Novel Au(III) complexes of aminoquinoline derivatives: crystal structure, DNA binding and cytotoxicity against melanoma and lung tumour cells

Three novel gold(III) complexes [Au(Quinpy)Cl]Cl (1), [Au(Quingly)Cl]Cl (2) and [Au(Quinala)Cl]Cl (3) [N-(8-quinolyl)pyridine-2carboxamide = HQuinpy; N-(8-quinolyl)glycine-carboxamide = HQuingly; N-(8-quinolyl)-L-alanine-carboxamide = HQuinala] have been synthesized and characterized. The crystal structures of complexes 2 and 3 reveal that Au(III) is coordinated by three N atoms from the ligand and one Cl- anion. Complex 2 crystallized in the monoclinic system while complex 3 crystallized in the orthorhombic system. The complexes were tested against a series of tumour cell lines including B16-BL6, P388, HL-60, A-549 and BEL-7402. The data show that complex 1 is highly cytotoxic against the A-549 cells with an inhibition rate of 94.4% at a concentration of 10^-6 mol L^-1. Complex 3 is active against B16-BL6 with an inhibition rate of 67.52% at a concentration of 10^-7 mol L^-1. The interactions of complexes 1-3 with calf thymus (CT) DNA and 5ʹ-GMP were investigated by UV-vis, fluorescence and ESMS spectroscopies. The data show that the interaction between Au(III) complexes and CT-DNA may be the intercalation effect, and complex 3 forms a 5ʹ-GMP adduct as detected by ESMS.