A potent drug candidature of Cu(II) pyrazino[2,3-f][1,10]phenanthroline complexes with bioactive ligands: synthesis, crystal structures, biomolecular interactions, radical scavenging and cytotoxicities.

A novel ternary copper(II) complexes, - [Cu(py-phen)(asn)(NO ₃ )(H ₂ O)] ( 1 ) and [Cu(py-phen)(trp)(H ₂ O)]NO ₃ ( 2 )- (py-phen: pyrazino[2,3-f][1,10]phenanthroline, asn: asparagine, trp: tryptophan), have been synthesized and characterized by CHN analysis, ESI-MS, FTIR and single-crystal X-ray diffraction techniques. Interaction of the complexes 1 and 2 with CT-DNA has been investigated by absorption spectral titration, EB and Hoechst 33258 displacement assay. The interaction between the complexes 1 and 2 and BSA was investigated by electronic absorption and fluorescence spectroscopy methods. The experimental outcomes indicate that the fluorescence quenching mechanism between the complexes 1 and 2 and BSA is a static quenching process. The Stern-Volmer constants, binding constants, binding sites and the corresponding thermodynamic parameters (ΔG, ΔH, ΔS) of BSA + complex systems were determined at different temperatures. The binding distance between the complexes 1 and 2 and BSA was calculated according to FRET. The effect of the complexes 1 and 2 on the conformation of BSA was also examined using synchronous, two dimensional (2D) and three dimensional (3D) fluorescence spectroscopy. Radical scavenging activity of the complex was determined in terms of EC ₅₀ , using the DPPH and H ₂ O ₂ method. The anticancer activities of the complexes 1 and 2 were investigated using an XTT assay against three cancer cell lines (MCF-7, Caco-2 and A549) and non-tumor cell line (BEAS-2B). Communicated by Ramaswamy H. Sarma.