DNA binding, crystal structure, molecular docking studies and anticancer activity evaluation of a copper(II) complex

A copper complex [Cu(HPBM)(l-Phe)(H2O)]center dot ClO4 (1) (HPBM = 5-methyl-2-(2'-pyridyl)benzimidazole, l-Phe = l-phenylalanine anion) was synthesized and characterized by elemental analysis, IR, ESI-MS, HR-ESI-MS, ESR spectroscopy, and by X-ray single-crystal analysis. The binding constant of the complex with calf thymus DNA (CT-DNA) was determined as 7.38 (+/- 0.57) x 10(4) M-1. Further studies indicated that the complex interacts with CT-DNA through minor groove binding. The in vitro cytotoxic activities of both the free proligand and the complex against Eca-109, HeLa and A549 cancer cells and normal LO2 cells were evaluated by the MTT method. The IC50 values range from 5.7 +/- 0.1 to 8.3 +/- 0.6 A mu M. Free HPBM displays no cytotoxic activity against the selected cancer cells, with IC50 values more than 100 A mu M. Double staining analysis showed that the complex can induce apoptosis in Eca-109 cells. Comet assays demonstrated that the complex can damage DNA and cause apoptosis. The complex also induces an increase in intracellular reactive oxygen species and a reduction in mitochondrial membrane potential. The complex can also increase the intracellular Ca2+ level and induce release of cytochrome c. The cell cycle arrest was investigated by flow cytometry. The results demonstrate that the complex induces apoptosis in Eca-109 cells through DNA-binding and ROS-mediated mitochondrial dysfunctional pathways.