Ru(II) complexes containing uracil nucleobase analogs with cytotoxicity against tumor cells.

We report on chemistry and cytotoxic studies of four new ruthenium (II) complexes containing uracil derivatives. All compounds are neutral, presenting the formula [Ru(PPh3)2(2TU)2] (1), [Ru(PPh3)2(6m2TU)2] (2), [Ru(dppb)(2TU)2] (3) and [Ru(dppb)(6m2TU)2] (4), where PPh3 = triphenylphosphine; dppb = 1,4-bis(diphenylphosphino)butane, 2TU = 2-thiouracil and 6m2TU = 6-methyl-2-thiouracil. They were characterized using NMR, UV-vis and IR spectroscopies, microanalytical analysis and mass spectrometry. Furthermore, the crystal structures of 1-4 were determined by single-crystal X-ray diffraction. The coordination of 2-thiouracil derivatives with ruthenium increases regions able to carry out hydrogen bonds with the biological targets, such as DNA. We evaluated the interaction of the complexes with DNA by UV/Vis spectrophotometric titration, and as a result, the values of DNA-binding constants are in the range of 0.8-1.8 × 104 M-1. Moreover, the interaction of the complexes with BSA was investigated. In vitro, activities against B16-F10 (mouse melanoma), HepG2 (human hepatocellular carcinoma), HL-60 (human promyelocytic leukemia) and K562 (human chronic myelocytic leukemia) and non-tumor cells: PBMC (human peripheral blood mononuclear cells activated with concanavalin A - human lymphoblast) were carried out. Cytotoxicity assays revealed that complexes (2) and (4) present biological activity against tumor cells comparable with oxaliplatin, the reference platinum drug, revealing that they are promising molecules for developing new antitumor compounds.