The synthesis of homogeneous triglycerides of eicosapentaenoic acid and docosahexaenoic acid by lipase

Abstract

A highly efficient synthesis of homogeneous triglycerides of either pure eicosapentaenoic acid, 1, or docosahexaenoic acid, 2, by an immobilized non-regiospecific yeast lipase from Candida antarctica is described. Two methods were used: Interesterification of tributyrin and direct esterification of glycerol with stoichiometric amount of 99 % EPA or DHA as ethyl esters and free fatty acids, respectively. Both processes were performed under vacuum at 65°C in the absence of any solvent. The volatile co-products were condensed into a cooled trap, thus shifting the equilibrium toward completion. Complete incorporation was reached in less than 72 h for all cases, but the direct esterification was found to proceed considerably faster than the transesterification as were both processes involving EPA as compared to DHA. High-field 1H NMR spectroscopy analysis offered detailed investigation of the intermediate glycerides during the direct esterification reaction. The purity of the resulting crude products which were afforded in excellent yields was very high.