Article

Journal of the American Oil Chemists' Society

, Volume 75, Issue 12, pp 1749-1755

First online:

A simple method of preparation of methyl trans-10,cis-12- and cis-9,trans-11-octadecadienoates from methyl linoleate

  • O. BerdeauxAffiliated withINRA, Unité de Nutrition Lipidique Email author 
  • , L. VoinotAffiliated withINRA, Unité de Nutrition Lipidique
  • , E. AngioniAffiliated withINRA, Unité de Nutrition Lipidique
  • , P. JuanédaAffiliated withINRA, Unité de Nutrition Lipidique
  • , J. L. SébédioAffiliated withINRA, Unité de Nutrition Lipidique

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Abstract

Pure conjugated isomers of linoleic acid were prepared on a large scale by alkali-isomerization of purified methyl linoleate. The methyl esters of alkali-isomerized linoleic acid contained mainly the methyl cis-9,trans-11- and trans-10,cis-12-octadecadienoates (44 and 47%, respectively). These two isomers were then separated and purified by a series of low-temperature crystallizations from acetone. The isomeric purity obtained for the cis-9,trans-11-octadecadienoate isomer was >90% and that of the trans-10,cis-12-octadecadienoate isomer was 89 to 97%. The isolated yield of the two isomers corresponded to 18 and 25.7%, respectively, of the starting material. The structure of the two isomers was confirmed using partial hydrazine reduction, silver nitrate-thin-layer chromatography of the resulting monoenes and gas chromatography coupled with mass spectrometry of the 4,4-dimethyloxazoline derivatives. Fourier transform infrared spectroscopy of the monoenes gave the confirmation of the geometry of each double bond.

Key words

Conjugated linoleic acid (CLA) 4,4-dimethyloxazoline derivative GC-FTIR GC-MS hydrazine reduction isomerization linoleic acid low-temperature crystallization NMR silver nitrate-thin layer chromatography UV