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United States Department of Agriculture

Agricultural Research Service

Research Project: Improvement and Utilization of Natural Rubber- and Castor Oil-producing Industrial Crops

Location: Bioproducts Research

Title: Ratios of regioisomers of minor acylglycerols less polar than triricinolein in castor oil estimated by mass spectrometry (Abstract))

item Lin, Jiann-tsyh

Submitted to: Abstract of Agronomy Meetings
Publication Type: Abstract only
Publication Acceptance Date: 3/17/2012
Publication Date: 9/30/2012
Citation: Lin, J.T. 2012. Ratios of regioisomers of minor acylglycerols less polar than triricinolein in castor oil estimated by mass spectrometry (Abstract). Abstract of Agronomy Meetings. 0.

Interpretive Summary: Castor oil has been used in industry such as the manufacture of biodegradable plastics, nylon, plasticizers, lubricants, cosmetics and paints. We have recently identified 34 molecular species of triacylglycerols containing three fatty acids including poly hydroxy fatty acids on a glycerol backbone in castor oil. Various isomers of the same molecular species of triacylglycerols with different fatty acids on the different locations on the glycerol backbone affect the physical property of the oil for industrial uses, such as viscosity, pour point and melting point. The ratios of the isomers of each molecular species of triacylglycerols were estimated. This will help to characterize the oil for industrial uses.

Technical Abstract: The ratios of regioisomers of triacylglycerols (TAG) have been estimated by mass spectrometry using the fact that the neutral loss of fatty acid (FA) from the sn-2 position is energetically less favored in comparison with that from sn-1,3 positions. However regioisomeric TAG standards were needed for making calibration curves and the estimation of the ratios of regioisomers were limited to the standards (AAB type TAG) available. No ABC type regioisomeric TAG standards are commercially available. Our method used here has no such limitations. Our method can be used for AAB and ABC types of TAG and AAAB type of tetraacylglycerols without the standards. Hydroxy FA has many industrial uses such as the manufacture of biodegradable lubricants, plastics, paints and cosmetics. Regiospecificity affects the physical property and the human absorption of TAG. We have recently reported the identification of new molecular species of acylglycerols containing hydroxy FA and TAG containing three normal FA less polar than triricinolein by electrospray ionization mass spectrometry of the lithium adducts in castor oil. We report here the ratios of regioisomers of these minor acylglycerols. The ratios of regioisomers of TAG (ABC and AAB types) and tetraacylglycerols (AAAB type) were estimated by the relative abundances of the fragment ions from the neutral losses of FA as a,ß-unsaturated FA at the sn-2 position. The ratios of the regioisomers estimated were of thirty four molecular species of TAG and tetraacylglycerols containing hydroxy FA and ten molecular species of TAG containing three normal FA. The order of the contents of regioisomers of TAG with the FA at the sn-2 position are: nonhydroxy FA > monohydroxy FA > dihydroxy FA > trihydroxy FA. For tetraacylglycerols (AAAB type) such as ricinoleoylricinoleoyl-ricinoleoyl-oleoyl-glycerol (RRRO), ricinoleoylricinoleoyl chain was predominately at the sn-2 position, while ricinoleate was not detected at the sn-2 position.

Last Modified: 8/24/2016
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