Inhibitors of the prooxidant activity of α‐tocopherol

The prooxidant activity of α ‐tocopherol ( α ‐T) can be reduced or inverted into antioxidant activity by various compounds. An important antioxidant activity was obtained by the association of α ‐T with cysteine, BHT, hydro‐quinone and ascorbyl palmitate. EDTA 10 ‐4 M, phos‐phoric, malonic and citric acids can partially decrease the prooxidant effect of α ‐T, although the strong acids exhibited no antioxidant activity without α ‐T. Other amino acids such as glycine and alanine do little to reduce the prooxidant behavior of α‐T while they showed a strong antioxidant activity without α‐T. The distribution of hydroperoxide isomers of linoleic acid formed with and without α ‐T was not modified by the addition of the various compounds except BHT, which led to the production of only 13 c,t and 9 c,t isomers as observed with α ‐T. The oxidation of α ‐T in the presence of linoleic acid was completely inhibited by the addition of cysteine, phosphoric, malonic and citric acids, BHT, hydro‐quinone, ascorbyl palmitate and EDTA 10 ‐4 M. The inhibitors of the prooxidant activity of α ‐T could act in two different ways: by chelating the prooxidant metals traces (i.e., amino acids, EDTA) and/or by regenerating α ‐T, thus reducing the concentration of chromanoxy radical which would be involved in the prooxidant activity (i.e. phosphoric, malonic, citric acids, cysteine and the common antioxidants).