Synthesis, characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Two copper(II) complexes with ligands derived from beta-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were synthesized and characterized by microanalysis, infrared, UV-Vis and EPR spectra. The spectroscopically predicted structure of the square-planar copper(II) complex with 2-(1-aminocyclohexyl)-acetic acid C1 was confirmed by single-crystal X-ray analysis. The biological activities (antitumor activities and interaction with DNA) of the compounds were also investigated. The interactions of both complexes with calf thymus (CT) and herring testes (HT) DNA were examined by stopped-flow spectroscopy, by absorption (UV-Vis) and by emission spectral studies (ethidium bromide displacement studies). Both complexes were found to react a bit faster with HT-DNA than with CT-DNA. The obtained binding constants suggested a moderate intercalative binding mode between the complexes and DNA. In addition, fluorescence spectrometry of bovine serum albumin with the complexes showed a good fluorescence quenching of the complexes. The obtained copper(II) complexes have a relatively low cytotoxic effect on murine mammary carcinoma cell line, 4T1, a moderate effect on murine colon carcinoma cell line, CT26, and a relatively high cytotoxicity toward murine lung cancer cells, LLC1.