“…In vitro, melatonin scavenges hydroxyl radicals, peroxides, singlet oxygen and nitric oxide Tan et al, 2002), and it has been shown that melatonin is superior to vitamin E as a peroxyl radical scavenger (Pieri et al, 1994). Compared with other major antioxidants (ascorbate and vitamin E), melatonin is also 60-and 70-fold more effective, respectively, in reducing oxidative DNA damage (assessed as the production of 8-hydroxy-29-deoxyguanosine) (Qi et al, 2000). Second, melatonin has an indirect effect on the antioxidant machinery by stimulating antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, and other antioxidant molecules, such as ascorbate, trolox and NADH (Gitto et al, 2001), but also by inhibiting pro-oxidant enzymes such as nitric oxide synthase and lipoxygenase Anisimov, 2003;Rodriguez et al, 2004).…”