THE TRIACYLGLYCEROL STRUCTURE OF OLIVE OIL DETERMINED BY SILVER ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY IN COMBINATION WITH STEREOSPECIFIC ANALYSIS

The compositions of positions sn-1, sn-2 and sn-3 of triacylglycerols from "extra-virgin" olive oil (Olea europaea) were determined. The procedure involved preparation of diacyl-rac-glycerols by partial hydrolysis with ethyl magnesium bromide; 1,3, 1,2- and 2,3-diacyl-sn-glycerols as (S)-(+)-1-(1-naphthyl)ethyl urethanes were isolated by high-performance liquid chromatography (HPLC) on silica, and their fatty acid compositions were determined. The same procedure was also carried out on the five main triacylglycerol fractions of olive oil after separation according to the degree of unsaturation by HPLC in the silver ion mode. Although stereospecific analysis of the intact triacyl-sn-glycerols indicated that the compositions of positions sn-1 and sn-3 were similar, the analyses of the molecular species demonstrated marked asymmetry. The data indicate that the "1-random, 2-random, 3-random" distribution theory is not always applicable to vegetable oils.