The antioxidant action of N-acetylcysteine: Its reaction with hydrogen peroxide, hydroxyl radical, superoxide, and hypochlorous acid

N-acetylcysteine has been widely used as an antioxidant in vivo and in vitro. Its reaction with four oxidant species has therefore been examined. N-acetylcysteine is a powerful scavenger of hypochlorous acid (HOCl); low concentrations are able to protect α 1-antiproteinase against inactivation by HOCl. N-acetylcysteine also reacts with hydroxyl radical with a rate constant of 1.36 × 10 10 M −1s −1, as determined by pulse radiolysis. It also reacts slowly with H 2O 2, but no reaction of N-acetylcysteine with superoxide (O 2 −) could be detected within the limits of our assay procedures.