Docosahexaenoic Acid is More Stable to Oxidation when Located at the <i>sn</i>‐2 Position of Triacylglycerol Compared to <i>sn</i>‐1(3)

Abstract

Abstract Regio‐isomeric effects on the oxidative stability of triacylglycerols (TAG) containing docosahexaenoic acid (DHA) were investigated using two pairs of regio‐isomerically pure TAG, namely 1,3‐dihexadecanoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PDP)/1,2‐dihexadecanoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PPD) and 1,3‐dioctadecenoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (ODO)/1,2‐dioctadecenoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (OOD) where P, O, and D represent palmitic acid, oleic acid, and DHA respectively. Each pair of regio‐isomers was subjected to accelerated auto‐oxidation (at 40 or 50 °C inside a dark oven). In each case, the TAG oxidized more slowly when DHA was located at the sn ‐2 position (PDP and ODO) compared to the sn ‐1(3) position (PPD and OOD), as evidenced by slower development of peroxide value, slower depletion of DHA, and slower generation of secondary oxidation products propanal and trans , trans ‐2,4‐heptadienal. The positional effect on auto‐oxidation was more pronounced when DHA occurred in combination with oleic acid than with palmitic acid.