Redox properties of ruthenium complex with catechol are involved in toxicity to glial cells

Since the biological activity of [Ru-III(NH3)(4)(catechol)](+) has never been tested, its cytotoxicity to glial cells was assayed and correlated with its redox properties. Coordinated catechol oxidizes faster than catechol in the presence of oxygen, but controlled potential electrolysis showed that its oxidation involves only one electron. However, the oxidation of the free ligand by oxygen involves two electrons, which could generate more reactive oxygen species. Indeed, catechol was more cytotoxic than [Ru-III(NH3)4(catechol)](+) complex to human glioblastoma GL-15 cells and also to rat astrocytes. [Ru-III(NH3)4(catechol)](+)-induced cytotoxicity was related to the generation of reactive oxygen species and [Ru-II(NH3)(4)(quinone)](2+). However, other mechanisms should be involved since antioxidant enzymes and deferoxamine only partially protected GL-15 cells.