Abstract
Among nineteen amino acids examined, tyrosine, methionine and tryptophan showed antioxidative activity on linoleic acid in aqueous system at pH 7.0 and 9.0, but at pH 5.0, all amino acids showed no remarkable inhibition of oxidation of linoleic acid.
After incubation of amino acids together with linoleic acid for 6 days, in three amino acids; (tyrosine, methionine and tryptophan, ) two spots were detected on a paper-chromatogram respectively. In case of methioine, one spot was methionine and other was methionine-sulfoxide which is considered to be formed from methionine by oxidative action of peroxide or radical formed during autoxidation of linoleic acid and its oxidative reaction velocity is more rapid in alkaline solution than in acidic one. Antioxidative activity of methionine on linoleic acid became stronger along With the increase of concentration of methionine from 0.1, to 1.5×1.0-2 mol.
Although methionine-sulfoxide and methionine-sulfone had no influence on the stability of linoleic acid at 0.5×10-2 mol. respectively, but both compounds showed antioxidative activity in 0.3×10-2 mol. and pro-oxidative effect on linoleic acid in 1.0, 1.5×10-2 mol.
