Formation of Superoxide Anion during Ferrous Ion-Induced Decomposition of Linoleic Acid Hydroperoxide under Aerobic Conditions

We studied the mechanism of formation of oxygen radicals during ferrous ion-induced decomposition of linoleic acid hydroperoxide using the spin trapping and chemiluminescence methods. The formation of the superoxide anion (O₂^.-) was verified in the present study. The hydroxyl radical is also generated through Fenton type decomposition of hydrogen peroxide produced on disproportionation of O₂^.-. A carbon-centered radical was detected using 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO) as a spin trap. Alkoxyl radical formation is essential for the conversion of linoleic acid hydroperoxide into the peroxyl radical by ferrous ion. It is likely that the alkoxyl radical [R₁CH(O^.)R₂] is converted into the hydroxylcarbon radical [R₁C^.(OH)R₂] in water, and that this carbon radical reacts with oxygen to give the α-hydroxyperoxyl radical [R₁R₂C(OH)OO^.], which decomposes into the carbocation [R₁C⁺(OH)R ₂] and O₂^.-.