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Impact of the Halogen Substitution Pattern on the Biological Activity of Organoruthenium 8‑Hydroxyquinoline Anticancer Agents

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posted on 14.12.2015, 00:00 by Mario Kubanik, Hannah Holtkamp, Tilo Söhnel, Stephen M. F. Jamieson, Christian G. Hartinger
8-Hydroxyquinoline and its derivatives have a broad variety of pharmacological properties, which make them an ideal bioactive building block in the development of metal-based anticancer drugs. In this account we aimed to rationalize the antiproliferative efficacy of organoruthenium compounds featuring 8-hydroxyquinoline-derived ligands and to elucidate structural determinants by using biological assays and bioanalytical methods. By systematically varying the halide substitution pattern at the 5- and 7-positions of the 8-hydroxyquinoline ligand, as well as the halido leaving group, a series of 5,7-dihalido-8-hydroxyquinoline RuII6-p-cymene) complexes were obtained. Studies on their cytotoxic activity revealed the minor impact of the substitution pattern (with the exception of complexes of 8-hydroxyquinoline) on their activity. Notably, the cellular accumulation showed no correlation with the cytotoxic activity, while the nature of the halido leaving group only had a significant influence in the case of the 8-hydroxyquinoline organoruthenium compounds. However, the compounds were shown to be very stable under a wide variety of pH conditions, making them possible candidates for further development as orally active anticancer agents.