Arachidonic acid autoxidation in an aqueous media effect of α‐tocopherol, cysteine and nucleic acids

The autoxidation of arachidonic acid dispersed in aqueous media was evaluated simultaneously with and without different agents, e.g., α‐tocopherol at different concentrations, cysteine, DNA and RNA. The autoxidation rate of arachidonic acid was evaluated by quantitative gas liquid chromatography (GLC) determination of the unoxidized acid and by spectrophotometric measurement of conjugated dienes. α‐Tocopherol exhibited a prooxidant activity at concentrations of 1.25 × 10−4 M and 1.25 × 10−5 M and a weak antioxidant activity at a concentration of 1.25 × 10−6 M. Cysteine showed antioxidant activity and greatly reduced the prooxidant activity of α‐tocopherol. DNA and RNA had no effect in either case. α‐Tocopherol oxidation was followed by high pressure liquid chromatography (HPLC). The prooxidant effect was accompanied by a rapid oxidation of α‐tocopherol, except in the presence of cysteine, which prevented the oxidation of α‐tocopherol.