Triacylglycerols of the olive fruit (Olea europaea L.) : characterization of mesocarp and seed triacylglycerols in different cultivars by liquid chromatography and 13C NMR spectroscopy

Abstract

Triacylglycerols of mesocarp and seed oils extracted from olive fruits of different cultivars were characterized. The analysis of the profiles of the triglyceride isomers which were determined by HPLC, evidenced that ECN 48 (OOO-OOP) and ECN 46 (OLO) triglycerides were the major components of mesocarp and seed oils, whereas triglycerides acylated with the linoleoyl chain appeared to be more abundant in seed oil, i.e. LLL (ECN 42), OLL-PLL (ECN 44), and POL-OLO (ECN 46). Mesocarp and seed oils, likewise the cultivars differed significantly (P<0.05) with regard to all the triglyceride components. 13 C NMR spectroscopy based on carbonyl carbon resonances of triglyceride acyl chains was applied to carry out the regiospecific analysis of triacylglycerols. Acyl chain composition, chain distribution among 1(3)- and 2-glycerol positions, and chain 2-positional specificity, were determined. The results confirmed that two different pools of fatty acids esterified at 1(3)- and 2-positions in triacylglycerols of mesocarp and seed oils exist, the saturated chains being by almost 100% at 1(3)-positions. 2-positional specificity evidenced that the oleoyl chain moved away from a pure random model less than the linoleoyl chain. 2-Distribution and 2-specificity data of oleoyl and linoleoyl chains along with linoleoyl 1(3)-distribution values, appeared to discriminate significantly (P<0.05) mesocarp and seed oils, but no cultivar discrimination was achieved. The effect of fatty acid concentration on their distribution between triacylglycerol positions and the low variability of 2-positonal specificity values of unsaturated chains over a wide range of vegetable oils were highlighted.