Pharmacologically Active Plant Flavonols as Proton Transfer Based Multiparametric Fluorescence Probes Targeting Biomolecules: Perspectives and Prospects

Abstract

Plant flavonols, and related compounds of the flavonoid group, are attracting enormous attention as novel therapeutic drugs for free radical mediated and other human diseases. Their high potency and low systemic toxicity make them viable alternatives to conventional therapeutics. On a different scenario, from the spectroscopic context, flavonols have emerged as one of the best known class of molecules exhibiting ultrafast excited state intramolecular proton transfer (ESIPT) leading to ‘two color’ fluorescence emissions which are exquisitely sensitive to environmental perturbations. Regarding therapeutic aspects of flavonols, the question of their physiological targets and the mode of interaction with such targets loom large This article presents perspectives, illustrating the potential usefulness of flavonols as their own fluorescent ‘reporters’ for noninvasive sensing of their interactions with representative biologically relevant targets encompassing carrier proteins, duplex and quadruplex DNA, and model and natural biomembranes. Representative and recent findings from our laboratory, exemplifying novel uses of flavonols as multiparametric fluorescence probes, are appropriately highlighted.