The following are biological antioxidants which act against the free radicals formed inside the body, EXCEPT:
The peroxides that are formed by radical damage to lipids in membranes and plasma lipoproteins are reduced to hydroxy fatty acids by glutathione peroxidase, a selenium-dependent enzyme (hence the impoance of adequate selenium intake to maximize antioxidant activity). Ascorbate, uric acid and a variety of polyphenols derived from plant foods act as water-soluble radical trapping antioxidants, forming relatively stable radicals that persist long enough to undergo reaction to non-radical products. Ubiquinone and carotenes similarly act as lipid-soluble radical-trapping antioxidants in membranes and plasma lipoproteins. Lipid peroxides are also reduced to fatty acids by reaction with vitamin E. Ref: Bender D.A. (2011). Chapter 45. Free Radicals and Antioxidant Nutrients. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Selenium
Glycine
Uric acid
Ascorbic acid