4-Azaindole (1H-pyrrolo[3,2-b]pyridine; 4aza) and its N1-alkylated derivative N1-isopropyl-4-azaindole (1-(propan-2-yl)-1H-pyrrolo[3,2-b]pyridine; ip4aza) have been used for the preparation of the cis-diiodido-platinum(II) complexes cis-[Pt(4aza)2I2] (1), cis-[PtI2(ip4aza)2] (2), cis-[Pt(4aza)I2(NH3)] (3) and cis-[PtI2(ip4aza)(NH3)] (4). The prepared complexes were thoroughly characterized (e.g., multinuclear NMR spectroscopy and ESI mass spectrometry) and their in vitro cytotoxicity was assessed at human ovarian carcinoma (A2780), cisplatin-resistant ovarian carcinoma (A2780R) and colon carcinoma (HT-29) cell lines, where they showed, in some cases, significantly higher activity than the used reference-drug cisplatin. The results of in vitro cytotoxicity testing at the A2780 and A2780R cells indicated that alkylation of the 4-azaindole moiety at the position of the N1 atom had a positive biological effect, because the ip4aza-containing complexes 2 and 4 showed significantly (p < 0.005) higher cytotoxicity than 4aza-containing analogues 1 and 3. The resistance factors (A2780R/A2780 model) equalled 0.8-1.4, indicating the ability of complexes 1-4 to overcome the acquired resistance of the A2780 cells against cisplatin. Complexes 1 and 2 revealed low toxicity against primary culture of human hepatocytes. The flow cytometry studies of the A2780 cell cycle modification showed that complexes 1-4 induce different cell cycle perturbations as compared with cisplatin, thus suggesting a different mechanism of their antitumor action.

Biologically Active Complexes and Molecular Magnets Regional Centre of Advanced Technologies and Materials Faculty of Science Palacký University in Olomouc Šlechtitelů 27 783 71 Olomouc Czech Republic

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