On the use of 1,3-diphenylisobenzofuran (DPBF). Reactions with carbon and oxygen centered radicals in model and natural systems

1,3-diphenylisobenzofuran (DPBF) is a fluorescent molecule which possesses a highly specific reactivity towards singlet oxygen (1O2) forming an endoperoxide which decomposes to give 1,2-dibenzoylbenzene. This reaction between DPBF and 1O2 can be followed by measuring the decrease in fluorescence intensity of DPBF. In order to check the specificity of DPBF toward free radicals a series of experiments was carried out in Triton-X micelles and in natural systems (rat liver microsomes), in which DPBF was reacted with hydroxy (HO•), alkyloxy (RO•), alkylperoxy (ROO•), and C-centered radicals (2-cyanoisopropyl radical). In all cases, the DPBF is rapidly transformed to 1,2-dibenzoylbenzene in the case of O-centered radicals and to the corresponding adduct in the case of 2-cyanoisopropyl radical. The experiments in the model systems were also carried out from the chemical point of view and the reaction products were isolated and identified. From the results obtained, it should be stressed that DPBF must be used with caution in complex biological systems for the detection of 1O2, as it also reacts with different radical species.