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

A copper complex [Cu(HPBM)( l -Phe)(H 2 O)]·ClO 4 (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) × 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 IC 50 values range from 5.7 ± 0.1 to 8.3 ± 0.6 µM. Free HPBM displays no cytotoxic activity against the selected cancer cells, with IC 50 values more than 100 µM. 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 Ca 2+ 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.