A High-Resolution NMR Approach Combined to MALDI-TOF-MS to Estimate the Positional Distribution of Acyl-Linked Unsaturated Fatty Acids in Triacylglycerols

Triacylglycerols (TAGs) are the most abundant constituents of vegetable oils and adipose tissues. TAG analysis is even, nowadays, challenging because the presence of three (often different) fatty acyl residues leads to many different, regioisomeric species. While the overall fatty acyl composition of TAG can be determined by gas chromatography/mass spectrometry (GC/MS), all positional information is completely lost by this approach. Therefore, GC/MS is often replaced or combined with LC/MS that provides information (by MS/MS) which fatty acyl residues are present in a given TAG and sometimes also about the location at the glycerol backbone. Since TAGs are normally available in huge amounts, the comparably low sensitivity of NMR is not a major issue. We show that high-resolution C-13 NMR spectroscopy is an excellent method to determine the overall fatty acyl composition and the positions of the related (unsaturated) fatty acyl residues in a given TAG molecule. These data will be compared with MALDI-TOF MS data of the same vegetable oil samples. Although the C-13 NMR method is particularly applicable to unsaturated TAG, this approach can be regarded as a significant methodological progress in this field.