Fatty Acids with Conjugated Unsaturation - Lipid Library
Fatty Acids with Conjugated Unsaturation - Lipid Library
Fatty Acids with Conjugated Unsaturation - Lipid Library
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13 C-NMR spectroscopy of fatty acids <strong>with</strong> conjugated unsaturation<br />
13 C-NMR SPECTROSCOPY OF FATTY ACIDS AND DERIVATIVES<br />
<strong>Fatty</strong> <strong>Acids</strong> <strong>with</strong> <strong>Conjugated</strong> <strong>Unsaturation</strong><br />
<strong>Conjugated</strong> dienes<br />
The conjugated dienes attracting most attention are the so-called conjugated linoleic acids (CLA).<br />
These occur at low levels in the meat and milk fats of ruminant animals where they are produced<br />
by enzymic modification of linoleic acid in the rumen. They may also be produced by 9desaturation<br />
of octadec-11-enoic acid. These acids show important physiological effects and are<br />
reported to inhibit tumour growth. Alkali-isomerization of linoleic acid also gives a mixture of 9c11t<br />
and 10t12c dienes <strong>with</strong> some other isomers as minor components.<br />
By whatever method CLA is produced, it is usually a complex mixture of positional isomers and of<br />
stereoisomers, and full analysis requires gas chromatography, silver ion chromatography, and<br />
mass spectrometry of appropriate derivatives. 13 C-NMR has also been used to identify these<br />
mixtures and appropriate compounds have had to be synthesised or isolated. The best results are<br />
given by Lie Ken Jie et al. for all the 9,11 diene isomers and by Davis et al. for selected 8,10-,<br />
9,11-, 10,12- and 11,13-isomers. Chemical shifts are given in Tables 1 and 2.<br />
Table 1. Chemical shifts (ppm) for the four isomeric<br />
9,11-18:2 acids (Lie Ken Jie et al.).<br />
9c11t 9t11c 9t11t 9c11c<br />
1 174.32 174.34 174.22 174.27<br />
2 34.10 34.10 34.09 34.10<br />
3 24.95 24.95 24.98 24.97<br />
4 29.06 28.97 29.04 29.14<br />
5 - - - -<br />
6 - - - -<br />
7 - - - -<br />
8 27.66 32.06 32.61 27.46<br />
9 129.89 134.51 132.16 a 131.87 c<br />
10 128.71 125.72 130.37 b<br />
11 125.58 128.57 130.51 b<br />
123.58 d<br />
123.72 d<br />
12 134.76 130.17 132.43 a 132.14 c<br />
13 32.92 27.72 32.68 27.54<br />
14 29.41 29.73 29.40 29.68<br />
15 28.95 28.97 28.97 29.04<br />
16 31.77 31.77 31.82 31.81<br />
17 22.65 22.65 22.68 22.69<br />
18 14.12 14.12 14.13 14.13<br />
abcd : these pairs may be interchanged<br />
F.D. Gunstone © lipidlibrary.aocs.org 1<br />
.
13 C-NMR spectroscopy of fatty acids <strong>with</strong> conjugated unsaturation<br />
Table 2. Chemical shifts (ppm) for isomeric 18:2 methyl esters (Davis et al.).<br />
9c11c 9t11t 9c11t 11c13t 8t10c 10t12c<br />
1 179.98 179.86 180.09 180.09 180.05 180.09<br />
2 34.06 34.00 34.05 34.06 34.03 34.06<br />
3 24.68 24.67 24.67 24.69 24.63 24.67<br />
4 - - 29.03 - - 29.06<br />
5 - - 29.12 - - -<br />
6 - - 29.03 - - -<br />
7 29.57 29.36* 29.66 - 32.78 -<br />
8 27.52 32.56 27.65 - 124.32 29.39<br />
9 131.87 132.21 129.89 29.73 125.83 32.87<br />
10 123.72 130.46 128.73 27.69 128.54 134.58<br />
11 123.55 130.30 125.58 130.04 130.27 125.70<br />
12 132.19 132.53 134.80 128.66 27.71 128.60<br />
13 27.43 32.63 32.90 125.65 29.76 130.16<br />
14 29.64 29.42* 29.40 134.66 - 27.68<br />
15 - - 28.93 32.57 - 29.44<br />
16 31.76 31.77 31.76 31.59 31.87 31.50<br />
17 22.64 22.63 22.63 22.29 22.68 22.57<br />
18 14.09 14.10 14.10 13.95 14.12 14.06<br />
* these pairs may be interchanged<br />
F.D. Gunstone © lipidlibrary.aocs.org 2
13 C-NMR spectroscopy of fatty acids <strong>with</strong> conjugated unsaturation<br />
Enynes<br />
Reports are available for the chemical shifts for all carbon atoms in trans-octadec-11-en-9-ynoic<br />
acid and esters (also known as ximenynic or santalbic acid) and other acids/esters containing<br />
conjugated enyne systems (Table 3).<br />
Table 3. Chemical shifts for acids/esters containing conjugated enyne systems.<br />
(a) 9a11c-18:2* 9a11t-18:2*<br />
Methyl Glycerol<br />
(α)<br />
Glycerol<br />
(β)<br />
Methyl Glycerol<br />
(α)<br />
Glycerol<br />
(β)<br />
1 174.32 174.27 173.179 172.771 174.31 173.142 172.774<br />
2 34.10 34.074 33.997 34.142 34.074 33.974 34.138<br />
3 24.85 24.917 24.806 24.840 24.921 24.806 24.837<br />
4 28.81# 29.062 29.016 28.973 29.030 28.978 28.936<br />
5 28.88# 28.893 28.874 28.814 28.842<br />
6 30.07 28.817 28.805 28.783 28.710<br />
7 142.96 28.691 28.691 28.786 28.786<br />
8 109.50 19.542 19.500 19.500 19.329 19.324 19.324<br />
9 92.66 94.277 94.224 94.193 88.547 88.444 88.418<br />
10 84.90 77.561 77.482 77.489 79.287 79.304 79.319<br />
11 109.76 109.30 109.300 109.300 107.76 109.826 109.826<br />
12 144.58 142.67 142.618 142.602 143.45 143.296 143.306<br />
13 33.26 30.040 30.031 30.031 32.980 32.998 32.998<br />
14 28.72# 28.817 28.817 28.814 28.814<br />
15 28.56# 28.691 28.691 28.710 28.710<br />
16 31.74 31.706 31.701 31.701 31.690 31.697 31.697<br />
17 22.67 22.645 22.636 22.636 22.614 22.617 22.617<br />
18 14.16 14.119 14.130 14.130 14.103 13.103 13.103<br />
* all chemical shifts are given to three decimal places – those <strong>with</strong> 6 digits are reduced to 5 in<br />
this Table (Lie Ken Jie et al.).<br />
# these shifts may be interchanged.<br />
(a) heisteric acid 7c9a 11t-18:3 (Spitzer et al.).<br />
<strong>Conjugated</strong> trienes and tetraenes<br />
The common natural acids of this type are C18 compounds <strong>with</strong> triene unsaturation at the 9,11,13<br />
or 8,10,12 positions, and a 9,11,13,15-tetraene. These acids occur in several stereochemical<br />
forms. Chemical shifts for these compounds are listed in Table 4. Stellaheptaenoic acid<br />
(4c7c9t11t13t16c19c-22:7), isolated from a marine alga, contains the same conjugated tetra-ene<br />
unit as α-parinaric acid.<br />
Newer results for α- and β-eleostearic, punicic, and catalpic acids, collected in Table 5, differ from<br />
the older data in Table 3. The newer information is obtained from oils containing these acids and<br />
chemical shifts are given for both α and β chains. However, there is poor agreement between<br />
these two sets of data. This is illustrated for α-eleostearic acid in Table 6 where olefinic signals<br />
and assignments are compared.<br />
F.D. Gunstone © lipidlibrary.aocs.org 3
13 C-NMR spectroscopy of fatty acids <strong>with</strong> conjugated unsaturation<br />
Table 4. Chemical shifts (ppm) for natural acids <strong>with</strong> conjugated triene (Gunstone) and<br />
tetra-ene (Spitzer) systems [trivial names punicic (a), α-eleostearic (β), catalpic (c), βeleostearic(d),<br />
jacaric (e), calendic (f), α-parinaric (g), stellaheptaenoic (h].<br />
∆-9,11,13 ∆-8,10,12 ∆-9,11, ∆-4,7,9,11,13,<br />
13,15 16,19<br />
c t c c t t t t c t t t c t c t t c c t t c c c t t c c c<br />
Trivial a b c d e f g h<br />
5 Nc nc nc nc 28.89 28.85 nc 128.98<br />
6 Nc nc nc nc nc nc nc 26.61<br />
7 Nc nc nc nc 27.81 32.78 nc 128.69<br />
8 27.89 27.83 32.84 32.80 127.81# 126.21# 27.97 128.49<br />
9 128.96 128.95 126.12# 130.73 128.07# 128.71# 132.83 127.33<br />
10 132.38 132.91 128.79# 130.81 128.86# 130.85# 128.24 133.84<br />
11 127.87 125.98 130.82# 134.19 129.07# 132.04# 128.14 133.86<br />
12 128.02 134.90 131.75# 133.98 132.09# 132.71# 132.88 128.52<br />
13 132.62 131.52 132.77# 130.95 132.57# 134.66# 132.91 129.19<br />
14 128.86 130.73 134.70# 130.60 27.89 27.89 128.21 132.18<br />
15 27.65 32.53 27.58 32.53 nc nc 128.89 26.61<br />
16 31.94 31.58 31.95 31.58 31.57 31.56 134.52 130.37<br />
17 22.39 22.28 22.38 22.28 22.62 22.62 21.33 129.51<br />
18 14.02 13.95 14.00 13.95 14.10 14.11 14.37 26.61*<br />
# these olefinic signals have not been assigned and are listed in increasing numerical order.<br />
* also signals for C2 (33.94), C3 (23.09), C4 (128.54), C19 (129.50), C20 (130.41), C21 (20.89), C22<br />
(14.44).<br />
Table 5. Chemical shifts (ppm) for natural acids <strong>with</strong> conjugated triene<br />
systems (Blaise et al.).<br />
A/α A/β B/α B/β C/α C/β<br />
9 131.724 131.685 134.184 134.142 128.937 128.920<br />
10 128.837 128.818 130.631 130.613 132.426<br />
11 125.986 125.965 130.798 130.782 127.858 127.840<br />
12 132.926 132.906 130.963 130.942 128.025<br />
13 130.640 130.631 130.505 132.688 132.668<br />
14 135.164 135.141 134.444 134.426 - -<br />
α-eleostearic (A), β-eleostearic (B), punicic (C).<br />
Also, catalpic glycerol esters 134.897 (α), 132.760 (α),131,973 (β),131,957 (α), 128,715 (α and β),<br />
126.148 (β), 126.132 (α), 130.755 (β), 130.741 (α) – these chemical shifts are not assigned to<br />
individual carbon atoms and it is not clear why 9 values are listed.<br />
F.D. Gunstone © lipidlibrary.aocs.org 4
13 C-NMR spectroscopy of fatty acids <strong>with</strong> conjugated unsaturation<br />
Table 6. Chemical shifts (ppm) listed in increasing<br />
numerical value for olefinic carbon atoms in αeleostearic<br />
acid according to Tulloch and Blaise.<br />
Tulloch<br />
et al. (1979)<br />
Shift (ppm) Carbon<br />
atom<br />
Blaise<br />
et al. (1997)<br />
Shift (ppm) Carbon<br />
atom<br />
125.98 11 125.99 11<br />
128.95 9 128.84 10<br />
130.73 14 130.64 13<br />
131.52 13 131.72 9<br />
132.91 10 132.93 12<br />
134.90 12 135.16 14<br />
References<br />
o Blaise, P., Wolff, R. and Farines, M. Etude regiospecific de triacyglycerols d’huiles vegetales par clivage<br />
chimique et RMN 13 C haute resolution. Oleagineux Corps gras <strong>Lipid</strong>es, 4, 135-141 (1997).<br />
o Davis, A.L., McNeill, G.P. and Caswell, D.C. Analysis of conjugated linoleic acid isomers by 13 C-NMR<br />
spectroscopy. Chem. Phys. <strong>Lipid</strong>s, 97, 155-165 (1999).<br />
o Gunstone, F.D. High resolution 13 C-NMR spectroscopy of lipids. In: Advances in <strong>Lipid</strong> Methodology –<br />
Two, pp. 1-68 (ed. W.W. Christie, Oily Press, Dundee) (1993).<br />
o Lie Ken Jie, M.S.F. Pasha, M.K. and Ahmad, F. Ultrasound-assisted synthesis of santalbic acid and a<br />
study of triacylglycerol species in Santalum album (Linn.) seed oil. <strong>Lipid</strong>s, 31, 1083-1089 (1996).<br />
o Lie Ken Jie, M.S.F. Pasha, M.K. and Ahmad, F. Synthesis and nuclear magnetic resonance properties<br />
of all geometrical isomers of conjugated linoleic acids. <strong>Lipid</strong>s, 32, 1041-1044 (1997).<br />
o Mikhailova, M.V., Bemis, D.L., Wise, M.L., Gerwick, W.H., Norris, J.N. and Jacobs, R.S. Structure and<br />
biosynthesis of novel conjugated polyene fatty acids from the marine green alga Anadyomene stellate.<br />
<strong>Lipid</strong>s, 30, 583-89 (1995).<br />
o Spitzer, V., Tomberg, W. and Zucolotto, M. Identification of α-parinaric acid in the seed oil of Sebastiana<br />
brasiliensis Sprengel (Euphorbiaceae). J. Am. Oil Chem. Soc., 73, 569-573 (1996).<br />
o Spitzer, V., Tomberg, W. Hartmann, R. and Aichholz, R. Analysis of the seed oil of Heisteria silvanii<br />
(Olacaceae) – a rich source of a novel C18 acetylenic fatty acid. <strong>Lipid</strong>s, 32, 1189-1200 (1997).<br />
o Tulloch, A.P. and Bergter, L. Analysis of the conjugated triene acid containing oil from Fevillea trilobata<br />
by 13 C nuclear magnetic resonance spectroscopy. <strong>Lipid</strong>s, 14, 996-1002 (1979).<br />
Frank D. Gunstone<br />
James Hutton Institute (and Mylnefield <strong>Lipid</strong> Analysis), Invergowrie, Dundee (DD2<br />
5DA), Scotland<br />
Last updated: January 22 nd , 2007<br />
F.D. Gunstone © lipidlibrary.aocs.org 5