Linoleic acid oxidation catalyzed by various amino acids and cupric ions in freeze‐dried model systems

The present investigation into the effect of amino acids on linoleic acid oxidation in freeze‐dried model system illustrates the existence of an autocatalytic chain reaction, in which all amino acids, except cysteine, exhibited minor antioxidant behavior. The antioxidant effect might be attributed to the absence of protonated amino nitrogen. Linoleic acid alone had an induction period of 15 hr, and on the addition of various α‐amino acids, the systems had induction periods ranging from 16‐19 hr. This increase did not exhibit any specific function for the studied amino acids. Cysteine exhibited an exceptional prooxidant effect due to the role of the HS‐group. The addition of copper at concentrations of 10‐5M and 10‐3M to the model systems composed of linoleic acid and various a‐amino acids exhibited minor and highly prooxidant effects, respectively, The prooxidant effect of these amino acids in the presence of copper might be due to amino acids‐copper complexes.