Acyl positional distribution of glycerol tri-esters in vegetable oils: a C-13 NMR study

It has recently been shown that high-resolution C-13 nuclear magnetic reson ance (NMR) spectroscopy is a technique which can provide valuable informati on about the acyl distribution and acyl positional distribution (1,3-acyl a nd 2-acyl) of glycerol tri-esters of different vegetable oils. It has also been observed that many of the carbon atoms of alpha- and beta- acyl chains in tri-acyl-glycerol show different C-13 NMR chemical shifts. However, pre vious assignments of C-13 NMR spectra are either tentative or incomplete. T hus, through a series of INADEQUATE experiments, we made a full assignment of all C-13 resonances of glycerol tri-esters. We also noticed a strong con centration dependence of the shifts of all resonances. Thus, in Vegetable o ils, the full assignment of C-13 resonances must be made by progressive add ition of known glycerol tri-esters. Following this method, we report a full assignment of the C-13 spectra of seed and olive oils obtaining an accurat e analysis of the acyl positional distribution (1,3-acyl and 2-acyl) of gly cerol tri-esters. From the knowledge of the acyl positional distribution (1 ,3-acyl and 2-acyl) of glycerol tri-esters interesting biochemical informat ion can be achieved. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.