The following are biological antioxidants which act against the free radicals formed inside the body, EXCEPT:
Selenium
Glycine
Uric acid
Ascorbic acid
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.