Antioxidant and Anti-Inflammatory Activities of Essential Oils: A Short Review

Miguel, Maria Graça

) which is quickly converted to hydrogen peroxide (H 2 O 2 ), spontaneously, or by the enzyme superoxide dismutase. Hydrogen peroxide can then also be reduced by transition metal ions generating the hydroxyl radical (HO • ), one of the strongest oxidizing agents that can rapidly react with polyunsaturated fatty acids, resulting the production of peroxyl radicals (ROO • ). Peroxide hydrogen can also oxidise halide ions (Cl -) to hypochlorous acid (HOCl), which is a strong oxidant that can react with amines producing chloramines, some of them being very toxic [18] [19] [20] [21] [22] . These radicals are commonly known as ROS (reactive oxygen species). Nevertheless and during an inflammatory process, there is also the generation of other free radicals named RNS (reactive nitrogen species). Nitric oxide ( • NO) and peroxynitrite anion (ONOO -) are two examples of this sort of radicals. Nitric oxide is produced in large quantities by the inducible nitric oxide synthases (iNOS) in activated macrophages and neutrophils during defence and immunological reactions. However this reactive species can also exerts its toxicity by generating the peroxynitrite anion after reacting with the superoxide anion radical [22, [23] [24] [25] .