Geometry of conjugated double bonds of CLA isomers in a commercial mixture and in their hepatic 20:4 metabolites.
Rats were fed a fat-free diet for 2 wk. After this period, while maintaining the animals on the same diet, the rats were given intragastrically 180 mg per day of a mixture of conjugated linoleic acids (CLA) as triacylglycerols. Gas chromatography mass spectrometry (GC-MS) analyses of this mixture, as well as hydrazine reduction and GC-MS and GC-Fourier transform infrared analyses of the resulting monoenes, revealed the presence of two major isomers, the 9c,11t- and the 10t,12c-18:2 accompanied by smaller amounts of the 8t, 10c and the 11c, 13t-18:2 isomers. Minor quantities of cis,cis and trans,trans conjugated isomers also were detected. The total fatty acid methyl esters from the liver lipids were fractionated by reversed-phase high-performance liquid chromatography, and the fraction containing the 20:4 isomers was further fractionated by silver nitrate thin-layer chromatography. A band containing two 20:4 conjugated isomers was submitted to hydrazine reduction and the resulting monoenes analyzed by GC-MS as dimethyl-oxazoline derivatives. The two conjugated isomers were tentatively identified as 5c,8c, 11c, 13t-20:4 and 5c,8c,12t,14c-20:4. These could be formed by desaturation and elongation of the 9c,11t- and 10t,12c-18:2 present in the commercial CLA mixture.
Sébédio
J L
JL
INRA, Unité de Nutrition Lipidique, Dijon, France. sebedio@inra.dijon.fr
Juanéda
P
P
Grégoire
S
S
Chardigny
J M
JM
Martin
J C
JC
Ginies
C
C
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004032:Diet; D005227:Fatty Acids / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D006834:Hydrazines; D007536:Isomerism; D008041:Linoleic Acids / Q000737:chemistry*; D008099:Liver / Q000378:metabolism*; D051381:Rats; D017550:Spectroscopy, Fourier Transform Infrared; D014280:Triglycerides / Q000378:metabolism
D005227:Fatty Acids; D006834:Hydrazines; D008041:Linoleic Acids; D014280:Triglycerides; C029424:hydrazine