Can Free Radicals Be Good for You?(Current Commentary) (Report‪)‬

Free radicals--the bad guys It is widely held (1) that free radicals are involved in the initiation and propagation of many and various illnesses, including cancer, heart disease, stroke, rheumatoid arthritis, diabetes, and multiple sclerosis (MS). The list runs on, and even the process of ageing itself is believed to be driven by free radicals, also called reactive oxygen species (ROS) or reactive oxygen intermediates (ROI). Now, the species classified as ROS or ROI are derived from molecular oxygen ([O.sub.2]) which obviously we need to breathe to stay alive. In the main, ROS are the superoxide radical anion ([O.sup.-*.sub.2]), its conjugate acid, the hydroperoxyl radical (HO[O.sup.*]), the hydroxyl radical (H[O.sup.*]), organic peroxyl radicals (RO[O.sup.*]), alkoxyl radicals (R[O.sup.*]) as bona fide free radical (unpaired electron) molecules, but also included on the list are molecular (especially, singlet) oxygen ([O.sub.2]), organic hydroperoxides, ROOH and hydrogen peroxide itself, [H.sub.2][O.sub.2]. It can be said that all oxygen free radicals are ROS/ROI but not all ROS/ROI are free radicals. As respired [O.sub.2] enters living cells it is metabolised e.g. by the mitochondria to [O.sup.-*.sub.2], which is not in itself strongly oxidising, but it provides a source of other ROS. To avoid living cells being overwhelmed by [O.sup.-*.sub.2], they contain the enzyme superoxide dismutase which catalyses the reaction [equation (I)]: