Antioxidant properties of phenols against superoxide radicals

摘要

The antioxidant properties of pyrocatechol, resorcinol, hydroquinone and pyrogallol against superoxide radicals were determined in a stepwise kinetic manner. The best and most stable antioxidant properties were recorded for pyrocatechol, followed by hydroquinone. Antioxidant and pro-oxidant properties were found for resorcinol and pyrogallol, especially at higher concentrations (greater than 50 μg/cm~3) and longer irradiation times (15 and 20 min). The positions of the hydroxy groups were crucial for antioxidant and pro-oxidant properties. Ortho and para were more effective in taking electrons from superoxide radicals than meta and vicinal phenols. However, phenols generally lose the electrons slowly and so are changed to pro-oxidants. This phenomenon could explain the leaking of electrons in the respiratory chain, formation of oxygen radicals in the mitochondria and the lower than theoretically possible production of adenosine triphosphate.