Synthesis of sn-2 docosahexaenoyl monoacylglycerol by mild enzymatic transesterification of docosahexaenoic acid ethyl ester and glycerol in a solvent-free system

The enzymatic transesterification of docosahexaenoic acid (DHA) ethyl ester with glycerol was performed with several lipases in a solvent-free system and it involves the initial formation of sn-2 docosahexaenyl monoacylglyceride. This DHA derivative is highly relevant for improving the bioavailability of DHA and it has received increasing interest in the field of nutrition. Three commercial lipases, from Rhizomucor miehei (RML), Alcaligenes sp (QL), and Candida antarctica-fraction B (CALB) were tested. In certain cases (CALB), using an excess of DHA ethyl ester and high temperatures the transesterification reaction continues to the formation of triacylglycerides, but in other cases, sn-2 monoacylglyceride (2-MG) is the unique synthetic product even in the presence of high concentrations of DHA ethyl ester. At low temperatures (e.g. 37°C), RML derivatives synthesize only 2-MG in 15 min. These very mild conditions are very interesting for the thermal oxidative stability of *Corresponding authors: Jose M. Guisan and Gloria Fernandez-Lorente, Instituto de Catálisis, CSIC. Campus UAMCSIC, 28049 Madrid, Spain; Instituto de Investigación en Ciencias de la Alimentación (CIAL), CSIC-UAM, 28049 Madrid, Spain E-mails: [email protected], [email protected]