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Positional distribution of Δ5‐acids in triacylglycerols from conifer seeds as determined by partial chemical cleavage
Author(s) -
Blaise Pierre,
Tropini Veronique,
Farines Marie,
Wolff Robert L.
Publication year - 1997
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-997-0163-4
Subject(s) - pinaceae , pinus koraiensis , botany , chemistry , resin acid , fatty acid , cupressaceae , stereochemistry , organic chemistry , pinus <genus> , biology , pollen
The positional distribution of various Δ5‐acids in the seed triacylglycerols from several conifer species has been established after partial chemical degradation with Grignard reagent. The species studied were representative of four conifer families and were specially selected for their particularly high Δ5‐acid contents. These species were Taxus baccata (Taxaceae; 5,9‐18:2 acid, 11.9%), Larix decidua (Pinaceae; 5,9,12‐18:3 acid, 28.5%), Sciadopytis verticillata (Taxodiaceae; 5,11,14‐20:3 acid, 16.7%), and Juniperus communis (Cupressaceae; 5,11,14,17‐20:4 acid, 19.8%). Calculations from the fatty acid compositions of triacylglycerols and of the mixture of 1,2‐ and 2,3‐diacylglycerols generated by the Grignard reagent indicated that, for the four species, there was a considerable enrichment of Δ5‐acids (generally more than ten times) in the 1,3‐positions as compared to the 2‐position, where Δ5‐acids represented always less than 2% of total fatty acids esterified to triacylglycerols. This distribution was practically independent from the species (four families studied), the chainlength (18 or 20 carbon atoms), and the number of ethylenic bonds (two to four) in the Δ5‐acids. Similar distributions were established for triacylglycerols from the seeds of three pine species that are available on a ton‐scale: Pinus pinea, P. koraiensis , and P. pinaster . These observations confirm and extend previous studies conducted with other conifer species by similar techniques or by 13 C‐nuclear magnetic resonance spectroscopy. Consequently, the almost exclusive location of Δ5‐acids in the external positions of triacylglycerols is now well established and appears to be a general feature of conifer seed oils.