Geometrical and positional isomers of unsaturated furan fatty acids in food

Furan fatty acids (FuFA) are important antioxidants found in low concentrations in many types of food. In addition to conventional FuFA which normally feature saturated carboxyalkyl and alkyl chains, a few previous studies indicated the FuFA co-occurrence of low shares of unsaturated furan fatty acids (uFuFA). For their detailed analysis, the potential uFuFA were enriched by centrifugal partition chromatography (CPC) or countercurrent chromatography (CCC) followed by silver ion chromatography from a 4,7,10,13,16,19-docosahexaenoic acid ethyl ester oil, a 5,8,11,14,17-eicosapentaenoic acid ethyl ester oil and a latex glove extract. Subsequent gas chromatography with mass spectrometry (GC/MS) analysis enabled the detection of 16 individual uFuFA isomers with a double bond in conjugation with the central furan moiety. In either case, four instead of two uFuFA isomers previously reported in food, respectively, were detected by GC/MS. These isomers showed characteristic elution and abundance patterns in GC/MS chromatograms which indicated the presence of two pairs of cis/trans-isomers (geometrical isomers).