SYNTHESIS OF METHYL 9c,11t-OCTADECADIENOATE
1015
8. Chin, S.F, J.M. Storkson, W. Liu, K.J. Albright, and M.W.
Pariza, Conjugated Linoleic Acid (9,11- and 10,12-Octadeca-
dienoic Acid) Is Produced in Conventional But Not Germ-Free
Rats Fed Linoleic Acid, J. Nutr. 124:694–701 (1994).
9. Cawood, P., D.G. Wickens, S.A. Iversen, J.M. Braganza, and
T.C. Dormandy, The Nature of Diene Conjugation in Human
Serum, Bile and Duodenal Juice, FEBS Lett. 59:280–283
(1983).
10. Banni, S., B.W. Day, R.W. Evans, F. Corongiu, and B. Lom-
bardi, Liquid Chromatographic-Mass Spectrometric Analysis of
Conjugated Diene Fatty Acids in a Partially Hydrogenated Fat,
J. Am. Oil Chem. Soc. 71:1321–1325 (1994).
Thus, urea complexation with 110 g of FAME and 110 g of
urea gave 87 g of a nonadduct fraction and 22 g of an adduct
fraction. GC analysis of the nonadduct fraction showed an in-
crease in the amount of 9c,11t-18:2 to 75%, with other com-
ponents as listed in Table 1, while the adduct fraction con-
tained only 38.4% 9c,11t-18:2. A second urea complexation
with 87 g of FAME and 87 g of urea gave 55 g of a nonadduct
fraction and 28 g of adduct fraction. GC analysis of the non-
adduct fraction showed that 9c,11t-18:2 comprised 83.0% of
the total (compared to 59% in the adduct).
11. Gunstone, F.D., and A.I. Said, Methyl 12-Mesyloxyoleate as a
Source of Cyclopropane Esters and of Conjugated Octadeca-
dienoates, Chem. Phys. Lipids 7:121–134 (1971).
12. Fay, L., and U. Richli, Localisation of Double Bond in Polyun-
saturated Fatty Acids by Gas Chromatography-Mass Spectrom-
etry After 4,4-Dimethyloxzoline Derivatisation, J. Chromatogr.
541:89–98 (1991).
13. Luthria, D.L., and H. Sprecher, 2-Alkenyl-4,4-Dimethyloxazo-
lines Derivatives for the Structural Elucidation of Isomeric Un-
saturated Fatty Acids, Lipids 28:561–564 (1993).
14. Zhang, J.Y., Q.T. Yu, B.N. Liu, and Z.H. Huang, Chemical
Modification in Mass Spectrometry IV. 2-Alkenyl-4,4-
Dimethyloxalines as Derivatives for the Double Bond Location
of Long-Chain Olefinic Acids, Biomed. Mass. Spectrom.
15:33–44 (1988).
In conclusion, the authors have developed a simple and
rapid method to prepare 9c,11t-18:2 from methyl ricinoleate
on a sufficient scale for nutritional experiments. The distribu-
tion of the 9c,11t isomers in this fraction (9c,11t-18:2, 83%;
9c,11c-18:2, 4.4%; and 9t,11t, 0.4%) is similar to what is usu-
ally found in dairy products (21). This fraction will be of great
interest to test the biological activity of such a mixture, con-
sidering that previous studies were effected on fractions that
did not reflect the isomeric composition found in dairy prod-
ucts.
ACKNOWLEDGMENT
15. Dobson, G., and W.W. Christie, Structural Analysis of Fatty
Acids by Mass Spectrometry of Picolinyl Esters and Dimethyl-
oxazoline Derivatives, Trends Anal. Chem. 15:130–137 (1996).
16. Bascetta, E., F.D. Gunstone, and C.M. Scrimgeour, Synthesis,
Characterisation, and Transformation of a Lipid Cyclic Perox-
ide, J. Chem. Soc. Perkin Trans. I:2199–2205 (1984).
17. Tassignon, P., P. de Waard, T. de Rijk, H. Tournois, D. de Wit,
and L. de Buyck, An Efficient Countercurrent Distribution
Method for the Large-Scale Isolation of Dimorphecolic Acid
Methyl Ester, Chem. Phys. Lipids 71:187–196 (1994).
18. Spitzer, V., F. Marx, and K. Pfeilsticker, Electron Impact Mass
Spectra of Some Conjugated Diene and Triene C18 Fatty Acids,
J. Am. Oil Chem. Soc. 71:873–876 (1994).
19. Young, D.C., and P. Vouros, Gas Chromatography–Mass Spec-
trometry of Conjugated Dienes by Derivatization with 4-
Methyl-1,2,4-Triazoline-3,5-Dione. J. Chromatogr. 522:
295–302 (1990).
20. Hopkins, C.Y., Fatty Acids with Conjugated Unsaturation, Top-
ics in Lipid Chemistry, edited by F.D. Gunstone, Elek Books,
London, 1972, Vol. 3, pp. 37–85.
This paper is published as part of a program funded by the Scottish
Office Agriculture, Environment and Fisheries Department.
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[Received November 12, 1996; accepted March 25, 1997]
JAOCS, Vol. 74, no. 8 (1997)