EFFECT OF LINOLEIC-ACID POSITION IN TRIACYLGLYCEROLS ON THEIR OXIDATIVE STABILITY

Four synthetically produced triacylglycerols containing linoleic and p almitic acid in different known positions were used to determine the e ffect of fatty acid position on their relative rates of autoxidation. The triacylglycerols were sn-1,3-dipalmitoyl-sn-2-linoleoyl (PLP); sn- 1,2(2,3)-dipalmitoyl-sn-1(3)-monolinoleoyl (PPL); sn 2-palmitoyl-sn-1, 3-dilinoleoyl (LPL); and sn 1 (3)-palmitoyl-sn-1,2(2,3)-dilinoleoyl (P LL) glycerols. Oxidation was evaluated both by peroxide value, and rev ersed phase HPLC with ultraviolet absorbance detection at 235 nm for c onjugated diene of triacylglycerol's oxidized linoleic acid. Triacylgl ycerols were oxidized at 60 degrees C in the dark. PLL had lower oxida tive stability than LPL. This effect may be due to easier interactions between adjacent linoleic acid of PLL compared to nonadjacent linolei c acid of LPL during autoxidation. PLP had lower oxidative stability t han PPL. Reversed phase HPLC analysis showed that at a low oxidation l evel, PLP and PPL produced monohydroperoxide and LPL and PLL produced both mono- and bishydroperoxides. These results are further evidence t hat fatty acid position on triacylglycerols plays a role in lipid oxid ation.