Quantitative triacylglycerol analysis of whole vegetable seeds by1H and13C magic angle sample spinning NMR spectroscopy

High-resolution¹³C and¹H magic angle sample spinning nuclear magnetic resonance (NMR) spectra have been obtained and used to define the relative unsaturated acyl distribution of triacylglycerols in whole oil seeds. Inverse gated proton decoupled¹³C and¹H NMR spectra permit the quantitative analysis of seeds containing simple oils,e.g., sunflower seeds containing oleyl and linoleyl unsaturates only. More sensitive¹³C NMR techniques are necessary for the analysis of specific seed classes. One such class is the rapeseed, which is especially difficult due to its low oil content (≈ 2 mg oil/seed) and complex unsaturated acyl profile of oleyl, linoleyl, linolenyl, erucyl, and eicosenoyl. The Distortionless Enhancement by Polarization Transfer technique significantly improves sensitivity to the extent that single rapeseeds can be examined within an hour of acquisition time. Furthermore, some positional (1,3- or 2-glycerol attachment) groups can be identified leading to a partial estimation of the 1,3-, 2-acyl distribution.