Synthesis, crystal structure, DNA binding, and anticancer activity of the cobalt(II), nickel(II), and copper(II) complexes of 9-benzothiazolanthrahydrazone

Abstract

In the present study, we synthesized and extensively characterized a novel ligand, 9-THA, based on 9-benzothiazolanthrahydrazone, along with its three corresponding transition metal complexes: 9-THA-Co (1), 9-THA-Ni (2), and 9-THA-Cu (3). The crystallographic analysis revealed distinct coordination geometries - six-coordinate for 9-THA-Co and 9-THA-Ni, binding three and two 9-THA ligands, respectively, and four-coordinate for 9-THA-Cu, binding one 9-THA ligand. In vitro anticancer screening demonstrated that 9-THA-Cu exhibited significant growth inhibition in HeLa-229, NCI-H460, and SK-OV-3 cancer cells with IC50 values of 12.10 ± 0.54, 12.12 ± 0.58, and 17.65 ± 0.66 μM, respectively. Moreover, it displayed comparable cytotoxicity to cisplatin on HL-7702 normal liver cells. In contrast, 9-THA and 9-THA-Co/9-THA-Ni did not exhibit significant growth inhibition in the tested cancer cells, suggesting that Cu(II) played a pivotal role in its anticancer mechanism. Further investigation revealed the intercalative DNA binding mode of 9-THA-Cu by UV–Vis and fluorescent spectral analyses. It also exhibited competitive binding with two typical DNA intercalators, Gel-red (GR) and ethidium bromide (EB). Cell cycle and cell apoptosis experiments indicated that 9-THA-Cu at a concentration of 22 μM could induce cell cycle arrest in the S phase in 40 % of HeLa-229 cancer cells. Simultaneously, it induced 33.2 % apoptosis in HeLa-229 cells, suggesting that 9-THA-Cu may employ multiple mechanisms to exert its anticancer effects.