Structure, interaction with biomolecules, and cytotoxicity of copper (II) complexes chelating some Schiff base ligands

Abstract

Cancer remains one of the most common diseases worldwide in terms of deaths and claims many lives every day. Transition metal complexes are candidates in the development of anticancer drugs, with cisplatin being used in chemotherapy worldwide. Copper, an endogenous metal, is known for its pronounced redox potential and nucleophilicity, especially when bound to biological molecules. Cu (II) complexes were synthesized containing ethane‐1,2‐diamine as amine moiety and pentane‐2,4‐dione and/or 1‐phenylbutane‐1,3‐dione, pentane‐2,4‐dione and/or 1,1,1‐trifluoropentane‐2,4‐dione or 1,1,1‐trifluoropentane‐2,4‐dione and/or 1‐phenylbutane‐1,3‐dione as β‐diketone moiety. Standard methods were used to confirm the structure of complexes 1–6. X‐ray crystal structure analysis characterized complex 1 containing the ligand ethane‐1,2‐diamine and pentane‐2,4‐dione. The interactions of complexes 1–6 with calf thymus DNA (ct‐DNA) were followed by electronic absorption and fluorescence spectroscopy methods and by viscosity measurements. In contrast, interaction with Salmon Sperm DNA was investigated using the electrophoretic mobility shift assay. The results indicate a moderate affinity of complexes 1–6 for binding to DNA. Gel electrophoresis also shows that the studied complexes have a concentration‐dependent interaction with DNA. Spectroscopic fluorescence techniques were used to monitor the affinity of the complexes for bovine serum albumin (BSA). Complexes 1–6 showed satisfactory binding ability for BSA. Cytotoxicity analyses were performed on the human colorectal carcinoma HCT‐116 and healthy lung fibroblast MRC‐5 cell lines, showing that complex 5 exhibited selectivity between cancer and normal cells, which is critical for drug development.