N-2-(2-Ethoxycarbonyl-propyl) α-Phenylnitrone: An Efficacious Lipophilic Spin Trap for Superoxide Detection

The spin trap N-2-(2-ethoxycarbonyl-propyl) α-phenylnitrone, EPPN 1, synthesized by methods previously described, has been purified by recrystallization. A measure of its octanol–phosphate buffer partition coefficient (Poct = 29.8) indicated that EPPN was quite lipophilic, yet it could be easily solubilized in water up to 60 mmol L−1. Although this nitrone was unsuitable for detecting hydroxyl radical, it efficiently trapped several carbon-centered radicals as well as superoxide in aqueous media, without yielding any artifactual signals. Kinetic studies of the superoxide adduct decay gave rate constants kD of 2 × 10−3 and 2.1 × 10−3 s−1 at pH 5.6 and pH 7, respectively. EPPN can be considered as an easily prepared and highly pure spin trap, allowing efficient detection of superoxide in aqueous environments.