Synthesis, characterization, crystal structures and cytotoxic activity of Pt (II) complexes with N,N-donor ligands in tumor cell lines

Cisplatin is one of the most used chemotherapeutic agents nowadays. However, it presents several and severe side effects. For that, the synthesis of new analogues of cisplatin is crucial to improve the current therapies. In this work, two squared-planar Pt(II) analogues of cisplatin were presented. These analogues included a bidentate ligand molecule with a 3,5-dimethyl-pyrazole ring and a thiazine (DMPzTz) or thiazoline (DMPzTn) ring. The chemical characterization covered single-crystal X-ray diffraction, infrared spectroscopy (IR) and elemental analysis. Their potential anticarcinogenic ability was studied in three different human tumor cell lines, i.e., histiocytic lymphoma (U-937), promyelocytic leukemia (HL-60) and epithelial cervix carcinoma (HeLa) via cytotoxicity assay. The results showed moderate cytotoxic effect of the complexes on leukemic cell lines, with scarce effect on solid tumor cell line HeLa. Lower IC50 values were found for U-937 cell line, being 32.3 +/- 1.2 mu mol/dm3 for PtDMPzTn and 43.0 +/- 1.4 mu mol/dm3 for PtDMPzTz. The comparison with previously synthesized analogues with phenyl substitutions or no substitutions in the pyrazole ring, allows to conclude that the presence of ligands with methyl substituted-pyrazole ring did not improve the effect of the complexes. In addition, the main effect of these potential chemotherapeutic agents is produced by the presence of platinum(II) as metal center, since the free ligands do not show any significant activity.