ARS | Publication request: Influence of fatty acid desaturation on spontaneous acyl migration in 2-monoacylglycerols

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 2012
Publication Date: November 20, 2012
Citation: Compton, D.L., Laszlo, J.A., Appell, M.D., Vermillion, K., Evans, K.O. 2012. Influence of fatty acid desaturation on spontaneous acyl migration in 2-monoacylglycerols. Journal of the American Oil Chemists' Society. 89(12):2259-2267.

Interpretive Summary: This research details efforts to uniquely monitor product purity during the eco-friendly production of chemical intermediates made from vegetable oils. Our mission is to develop new, value added uses for commodity crops and crop oils by developing bio-based chemicals and products that replace those made from petroleum. Much of today’s health and nutritional research investigates how the body uses and processes fats from food. This research has led to the development of naturally-derived synthetic fats, for example synthetic fats that mimic human milk fat. The manufacturing of these biomimetic fats depends on a particularly unstable intermediate called a 2-monoacylglycerol (2-MAG). Our research shows how an established analytical technique uniquely applied to making 2-MAG provides a superior method for monitoring the purity of 2-MAG. This demonstrated application of a new analytical method will be of use to other scientists and researchers trying to design new, healthier, and more nutritious synthetic fats.

Technical Abstract: The effect of desaturation from the C9 to the C15 carbon of 2-monoacylglycerol (2-MAG) fatty acids on spontaneous acyl migration is described. Density functional calculations for 2-monooleoylglycerol (C18:cis-delta9), 2-monolinoleoylglycerol (C18:cis-delta9,12), and 2-monolinolenoylglycerol (C18:cis-delta9,12,15) were performed using the B3LYP functional at the 6-31+G* basis set. Resultant theoretical activation energies, deltaG‡298.15, were determined to be 36.28, 35.65, and 37.18 kJ mol-**1, respectively. The three 2-MAG species were synthesized by lipase-catalyzed ethanolysis of their respective triacylglycerols and isolated in > 60% yield and at 2-MAG purities of > 95% relative to 1-monoacylglycerol (1-MAG). **1H NMR spectroscopy was used to monitor the spontaneous acyl migration of the 2-MAG species over a temperature range of 20 to 80°C. The relative energies of activation calculated from the Arrhenius relationships of the 2-MAG acyl migration rate constants were 73.3, 68.0, and 72.9 kJ mol-**1 for 2-monooleoylglycerol, 2-monolinoleoylglycerol, and 2-monolinolenoylglycerol, respectively. The kinetically determined relative activation energies were ~ 2-fold higher than the theoretical activation energies. In general, increasing desaturation after the C9 carbon of 2-MAG fatty acids had no appreciable effect on acyl migration rates.