The effect of some amino acids on the oxidation of linoleic acid and its methyl ester

Manometric studies of the effect of certain amino acids on oxidation (measured as oxygen consumption) of linoleic acid, as well as the methyl esters of linoleic acid and linolenic acid dispersed in water or phosphate buffers at pH 7 to pH 5 have shown that The amino acids tested (except cysteine) have a potential antioxidative effect. The antioxidative capacity of different amino acids may be rather different (it is especially pronounced in the case of histidine and tryptophane). Under suitable conditions extremely low amino acid concentrations may have rather strong effect. The antioxidative efficiency is less pronounced than in earlier experiments with linoleate at pH>7, and decreases with decreasing pH. There may be a tendency towards a prooxidative inversion with relatively high amino acid concentrations, or at low pH. The antioxidative effect is enhanced and a prooxidative effect may be lowered or inverted into an antioxidative one by an addition of phosphate, or an emulsifier like Tween. A strong inhibitory effect is obtained by combined addition of phosphate and emulsifier like Tween, together with the amino acid. The antioxidative tendency was stronger in the case of methyl linoleate than with linoleic acid, and was also stronger with methyl linoleate than with methyl linolenate.