AO/AOE Location/activity Discovery Key function(s) References
SOD Epididymis 1968   important enzyme Fridovich [212];
GPX Tissues 1957 Destroys H2O2 and organic hydroperoxides by catalysing reduction of hydroperoxides Mills [213].
CAT Peroxisomes 1900 Antioxidant enzyme against hydrogen peroxide Loew [214]; Fujii et al. [193];
Vitamin C Mammalian tissues and plasma. Water soluble. Isolated in 1928 Body metabolism, antioxidant electron donor Burns [215]; Cheeseman et al. [216]; Bendich [141]
Vitamin E Mammalian tissues and plasma. Lipid-soluble 75 years ago Chain-breaking antioxidant; Evans and Bishop [125]; Burton et al. [126]; Ingold et al. [127]; Cheeseman et al. [216]
Carotenoids (e.g. β-carotene) Pro-vitamin A 1929 Singlet oxygen quenchers and as antioxidants Olson [217]
Selenium In vivo micronutrient required for GPx  first confirmed in 1933, identified in lab animals, 1957 Antioxidant, required for proper functioning of GPx. Spallholz [218];   Shor-Posner et al. [182].
Vitamin A Plasma 1913 Immune function Olson [217]
Lycopene Body tissues, testis   potent antioxidant  
N-acetylcysteine (NAC) In vivo in plasma some
50 years ago
Its effect is based on breaking of the disulphide bridges of the high-molecular-weight glycoproteins
of the mucus, resulting in reduced viscosity. Replenishes intracellular GSH levels
Aitio [92]; Atkuri et al. [167].
Key: SOD is Superoxide dismutase: GPx is Glutathione peroxidase: CAT is Catalase; AO/AOE is antioxidant/antioxidant enzyme
Table 3: Summary of antioxidants and key function(s).