Comparison of Oxidative Stability of Monogalactosyl Diacylglycerol, Digalactosyl Diacylglycerol, and Triacylglycerol Containing Polyunsaturated Fatty Acids

Abstract

Oxidative stability of three different lipid classes, namely, monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) from spinach and edible brown seaweed (Akamoku) and triacylglycerol (TAG) of linseed oil was compared. Analysis of oxygen consumption and polyunsaturated fatty acid (PUFA) composition demonstrated that spinach DGDG had the highest oxidative stability, followed by Akamoku DGDG, Akamoku MGDG, spinach MGDG, and linseed TAG. These results disagree with the order of oxidative stability expected from the average number of bis-allylic positions of each lipid. Additionally, DGDG constituents of both spinach and Akamoku showed higher oxidative stability than their MGDG constituents. The unusual oxidative stability of MGDG and DGDG could be conferred by the protection of bis-allylic positions of the PUFA against oxidative attack by the galactosyl moiety of the GL.