The application of flavonoid derivatives as redox-responsive fluorescent probes in hydrophobic microenvironment

Recently, the study of redox chemistry especially the detection of redox species (such as GSH and H2O2) in biological systems becomes particularly significant, as oxidative stress has been widely believed to play essential roles in health and disease. In this context, we designed and synthesized two series of flavonoid derivatives with different electron effect substituents NHCOCH3 (1) or NH2 (2), and tested their fluorescence characteristics in BSA, which was rich in alpha-helix structures and could form hydrophobic microenvironment. The results showed that 1 performed as a ratiometric ESIPT (excited-state intramolecular proton transfer) fluorescent probe while 2 tended to be a “Turn-on” probe. After modifying both of them with H2O2-reactive boronated-based benzyl group, or thiol-promoted specific OS cleavage group 2,4-dinitrobenzenesulfonyl (DNBS), respectively, we obtained 3, which could be used for H2O2 detection as a ratiometric ESIPT probe in BSA solution, and 6, which could image endogenous GSH as a “Turn-on” fluorescent sensor in Hela cells.