Radicalic cleavage pathway and DNA docking studies of novel chemotherapic platinum agent of 5,6-di-2-ithienyl-2,3-dihydropyrazine

Abstract

A new Pt(II) complex of the general formula ([PtCl2(L)]·H2O), where L is 5,6-di-2-thienyl-2,3-dihydropyrazine is synthesized as a potential antitumor agent and its structure is elucidated using a variety of physical and chemical procedures. DNA attaching ability of the complex is studied spectroscopically. UV and fluorometric titration, viscometric measurements and thermal decomposition studies agreed that two binding mode of actions, covalent and non-covalent bindings, are possible simultaneously. DNA helix cleavage studies clearly indicated OH• radical pathway in the presence of the reducing agent. Quantum mechanical calculations are carried out to call the minimum energy structures of the ligand and the complex, and to determine the FTIR, 1H NMR and UV–Vis spectra using the density functional theory (DFT) at the B3LYP/LANL2DZ level of theory. Calculated geometrical parameters for the complex indicated a square-planar structure around the metallic center through the dithiopyridyl ring and two chlorine atoms. The minimum energy structure of the complex obtained from DFT conformational analysis is used in docking studies to investigate complex-DNA binding mechanisms. The complex interacts with DNA through three different mechanisms, namely, intercalation, covalent and electrostatic interaction. The most stable mode of interaction with lowest binding energy (–333.6 kcal/mol) was intercalation mode. Comparisons between theoretical and experimental findings are performed and a good agreement is obtained.