On the role of pH and temperature on ground – and excited – state proton transfer of hydroxyflavones in lipidic bilayers of lecithin

Abstract

Absorption and emission monitoring of bioactive flavonols, Hydroxyflavones (HFs), (3-HF, 3,6-diHF and 3,7-diHF), to explore their microenvironments as a function of pH and temperature in lipidic bi-layers of lecithin (EYPC), have been studied. The influence of lipidic bi-layers on the − OH groups deprotonation of HFs with several distribution in the vicinity of the polar phosphate groups of EYPC when pH changed as well as the position of −OH groups in the HFs structure on the excited-state intramolecular proton transfer (ESIPT), have been studied by fluorescence spectroscopy. It was found that at physiological pH, EYPC leads to the increase of the quantum yield of Tautomer fluorescence for HFs with multiple −OH groups. There is a temperature-dependent difference in the ESIPT process which takes place in HFs/EYPC systems. The findings are relevant for in vivo and in vitro studies of the oxidative stress process which involves cell membranes, where HFs are used as sensitive fluorescence probes.