A Bioactive L-Phenylalanine-Derived Arene in Multitargeted Organoruthenium Compounds: Impact on the Antiproliferative Activity and Mode of Action

Ru-II(eta(6)-arene) compounds carrying bioactive flavonol ligands have shown promising anticancer activity against tumor cells via a multitargeting mode of action, i.e., through interaction with DNA and inhibition of topoisomerase II alpha. By introducing a novel arene ligand based on the amino acid L-phenylalanine (Phe), we aimed to alter the pharmacological properties of the complexes. We report here a series of novel Ru-II(eta(6)-arene)Cl complexes with different substituents on the phenyl ring of the flavonol which should maintain the multitargeting capability of the parent eta(6)-p-cymene (cym) complexes. Studies with selected examples revealed stability in aqueous solution after quickly forming aqua complexes but rapid decomposition in pure DMSO. The reactions with protein and DNA models proceeded quickly and resulted in cleavage of the flavonol or adduct formation, respectively. The compounds were found to be cytotoxic with significant antiproliferative activity in cancer cells with IC50 values in the low mu M range, while not following the same trends as observed for the cym analogues. Notably, the cellular accumulation of the new derivatives was significantly higher than for their respective cym complexes, and they induced. DNA damage in a manner similar to that of cisplatin but to a lesser extent.