Reaction of endogenous Coenzyme Q(10) with nitrogen monoxide and its metabolite nitrogen dioxide

Objectives: Coenzyme Q(10), incorporated in DOPC lyposomes or naturally present in liver bovine mitochondria or in human blood plasma, was reacted with nitrogen dioxide (•)NO(2) or with a (•)NO/(•)NO(2) mixture. Methods and Results: The reaction course was monitored by Electron Paramagnetic Resonance (EPR) spectroscopy and in all cases the formation of a di-tert-alkyl nitroxide was observed, deriving from the addition of (•)NO(2) to one of the double bonds, most likely the terminal one, of the isoprenic chain. The rate constant for nitroxide formation was also determined by EPR spectroscopy and an initial rate of ca. 7 × 10(−8 )M s(−1) was obtained.