Kinetic Evaluation of Spin Trapping Rate Constants of New CYPMPO-type Spin Traps for Superoxide and Other Free Radicals

CYPMPO (5-(2,2-dimethyl-1,3-propoxyl cyclophosphoryl)-5-methyl-1-pyrroline N-oxide) is a phosphorus containing spin trap that has been useful in aqueous media. Using a kinetic ESR spin trapping technique, we evaluated free radical trapping rate constants of two newly synthesized CYPMPO-type spin traps, including 2,2-dibutyl-substituted CYPMPO (DBCYP) and 5-phenyl-substituted CYPMPO (PhCYP). We investigated the spin trapping of five free radical species, i.e., superoxide, hydroxyl radical, alkoxyl radical, alkyl peroxyl radical and methyl radical. Other than superoxide, spin trapping rate constants of DBCYP and PhCYP are comparable to CYPMPO, ranging from 43.9% to 101% of CYPMPO's corresponding rate constants. However, PhCYP's spin-trapping rate constant against superoxide was 44% higher than that of CYPMPO. The results indicate that DBCYP and PhCYP may be the spin traps as useful as CYPMPO either in aqueous or non-aqueous medium.