Studies on the Complexation of Platinum(II) by Some 4-Nitroisoxazoles and Testing the Cytotoxic Activity of the Resulting Complexes

Two novel platinum(II) complexes (1 and 2) were synthesized by the reaction of the appropriate 3,5-dimethyl-4-nitroisoxazole with K(2)PtCl(4) and characterized by elemental analysis, ESI MS spectrometry, (1)H NMR and far-IR spectroscopy. The structure of trans complex 2 was additionally confirmed by X-ray diffraction. The cytotoxicity of the investigated compounds was examined in vitro on three human cancer cell lines (MCF-7 breast, ES-2 ovarian and A-549 lung adenocarcinomas) in both normoxia and hypoxia conditions. LogPs of complexes were measured using the shake-flask method. The trans complex 2 showed much better cytotoxic activity than cisplatin for all the tested cancer cell lines. Cis complex 1 was inferior to its trans isomer against all the cancer lines tested in normoxia conditions but proved superior to the reference cisplatin against the MCF-7 and A549 lines, and showed similar activity to cisplatin against the ES-2 line. To gain additional information that may facilitate the explanation of the pharmacological activity of the tested compounds, cellular platinum uptake and stability in L-glutathione solution were determined for both compounds 1 and 2.