Synthesis, characterization, theoretical calculations and biochemical evaluation of a novel oxime ligand with complexes

A novel amine containing ketooxime ligand (HBOX) and its Cu(II) and Mn(II) complexes were synthesized, characterized and tested for some of their biological activities. Structural characterization was carried out by elemental analysis, ICP-OES, 1H and 13C NMR, UV–Vis, FT-IR, XRD, TG-DTG, magnetic susceptibility and molar conductivity measurements. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal:ligand ratio was found to be 1:2 and the metal ions were coordinated to the oxime oxygen and amine nitrogen atoms. Furthermore, DFT/B3LYP method with 6-311G(d,p) and LANL2DZ basis sets were used for full optimization of molecular geometries of the ligand and complexes, respectively. The vibrational frequencies, isotropic chemical shifts (1H and 13C NMR), electronic transition absorption wavelengths, HOMO and LUMO analyses and molecular electrostatic potential (MEP) properties of the synthesized molecules have been calculated. The results obtained experimentally were confirmed by the theoretical data which are in good agreement. Inhibitory capacity of the HBOX was investigated against neoangiogenic factors, vascular endothelial growth factor receptor-2 (VEGFR-2) and cyclooxygenase-2 (COX-2) by molecular docking studies. HBOX bound to COX-2 protein with 2 hydrogen bonds at the lowest energy level which indicates the most stabilized form of the protein ligand complex. Complexes were also tested for their catecholase and phenoxazinone synthase-like activities using spectrophotometric procedures. Catecholase and phenoxazinone synthase-like enzyme activities were spectrophotometrically followed by the increase in absorbance at 400 and 433nm resulted from the oxidation reaction of 3,5-di-tert-butylcatechol and 2-aminophenol to 3,5-di-tert-butylquinone and 2-aminophenoxazine-3-one, respectively. According to the calculated kobs values, the Mn(II) complex was found to be more active for both enzymes compared to Cu(II).