Excited state proton transfer of natural flavonoids and their chromophores in duplex and tetraplex DNAs.

Fisetin (3,7,3',4'-tetrahydroxyflavone) and quercetin (3,5,7,3',4'-pentahydroxyflavone) are the bioactive plant flavonoids that are potentially useful therapeutic drugs for the treatment of a broad spectrum of diseases, including atherosclerosis, cardiovascular disease, obesity, hypertension, and cancer. 3-Hydroxyflavone (3HF) and 7-hydroxyflavone (7HF) are the synthetic chromophores of fisetin and quercetin. We have exploited dual luminescence properties of fisetin and quercetin along with 3-HF and 7HF to examine their efficacy of binding and compare their interactions with DNA, which is one of the macromolecular targets of flavonoids in physiological systems.