Anticancer activity of Ni(II) and Zn(II) complexes based on new unsymmetrical salophen-type ligands: synthesis, characterization and single-crystal X-ray diffraction.

The discovery of new coordination compounds with anticancer properties is an active field of research due to the severe side effects of platinum-based compounds currently used in chemotherapy. In the search for new agents for the treatment of cancer, unsymmetrical N2O2-tetradentate ligand (H2L1 and H2L2) and their Ni(II) and Zn(II) asymmetric complexes (NiII-L1-2 and ZnII-L1-2) have been synthesized and fully characterized. 1H NMR studies revealed that the ligands and complexes were stable in mixtures of DMSO : D2O (9 : 1). Complementary UV-Vis studies confirmed that ZnII derivatives also exhibit high stability in mixtures DMSO : buffer (6 : 4) after 24 h. Single-crystal X-ray diffraction studies confirmed the molecular structures of H2L1, H2L2, NiII-L1, and NiII-L2. At the molecular level, complexes were completely planar without significant distortions of the square-planar geometry according to τ4 parameter. Furthermore, the crystalline structures revealed non-classical intermolecular interactions of the C-H⋯O and the Ni⋯Ni type. The ligands and complexes were screened against the human osteosarcoma (MG-63), human colon cancer (HCT-116), breast cancer (MDA-MB-231) cell lines, and non-cancerous cells (L929). H2L1 and H2L2 ligands not caused cytotoxic effects at a concentration of 100 µM, while NiII-L2, ZnII-L1, and ZnII-L2 complexes induce cytotoxic effects in all cell lines. NiII-L2 was a more active complex against MG-63 (3.9 ± 1.5) and HCT-116 (3.4 ± 1.7) cell lines with IC50 values in the low micromolar range. In addition, this compound was 10-, 5-, and 11-fold more potent than cisplatin in MG-63 (39 ± 1.8), HCT-116 (17.2), and MDA-MB-231 (131 ± 18), respectively. Three complexes exhibited great selectivity for tumoral cells with SI values ranging from 1.6 to 7.4.

Ferrocene-based nitroheterocyclic sulfonylhydrazones: design, synthesis, characterization and trypanocidal properties.

A series of new ferrocenyl nitroheterocyclic sulfonylhydrazones (1a-4a and 1b-2b) were prepared by the reaction between formyl (R = H) or acetyl (R = CH3) nitroheterocyclic precursors [4/5-NO2(C5H2XCOR), where X = O, S)] and ferrocenyl tosyl hydrazine [(η5-C5H5)Fe(η5-C5H4SO2-NH-NH2)]. All compounds were characterized by conventional spectroscopic techniques. In the solid state, the molecular structures of compounds 1a, 2b, and 3a were determined by single-crystal X-ray diffraction. The compounds showed an E-configuration around the C=N moiety. Evaluation of trypanocidal activity, measured in vitro against the Trypanosoma cruzi and Trypanosoma brucei strains, indicated that all organometallic tosyl hydrazones displayed activity against both parasite species with a higher level of potency toward T. brucei than T. cruzi. Moreover, the biological evaluation showed that the 5-nitroheterocyclic derivatives were more efficient trypanocidal agents than their 4-nitroheterocyclic counterparts.

Metal-Organic Compounds as Anticancer Agents: Versatile Building Blocks for Selective Action on G-quadruplexes.

BACKGROUND: Since the 1980s, cancer research has focused primarily on developing new therapeutic agents targeting DNA alterations rather than understanding cancer as an integrated system composed of several modules. In this sense, G-quadruplex (G4) nucleic acids are a promising target for drug development for cancer therapy since they exist in the chromosomal telomeric sequences and the promoter regions of numerous genes. The G4 structures within telomeric DNA can inhibit telomerase activity and prevent the proliferation and immortalization of cancer cells. Furthermore, such G4 systems within the promoter regions of oncogenes can inhibit the transcription and expression of the oncogene. OBJECTIVE: The rational design of small molecules such as organic ligands and their metal- organic derivative compounds can stabilize G4 structures through different binding modes on several G4 DNA topologies. Metal-based compounds have demonstrated their competitiveness compared to organic molecules to distinguish G4 over the DNA duplex owing to their convenient coordination features, positive charge, and electron density promoted by organic ligand. RESULTS: This article is a comprehensive review of metal compounds G4-binders and their structural features that confer them the ability to recognize G-quartets and stabilize several DNA G4s. CONCLUSION: This stabilization can be achieved through extended square aromatic surfaces, increased hydrophobicity, different auxiliary ligands, axially coordinated ligands, and the nature of the metal center.

Evaluation of trypanocidal properties of ferrocenyl and cyrhetrenyl N-acylhydrazones with pendant 5-nitrofuryl group.

Four N-acylhydrazones of general formulae [R1-C(O)-NH-N=C(R2)(5-nitrofuryl)] with (R1 = ferrocenyl or cyrhetrenyl and R2 = H or Me) are synthesized and characterized in solution and in the solid-state. Comparative studies of their stability in solution under different experimental conditions and their electrochemical properties are reported. NMR studies reveal that the four compounds are stable in DMSO­d6 and complementary UV-Vis studies confirm that they also exhibit high stability in mixtures DMSO:H2O at 37 °C. Electrochemical studies show that the half-wave potential of the nitro group of the N-acylhydrazones is smaller than that of the standard drug nifurtimox and the reduction process follows a self-protonation mechanism. In vitro studies on the antiparasitic activities of the four complexes and the nifurtimox against Trypanosoma cruzi and Trypanosoma brucei reveal that: i) the N-acylhydrazones have a potent inhibitory growth activity against both parasites [EC50 in the low micromolar (in T. cruzi) or even in the nanomolar (in T. brucei) range] and ii) cyrhetrenyl derivatives are more effective than their ferrocenyl analogs. Parallel studies on the L6 rat skeletal myoblast cell line have also been conducted, and the selectivity indexes determined. Three of the four N-acylhydrazones showed higher selectivity towards T. brucei than the standard drug nifurtimox. Additional studies suggest that the organometallic compounds are bioactivated by type I nitroreductase enzymes.

Spectroscopic Study of the E/Z Photoisomerization of a New Cyrhetrenyl Acylhydrazone: A Potential Photoswitch and Photosensitizer†.

The new cyrhetrenyl acylhydrazone [(CO)3 Re(η5 -C5 H4 )-C(O)-NH-N = C(CH3 )-(2-C4 H2 S-5-NO2 )] (E-CyAH) has been designed, synthesized and fully characterized to study the effect of having a cyrhetrenyl fragment (sensitizer) covalently bonded to an acylhydrazone moiety (switch), on its photophysical and photochemical properties. The crystal structure reveals that E-CyAH adopts an E-configuration around the iminic moiety [-N = C(CH3 )]. The absorption spectrum of E-CyAH displays two bands at 270 and 380 nm, which are mainly ascribed to π â†’ π* intraligand (IL) and dπ  â†’ π* metal-to-ligand charge transfer (MLCT) transitions, being consistent with DFT/TD-DFT calculations. Upon 365 nm irradiation, E-CyAH photoisomerizes to Z-CyAH, as evidenced by UV-Vis and 1 H-NMR spectral changes, with a quantum yield value ΦE -CyAH → Z -CyAH of 0.30. Z-CyAH undergoes a first-order thermal back-isomerization process, with a relatively short half-life τ1/2 of 277 min. Consequently, E-CyAH was quantitatively recovered after 24 h, making it a fully reversible T-type molecular photoswitch. This remarkable behavior allows us to measure the individual photophysical properties for both isomers. In addition, E-CyAH and Z-CyAH efficiently photosensitize the generation of singlet oxygen (O2 (1 Δg )) with good yield (ΦΔ  = 0.342).