ARS | Publication request: Identification of the unsaturated heptadecyl fatty acids in the seed oils of Thespesia populnea and Gossypium hirsutum

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 5, 2012
Publication Date: September 1, 2012
Citation: Dowd, M.K. 2012. Identification of the unsaturated heptadecyl fatty acids in the seed oils of Thespesia populnea and Gossypium hirsutum. Journal of the American Oil Chemists' Society. 89(9):1599-1609.

Interpretive Summary: Fatty acid composition was determined for the seed oils of Thespesia populnea (Seaside Mahoe) and cottonseed variety SG-747. Unusual 17-carbon fatty acids were found in both oils, but were in much higher concentrations in the Thespesia seed. The identity of these acids was determined by a series of chemical modifications combined with gas chromatography and mass spectrometry. The acids identified appear to be products of alpha-oxidation, a secondary degradation process that is not fully understood in plants. The work will increase our knowledge of the oil composition of cottonseed and related plant species and sheds some light on the biochemical processes that are occurring in these species. The work should be interest to researchers trying to modify the fatty acid composition of cottonseed oil to improve its marketability.

Technical Abstract: The fatty acid composition of the seed oils of Thespesia populnea and cotton variety SG-747 (Gossypium hirsutum) were studied to identity their 17-carbon fatty acids. With a combination of chemical derivatization, gas chromatography, and mass spectrometry, 8-heptadecenoic acid, 9-heptadecenoic acid, and 8,11-heptadecadienoic acids were identified in both oils. Additionally, traces of 10-heptadecenoic acid were identified in the T. populnea oil. Although these odd-carbon number fatty acids are present in only minor amounts in cottonseed oil, they make up about ~2% of the fatty acids in T. populnea seed oil. The identification of these acids indicates that fatty acid alpha-oxidation is not restricted to cyclopropene fatty acids in these plants, but also occurs with unsaturated fatty acids. Combined with malvalic acid (generally accepted as being formed by alpha-oxidation of sterculic acid), ~7% of the fatty acids in T. populnea seed have under gone alpha-oxidization. The results should help clarify the composition of T. populnea seed oil, which has been reported inconsistently in the literature.