Synthesis, characterization and biological activity of Pt(II) and Pt(IV) complexes with 5-methyl-5(4-pyridyl)-2,4-imidazolidenedione.

New platinum(II) and platinum(IV) complexes with 5-methyl-5(4-pyridyl)-2,4-imidazolidenedione and various halogen ions with general formula [PtL(2)X(2)] and [PtL(2)Cl(4)], where L is the organic ligand and X is Cl(-), Br(-), J(-), were synthesized. The molecular formulae of all the complexes were confirmed by elemental analysis, IR, (1)H, (13)C NMR spectral analyses and molar conductivity. The cytotoxic effects of these complexes were examined on some human tumor cell lines. The newly synthesized cis-[PtL(2)Cl(2)] exerted cytotoxic activity against SKW-3, MCF-7, EJ, U-266 tumor cell lines, while cis-[PtL(2)Br(2)], trans-[PtL(2)I(2)] were less active. The higher oxidation state complex cis-[PtL(2)Cl(4)] was inactive in all cell lines but in SKW-3 some augmentation of the cytotoxicity was seen after co-administration of ascorbic acid but not when treated in combination with reduced glutathione or N-acetylcysteine. A DNA-fragmentation analysis revealed that the cytotoxicity of the dichloro analogue, characterized with superior activity compared to the other complexes, is mediated by induction of apoptotic cell death.