Location: Bioproducts ResearchTitle: Ratios of regioisomers of the molecular species of triacylglycerols in lesquerella (Physaria fendleri) oil estimated by mass spectrometry Author
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2015
Publication Date: 11/24/2016
Citation: Lin, J.T., Fagerquist, C.K., Chen, G.Q. 2016. Ratios of regioisomers of the molecular species of triacylglycerols in lesquerella (Physaria fendleri) oil estimated by mass spectrometry. Journal of the American Oil Chemists' Society. 93(2):183-191. doi: 10.1007/s11746-015-2769-2. Interpretive Summary: Ricinoleate, a hydroxy fatty acid in castor oil, has many industrial uses such as the manufacture of biodegradable and renewable plastics, plasticizers, lubricants, cosmetics, paints and surfactants. Fatty acids are stored as triacylglycerols in oil seeds. Lesquerolate, a homolog of ricinoleate, in lesquerella oil can be used for industry similar to those of ricinoleate. Lesquerella is a new industrial oilseed crop in the southwestern region of the U.S. valued for its lesquerolate. Lesquerella is desired to produce ricinoleate because castor contains toxic substances such as ricin. We identified and quantified 74 molecular species of triacylglycerols in lesquerella oil and estimated the ratios of the regioisomers of each one.
Technical Abstract: The ratios of regioisomers of 74 molecular species of triacylglycerols (TAG) in lesquerella oil were estimated using HPLC and the electrospray ionization mass spectrometry of the lithium adducts of TAG in the HPLC fractions of lequerella oil. The ratios of relative abundances of the fragment ions from the neutral losses of fatty acids (FA) as a-lactones at the sn-2 position (MS3) were used as the ratios of the regioisomers. The fragmentation mechanisms of prominent ions from the neutral losses of glycerol backbone were proposed. The decreasing order of the preference of FA incorporation at the sn-2 position of the regioisomers of the molecular species of TAG in lesquerella was as: normal FA > OH18 (monohydroxy FA with 18 carbon atoms) > diOH18 > OH20 > diOH20, while in castor was as: normal FA > OH18 > OH20 > diOH18 > triOH18. Unlike in castor, elongation (from C18 to C20) was more effective than hydroxylation in lesquerella to incorporate hydroxy FA at the sn-1/3 positions. The block of elongation in lesquerella may be used to increase the content of hydroxy FA, e.g., ricinoleate, at the sn-2 position of TAG and to produce triricinolein (or castor oil) for industrial uses. The content of normal FA at sn-2 position was about 95%, mainly oleate (38%), linolenate (31%) and linoleate (23%). The content of hydroxy FA at the sn-1/3 positions was 91% mainly lesquerolic acid (85%) and the content of normal FA was 6.7 %.