Influence of Co (III) and Ru (III) ion coordination on the accessibility of different lapachol oxidation states

Lapachol is a natural product that has potential biological activity due it is several mechanisms in the cell, including redox cycles involving the generation of free radicals and other reactive oxygen species (ROS). Metal ions can bind to lapachol which may exhibit different oxidation states (quinone, semiquinone and catechol) and this binding ability is important role of quinone in biological system. We proposed the new cobalt (III) and ruthenium (III) complexes of lapachol aiming to investigate the chemical behavior of trivalente metal center and lapachol as well as these metal complexes can influence in the biological properties. The complexes were characterized using several physicochemical techniques such as elementary analysis, mass spectra, spectroscopic behavior in the infrared and UV–visible region, as well as electrochemical process. The complex formed by the reaction between ruthenium(III) and the lapacholate anion was isolated as RuII-quinone and RuIII-semiquinone, which exhibited valence tautomerism. Both compounds presented cytotoxicity against a murine melanoma cell line (B16/F10). However, the [Ru(lap─)2(NH3)2]+ complex exhibited significant cytotoxic effects as a result of superoxide anion production, determined using the NBT assay.