DETERMINATION OF THE ENANTIOMERIC COMPOSITION OF 1,2-DIACYLGLYCEROLS FROM OLIVE OIL BY GC AND C-13-NMR SPECTROSCOPY

This paper reports a simple procedure to isolate 1,2-diacylglycerols f rom olive oil samples and outlines two analytical methods to evaluate their enantiomeric purity using C-13-NMR spectroscopy and gas chromato graphy. Isolation was achieved directly by flash chromatography. The f ree hydroxyl group of the diacylglycerols was acylated with enantiomer ically pure -alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chlorid e (MTPA-Cl) and the two respective diastereomers obtained were quantit atively analyzed by C-13-NMR. This procedure is suitable for both puri fied and crude samples. 1,2-Diacylglycerols were also transformed into 1,2-isopropylidene-3-MTPA-sn- and 1-MTPA-2,3-isopropylidene-sn-glycer ol in order to evaluate their original enantiomeric composition by gas chromatography. The optical purity of 1,2-sn-diacylglycerols was high er in a sample of oil from freshly harvested olives (70% enantiomeric excess) than in commercial virgin olive oils (50-55% enantiomeric exce ss).