone electrophoresis. Conditional stability constants for the binding of KP1019 and KP1339 to sites I and II of HSA were determined, indicating that both Ru(III) compounds bind into both sites with moderately to strong affinity (logK 1 ' = 5.3-5.8). No preference for either binding site was found and similar results were obtained for both metal complexes, demonstrating low influence of the counter ion on the binding event.

Complex formation processes of [Ru(η-p-cymene)(HO)] and [Rh(η-CMe)(HO)] organometallic cations with 8-hydroxyquinoline (HQ) ligands were studied in aqueous solution by the combined use of H NMR spectroscopy, UV-visible spectrophotometry and pH-potentiometry. Solution stability, chloride ion affinity and lipophilicity of the complexes were characterized together with the in vitro cytotoxicity against a pair of cancer cell lines, responsive and resistant to classic chemotherapy. The solid phase structure of the [Rh(η-CMe)(8-quinolinolato)(Cl)] complex was characterized by single-crystal X-ray diffraction analysis. In addition to the unsubstituted HQ its 7-(1-piperidinylmethyl) (PHQ) and 5-sulfonate (HQS) derivatives were involved. PHQ has a significant preference for targeting multidrug resistant cancer cell lines, while HQS served as a water soluble model compound. The equilibrium studies revealed the formation of mono[M(L)(HO)] complexes with prominently high solution stability, which predominate at physiological pH even in the micromolar concentration range, and the formation of mixed hydroxido [M(L)(OH)] complexes was characterized by relatively high pK values (8.5-10.3). In comparison to the Rh(η-CMe) species the complexation process with Ru(η-p-cymene) is much slower, and both the pK values and the HO/Cl co-ligand exchange constants are lower by 1-1.5 orders of magnitude. The stability order obtained for these organometallic complexes is as follows: HQS > HQ > PHQ. The cytotoxicity of the ligands and their Ru(η-p-cymene) and Rh(η-CMe) complexes was investigated against MES-SA (human uterine sarcoma) cell line and its multidrug resistant counterpart (MES-SA/Dx5). HQ and its complexes show similar cytotoxicity in both cell lines. In contrast, PHQ and its Rh(η-CMe) complex are more potent against MES-SA/Dx5 cells, while this selectivity could not be observed for the Ru(η-p-cymene) complex.