Identification of triacylglycerols containing two short-chain fatty acids at sn-2 and sn-3 positions from bovine udder by fast atom bombardment tandem mass spectrometry

Several triacylglycerol (TAG) molecular species, that contain two short-cha in fatty acids (C4 to C8) at the sn-2 and sn-3 positions of the glycerol ba ckbone, were isolated from bovine udder by using solvent extraction and sil ica gel column chromatography, Their structures were identified by fast ato m bombardment (FAB) tandem mass spectrometry (MS/MS), based on the informat ion obtained from collision-induced dissociation (CID) spectra of sodium-ad ducted molecules ([M + Na](+)) of model TAG compounds which had been synthe sized from glycerol and appropriate fatty acids. For each species, the rela tive positions of the three fatty acids on the glycerol backbone, as well a s fatty acid composition and double-bond position in the Fatty acyl group, were determined. A majority of sodium-adducted molecules observed in the FA B mass spectrum were mixtures of at least two components that have differen t fatty acid composition but the same molecular mass. In addition, all the components present in mixtures of all the species contain a long-chain fatt y acid (C12 to C18) at the sn-1 position, a short-chain fatty acid (C4 to C 8) at the sn-2 position, and a butyric acid uniquely at the sn-3 position. Copyright. (C) 2000 John Wiley & Sons, Ltd.