Curcumin was shown to be a potent scavenger of a variety of reactive oxygen species including hydroxyl radicals, nitrogen dioxide radicals, and superoxide radicals (Payton et al. 2007; Goel et al. 2008).
For example, the reaction between free radicals nitrogen oxide (NO) and superoxide (O2–) under physiological conditions can form strong oxidizing and nitrating intermediates such as peroxynitrite (ONO2−), which can nitrate tyrosine residues in proteins [ 3– 6].
Inflammatory disorders are characterized, among other events, by the production of significant amounts of free radicals, nitrogen reactive species, and cytokines such as TNF-α, IL-1β, and IL-6 [ 18].
Widely known free radicals of nitrogen species include nitric oxide radical (NO), peroxynitrite radical (ONOO−), nitroxyl anion HNO−, nitrosonium cation (NO+), higher oxides of nitrogen (N2O3, NO2), and S-nitrosothiols (RSNO) [ 25– 28].
They found that treatment of purified recombinant GTPase with superoxide anion radical or nitrogen dioxide radicals in vitro resulted in guanine nucleotide dissociation.
Additionally, NAC also reacts with hydroxyl radical (OH), nitrogen dioxide (NO2) and thiyl radicals to reduce oxidative stress [ 19].
Modification of LDL by 1-electron oxidants, such as tyrosyl radical or nitrogen dioxide radical, leads to the formation of lipid hydroperoxides and advanced products of oxidation, i.e. alkanes, aldehydes and isoprostanes.
Peroxynitrite (ONOO−), formed from the rapid reaction of NO with superoxide has also been shown to promote lipid peroxidation [ 38, 60, 61], probably due to the reactivity of decomposition products hydroxyl radical and nitrogen dioxide (NO2).
ROS include not only O2−, hydroxyl radicals, alkoxyl and peroxyl radicals, NO, and nitrogen dioxide radicals but also nonradical species such as hydrogen peroxide (H2O2), hypochlorite, peroxynitrite, singlet oxygen, lipid peroxides, and others.
In particular, it was found that the NO addition has a catalytic effect on the flame dynamics, since it participates in a reaction cycle leading to the consumption of active H, O, and OH radicals by nitrogen containing species and results in reduction of the laminar flame speeds even though the flame temperature is essentially unaffected.
