Table 1: Oxidant species and antioxidant defense.

Oxidant species

Reactive oxygen species (ROS)Superoxide anion ()
Peroxide ()
Hydrogen peroxide (H2O2)
Hydroxyl radical ()
Hydroxyl ion ()

Reactive nitrogen species (RNS)Nitric oxide ()
Peroxynitrite ()
Nitrogen dioxide ()
Dinitrogen trioxide (N2O3)
Nitrosoperoxycarbonate ()

ROS resourcesMitochondrial electron transition
Enzyme reactions: peroxisomal oxidases, cytochrome P-450, NAD(P)H oxidases, and xanthine oxidase
Xenobiotics, drugs, and radiation: cisplatin, doxorubicin, and so forth.

RNS resourcesNitric oxide () from nitric oxide synthase 2 (NOS2)
Other RNS from reaction of nitric oxide () with superoxide anion () and other reactive species.

Antioxidant defense

Nonenzymatic antioxidantsGlutathione (GSH)
Coenzyme Q (CoQ)
Uric acid

Enzymatic antioxidantsSuperoxide dismutase (SOD)
Catalase (CAT)
Peroxiredoxin (Prx)
Glutathione reductase (GR)
Glutathione peroxidases (GPx)
Glutathione-S-transferases (GST)
Thioredoxin and thioredoxin reductase

Natural (food) antioxidantsVitamin A/C/E