Easy access of dihydrofluoresceins as advanced fluorescence turn-on probes for oxidative stress

A mild NABH4/I2 strategy was designed to easily reduce fluoresceins to dihydrofluorescein alcohols and acids. Dihydrofluorescein alcohols exhibited surprisingly enhanced reactivity for oxidative stress sensing in comparison with the acid forms, using horseradish peroxidase/H2O2 as a model system for the generation of reactive radical species. Finally, two dual functional probes were then synthesized using our optimized reduction method, which showed great potentials for fluorescent imaging of subcellular oxidative stresses. [Display omitted] •A mild NaBH4/I2 based reduction method has been developed for the syntheses of dihydrofluoresceins.•Using this method is able to easily obtain both alcohol and acid forms of dihydrofluorescein in controllable ways.•The research shows the first evidence that dihydrofluorescein alcohols are much advanced substrates than the corresponding acids for HRP/H2O2 system.•Two dual functional probes have been prepared by NaBH4/I2 reduction for subcellular imaging of oxidative stresses.