A mitochondriotropic derivative of quercetin: a strategy to increase the effectiveness of polyphenols.

Mitochondria-targeted compounds are needed to act on a variety of processes that take place in these subcellular organelles and that have great pathophysiological relevance. In particular, redox-active molecules that are capable of homing in on mitochondria provide a tool to intervene on a major cellular source of reactive oxygen species and on the processes they induce, notably the mitochondrial permeability transition and cell death. We have linked the 3-OH of quercetin (3,3',4',5,7-pentahydroxy flavone), a model polyphenol, and the triphenylphosphonium moiety, a membrane-permeant cationic group, to produce proof-of-principle mitochondriotropic quercetin derivatives. The remaining hydroxyls were sometimes acetylated to hinder metabolism and improve solubility. The new compounds accumulate in mitochondria in a transmembrane potential-driven process and are only slowly metabolised by cultured human colon cells. They inhibit mitochondrial ATPase activity much as quercetin does, and are toxic for fast-growing cells.