Optical resolution of asymmetric triacylglycerols by chiral-phase high-performance liquid chromatography

Abstract

A simple method for direct optical resolution of some asymmetric triacylglycerols (TGs) has been established. The method employs chiral-phase high-performance liquid chromatography (HPLC). An enantiomeric pair of TGs comprising 1-eicosapentaenoyl-2,3-dicapryroyl- sn-glycerol (ECC) and 1,2-dicapryroyl-3-eicosapentaenoyl- sn-glycerol (CCE) was resolved on a CHIRALCEL OF™ or on a CHIRALCEL OD™ column. The separation of another pair of asymmetric TGs, 1-docosahexaenoyl-2,3-dicapryroyl- sn-glycerol (DCC) and 1,2-dicapryroyl-3-docosahexaenoyl- sn-glycerol (CCD), was achieved with the CHIRALCEL OD column. The chiral-phase HPLC method in combination with silver-ion HPLC and high-temperature gas chromatography was used for monitoring two interesterification reactions, whose products were chiral TGs. Interesterification of tricapryloylglycerol with ethyleicosapentaenoate or with ethyldocosahexaenoate was performed using Rhizomucor miehei lipase as the catalyst. The products targeted were the asymmetric pair of TGs, ECC and CCE or DCC and CCD. The amounts of sn-1-substituted products (ECC or DCC) were greater than their sn-3-substituted counterparts (CCE or CCD) throughout the reaction period, suggesting that R. miehei lipase had a stereopreference towards the sn-1 position over the sn-3 position.