Positional distribution of Δ5-olefinic acids in triacylglycerols from conifer seed oils: General and specific enrichment in the sn-3 position |
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Authors: | Robert L Wolff Eric Dareville Jean-Charles Martin |
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Affiliation: | (1) INRA, Unité de Nutrition Lipidique, Dijon, France;(2) ISTAB, Laboratoire de Lipochimie Alimentaire, Université Bordeaux 1, Allée des Facultés, 33405 Talence cedex, France |
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Abstract: | Triacylglycerols (TAG) were purified from the storage lipids extracted from the seeds of several conifer species (Taxus baccata, Larix decidua, Sciadopytis verticillata, and Juniperus communis), each species belonging to one of the four families Taxaceae, Pinaceae, Taxodiaceae, and Cupressaceae, respectively. Each
species was characterized by a high content of 5,9-18:2, 5,9,12-18:3, 5,11,14-20:3, or 5,11,14,17-20:4 acids, respectively.
TAG were partially deacylated with ethylmagnesium bromide, and the resulting 1,2-, 2,3-diacylglycerols (DAG), and 2-monoacylglycerols
(MAG) were purified by thin-layer chromatography. 1,2- and 2,3-DAG were further fractionated by chiral column high-performance
liquid chromatography of the 3,5-dinitrophenylurethane derivatives. Alternately, TAG were subjected to porcine pancreatic
lipase, and the resulting 2-MAG were purified for further analysis. Gas-liquid chromatography of fatty acid methyl esters
prepared from the separated DAG and MAG, coupled with appropriate calculations, indicated that the Δ5-olefinic acids, irrespective
of the species, chainlengths and number of ethylenic bonds, were considerably enriched in the sn-3 position of TAG where they accounted for ca. 35 to 74 mole% of fatty acids esterified to this position (depending on the initial level of total Δ5-olefinic acids in TAG),
which corresponded to 79–94% of Δ5-olefinic acids esterified to the three positions. On the other hand, Δ5-olefinic acids
were less than 10% in the sn-2 position and less than 6% in the sn-1 position of TAG. This specific enrichment of Δ5-olefinic acids in the sn-3 position thus appears to be a general characteristic of conifer seed TAG. These results were extended to TAG from the seeds
of two pine species (Pinus koraiensis and P. pinaster) that are rich in Δ5-olefinic acids and available commercially on a ton-scale. |
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Keywords: | Chiral column high-performance liquid chromatography conifer seeds Cupressaceae Δ 5-olefinic acids 3 5-dinitrophenylurethane derivatives Grignard reagent pancreatic lipase Pinaceae positional distribution Taxaceae |
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