GC-MS and GC-FID of seven seed oils containing conjugated fatty acids

Authors: Goldschmidt, Robert; Byrdwell, W Craig

Submitted to: Journal of Chromatographic Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2021
Publication Date: 4/15/2021
Citation: Goldschmidt, R.J., Byrdwell, W.C. 2021. GC-MS and GC-FID of seven seed oils containing conjugated fatty acids. Journal of Chromatographic Science. 43:259–273.. https://doi.org/10.3390/separations8040051.
DOI: https://doi.org/10.3390/separations8040051

Interpretive Summary: The detailed fatty acid compositions of seven seed oils known to contain high levels of conjugated fatty acids were determined. Conjugated fatty acids contain two or more carbon-carbon double bonds separated by one carbon-carbon single bond. In comparison to their non-conjugated counterparts, they exhibit differences in their physical, chemical, and biological properties, and they are purported to have health benefits, including anti-carcinogenic effects. The major fatty acids of these oils have been previously reported, but this work presents the distributions in detail, including isomer distributions. In addition to the major conjugated fatty acid components, all seven oils contained small amounts of additional conjugated fatty acids, most of which were octadecatrienoic (18:3) acid isomers. Two oils also contained small amounts of conjugated octadecadienoic (18:2) acids. One oil, known to contain four isomers of conjugated octadecatetraenoic (18:4) acid, showed evidence of a possible fifth such isomer.

Technical Abstract: The fatty acid compositions, including isomer compositions, of seven seed oils containing conjugated fatty acids (CFA) were determined. Seed oils were extracted using a modified Folch extraction, converted to fatty acid methyl esters, and analyzed by gas chromatography (GC) with mass spectrometry (MS) and flame ionization detection (FID). The MS detector was operated in positive-ion chemical ionization mode using methane reagent gas. GC was performed using two columns providing different retention characteristics: a poly(ethylene glycol) column and a more polar biscyanopropyl column. The complimentary information provided by the two columns was crucial in peak identification in several cases. The major CFA species in the samples are well known, but all contained lesser amounts of additional CFA that have not been widely reported. All samples contained multiple species of conjugated linolenic acid, and two samples also contained small amounts of conjugated linoleic acid. The seed oils of Jacaranda mimosifolia and Calendula officinalis were found to contain 8c,10t,12t-18:3, the natural occurrence of which has only been recently reported in some other samples. The seed oil of Impatiens balsamina has been reported to contain four conjugated 18:4 species, but there is evidence for a possible fifth conjugated 18:4 isomer.