Antioxidant Properties of Methionine Esters

Abstract

DURING feeding experiments we have found that 0.5 percent methionine in a semisynthetic diet containing 12 per cent cod liver oil prevents yellow discoloration of the diet and also the destruction of vitamins A and E (refs. 1–3). We have also studied the antioxidant properties of methionine and some derivatives using simple manometric techniques⁴ and have recorded the near infrared spectrum of CCl₄ extracts of the semisynthetic diet. The spectrophotometric data showed a relatively constant peak at 2.34µ and a variable peak at 2.88µ which increased as oxidation progressed, permitting use of the ratio of absorptions at these two wavelengths as an additional measure of oxidation. Using both criteria hydrochlorides of the methyl and ethyl esters of methionine showed unique properties. In contrast to other compounds which were tested there were rapid but relatively small initial changes followed by extended periods in which only very slow changes took place. The esters therefore seemed to be transformed to antioxidant compounds acting in a similar way to butylated hydroxy toluene (BHT).