Acyl Migration Kinetics of Vegetable Oil 1,2-Diacylglycerols

摘要

The acyl migration kinetics of long-chain 1,2-diacylglycerol (1,2-DAG) to form 1,3-diacylglycerol (1,3-DAG) over the temperature range of 25-80 pC were examined using p#H-NMR spectroscopy. Lipase-catalyzed ethanolysis of high-oleic sunflower oil, followed by a series of solvent extraction steps, generated high purity 1,2-DAG (0.93 mol fraction of the DAG content). The 1,2-DAG mole fraction of 0.32 at equilibrium was found to be insensitive to temperature, indicating that long-chain acyl group migration is neither endothermic nor exothermic. Determination of the temperature-dependent, first-order reaction kinetic parameters revealed a 1,2-DAG half life (t /) of 3,425 h and 15.8 h at 25 and 80 pC, respectively. A comparison of 1,2-DAG with 2-monoacylglycerol indicated that there is no difference between the two in the potential energy state (G [double dagger]) of their respective transitions states or cyclic intermediates.