Ascorbic acid and ascorbyl palmitate have only minor effect on the formation and decomposition of methyl linoleate hydroperoxides

Effects of ascorbic acid (AA) and ascorbyl palmitate (AP) on lipid hydroper oxides were evaluated during the formation and decomposition of methyl lino leate hydroperoxides (ML-OOH). AA and AP at 1 and 10 mM levels had no effec t on the formation of ML-OOH during the autoxidation of methyl linoleate at 40 degreesC. However, depending on the reaction medium, AA and AP at 0.2 a nd 2 mM either slightly inhibited or accelerated the decomposition of 40 mM cis,trans ML-OOH in hexadecane or in hexadecane-in-water emulsion. The inc reased decomposition rate of ML-OOH, when compared to a control sample, was apparently due to the reductive activity of AA and AP on metal ions presen t in the system, as the addition of EDTA improved the stability of ML-OOH. The more detailed analysis of the decomposition reactions of ML-OOH suggest s that under favorable reaction conditions AA and AP were, to some extent, capable of acting as hydrogen atom donors to peroxyl radicals and reducers of hydroperoxides to more stable hydroxy compounds. However, since all thes e effects of AA and AP on lipid hydroperoxides were relatively small, it is assumed that the antioxidative activity of AA and AP as well as their effe ct on the stability and reactions of lipid hydroperoxides in biological sys tems and in foods is mainly related to their synergistic interactions with other antioxidative compounds such as tocopherols.