Superoxide radical trapping and spin adduct decay of 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BocMPO): kinetics and theoretical analysis

Spin-trapping of oxygen-centered radicals such as superoxide radical is increasingly becoming important in the study of biological oxidations. Superoxide spin-trapping and decay kinetics in aqueous media of the new solid nitrone 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BocMPO) are reported and compared to those of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO). Superoxide spin-trapping by BocMPO is significantly slower than that by DEPMPO and DMPO, and the half-life of BocMPO-superoxide adduct is shorter than that of DEPMPO-superoxide adduct. The BocMPO spin-trapping ability and stability of its superoxide adducts are rationalized based on theoretical calculations.