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TitleChemical synthesis and gas chromatographic behaviour of γ-stearidonic (18:4n-6) acid
Publication TypeJournal Article
Year of Publication2015
AuthorsVyssotski, M., Lagutin K., MacKenzie A., and Itabashi Y.
JournalJAOCS, Journal of the American Oil Chemists' Society
Pagination383 - 391
Date Published2015
ISSN0003021X (ISSN)
Keywordsalgae, biology, Esterification, Esters, Fatty Acids, gas chromatography, GC, GC-MS, Ionic liquids, nuclear magnetic resonance, nuclear magnetic resonance spectroscopy, Octadecapentaenoic, Octadecatetraenoic, Stearidonic, Tolypothrix
Abstractγ-Stearidonic acid, 18:4n-6, a potential product of β-oxidation of arachidonic acid (20:4n-6), was only recently positively identified in a living organism - a thermophilic cyanobacterium Tolypothrix sp., albeit at low levels, whilst some indirect evidence suggests its wider presence, e.g. in a unicellular marine alga. We have prepared 18:4n-6 using an iodolactonisation chain-shortening approach from 22:5n-6 and obtained its 1H-, 13C-, COSY- and HSQC NMR spectra, with 18:5n-3 spectra also recorded for a comparison. The GC and GC-MS behaviour of its methyl ester was also studied. Like another Δ3 polyunsaturated acid, octadecapentaenoic (18:5n-3), 18:4n-6 rapidly yields 2-trans isomer upon formation of dimethyloxazoline derivative. On a polar ionic liquid phase (SLB-IL100, 200°C) the methyl ester could be mistaken for 18:3n-3, while on methylsilicone phase (BP1, 210°C) it eluted ahead of 18:3n-6 and 18:4n-3, suggesting that when present it may be easily misidentified during GC analysis of fatty acids. © AOCS 2015.

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