Effect of Substituents on the Biological Activities of Piano Stool η5-Cyclopentadienyl Rh(III) and Ir(III) Complexes

Experimental and theoretical characterization of the strong effects on DNA stability caused by half-sandwich Ru(II) and Ir(III) bearing thiabendazole complexes

The synthesis and characterization of two half-sandwich complexes of Ru(II) and Ir(III) with thiabendazole as ancillary ligand and their DNA binding ability were investigated using experimental and computational methods. ¹H NMR and acid-base studies have shown that aquo-complexes are the reactive species. Kinetic studies show that both complexes bind covalently to DNA through the metal site and non covalently through the ancillary ligand. Thermal stability studies, viscosity, circular dichroism measurements and quantum chemical calculations have shown that the covalent binding causes breaking of the H-bonding between base pairs, bringing about DNA denaturation and compaction. Additionally, molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) calculations shed light into the binding features of the Ru(II) and Ir(III) complexes and their respective enantiomers toward double-helical DNA, highlighting the important role played by the NˆN ancillary ligand once the complexes are covalently linked to DNA. Moreover, metal quantification in the nucleus of SW480 colon adenocarcinoma cells were carried out by inductively coupled plasma-mass spectrometry (ICP-MS), both complexes are more internalized than cisplatin after 4 h of exposition. However, in spite of the dramatic changes in the helicity of the DNA secondary structure induced by these complexes and their nuclear localization, antiproliferative studies have revealed that both, Ru(II) and Ir(III) complexes, cannot be considered cytotoxic. This unexpected behavior can be justified by the fast formation of aquo-complexes, which may react with components of the cell culture medium or the cytoplasm compartment in such a way that they may become deactivated before reaching DNA.

Synthesis, characterization and biological activities of imidazo[1,2-a]pyridine based gold(III) metal complexes

Five imidazo [1,2-a]pyridine derivatives and their Au(III) complexes were synthesized. The compounds were characterized by ¹H-NMR, ¹³C-NMR, IR, mass, UV-visible, elemental analysis, conductivity and magnetic measurement studies. All the compounds were screened for diverse biological activities to check the effect of coordination of Au(III) with imidazo [1,2-a]pyridine heterocycles. The DNA interaction ability of compounds were studied as the change in absorption maxima and position of HS-DNA in presence of compounds and viscosity measurement due to change in DNA length under the influence of compounds. The computational insight of compound-DNA interaction was taken in docking study. All the results suggest intercalation mode of binding. The cellular level cytotoxic nature of compounds was evaluated using trypan blue dye staining of dead cell in cell viability assay. The smearing of DNA was observed, while DNA extracted from S. pombe cells in presence of complexes was subjected to gel electrophoresis, which shows their toxic effect on DNA. The complexes were evaluated for cytotoxicity on human A549 (Lung adenocarcinoma) cell line by MTT assay (IC₅₀ values). The in vitro cytotoxicity in terms of LC₅₀ value was checked on a simple zoological organism, brine shrimp.