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

It has recently been shown that high-resolution C-13 nuclear magnetic resonance (NMR) spectroscopy is a technique which can provide valuable information about the acyl distribution and acyl positional distribution (1,3-acyl and 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, previous assignments of C-13 NMR spectra are either tentative or incomplete. Thus, 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 concentration dependence of the shifts of all resonances. Thus, in Vegetable oils, the full assignment of C-13 resonances must be made by progressive addition 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 accurate analysis of the acyl positional distribution (1,3-acyl and 2-acyl) of glycerol tri-esters. From the knowledge of the acyl positional distribution (1,3-acyl and 2-acyl) of glycerol tri-esters interesting biochemical information can be achieved. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.