Theoretical study on oxidation mechanism of fluorescent probe, coumarin-7-pinacolboronate by various reactive oxygen species

Hydrogen peroxide (H₂O₂) as relatively stable reactive oxygen species gains considerable attention because it can regulate physiological and pathological processes. In order to better detect H₂O₂, fluorescent probes were widely applied. Over the past 20 years, a great deal of boronate-based fluorescent molecular probes appeared due to relatively simple oxidation reaction. However, the reaction mechanisms that boronate derivatives were converted into fluorescent product by H₂O₂ are poorly studied. In this paper, taking coumarin-7-pinacolboronate (CBU) as an example, the oxidation mechanism of boronate-based probes by various reactive oxygen species was studied by theoretical calculations. The results found that (1) the chemical reaction mechanisms are nearly identical for the reactions of CBU with hydrogen peroxide, hypochlorous acid, peroxynitrite, and tyrosine hydroperoxide, respectively. (2) There is not radical intermediate during the reaction. (3) The different reactive oxygen species has a strong influence on rate limiting step and reaction rate.