Spectroscopic Characterization,<i>In Vitro</i>Cytotoxicity, and Antioxidant Activity of Mixed Ligand Palladium(II) Chloride Complexes Bearing Nucleobases

Abstract

Mixed-ligand palladium(II) chloride complexes bearing the nucleobases, adenine (Ad), cytosine (Cyt), and guanine (Gua), have been synthesized and characterized by UV-vis spectrophotometric methods, magnetic susceptibility, molar conductivity, elemental analysis, FTIR, and 1 H-NMR. The complexes were found to have the composition cis-[PdCl 2 (Gua)(Cyt)], cis-[PdCl 2 (Ad)(Cyt)], and cis-[PdCl 2 (Ad)(Gua)]. A four-coordinated square-planar geometry is proposed for these Pd(II) complexes based on magnetic evidence and electronic spectra. The complexes as well as the free nucleobase ligands were tested for their in vitro cytotoxicity on human promyelocytic leukemia (HL60) and human histiocytic leukemia (U937) cell lines. cis-[PdCl 2 (Ad)(Gua)] showed IC 50 values of 11.29 ± 2.91 and 8.31 ± 1.44 μ M against HL60 and U937, respectively, which was higher than that of the positive control (curcumin) against U937. The complexes also showed significant antioxidant activity when tested against 2,2-diphenyl-1-picrylhydrazylradical (DPPH).