Conjugated Dienes
The conjugated dienes attracting most attention are the so-called conjugated linoleic acids (CLA). These occur at low levels in the meat and milk fats of ruminant animals where they are produced by enzymic modification of linoleic acid in the rumen. They may also be produced by 9-desaturation of octadec-11-enoic acid. These acids show important physiological effects and are reported to inhibit tumour growth. Alkali-isomerization of linoleic acid also gives a mixture of 9c,11t and 10t,12c dienes with some other isomers as minor components. See our web page on the occurrence of conjugated fatty acids.
By whatever method CLA is produced, it is usually a complex mixture of positional isomers and of stereoisomers, and full analysis requires gas chromatography, silver ion chromatography, and mass spectrometry of appropriate derivatives. 13C-NMR has also been used to identify these mixtures and appropriate compounds have had to be synthesised or isolated. The best results are given by Lie Ken Jie et al. (1997) for all the 9,11 diene isomers and by Davis et al. (1999) for selected 8,10-, 9,11-, 10,12- and 11,13-isomers. Chemical shifts are given in Tables 1 and 2.
Table 1. Chemical shifts (ppm) for the four isomeric 9,11-18:2 acids (Lie Ken Jie et al., 1997) | ||||
9c,11t | 9t,11c | 9t,11t | 9c,11c | |
---|---|---|---|---|
1 | 174.32 | 174.34 | 174.22 | 174.27 |
2 | 34.10 | 34.10 | 34.09 | 34.10 |
3 | 24.95 | 24.95 | 24.98 | 24.97 |
4 | 29.06 | 28.97 | 29.04 | 29.14 |
5 | – | – | – | – |
6 | – | – | – | – |
8 | 27.66 | 32.06 | 32.61 | 27.46 |
9 | 129.89 | 134.51 | 132.16a | 131.87c |
10 | 128.71 | 125.72 | 130.37b | 123.58d |
11 | 125.58 | 128.57 | 130.51b | 123.72d |
12 | 134.76 | 130.17 | 132.43a | 132.14c |
13 | 32.92 | 27.72 | 32.68 | 27.54 |
14 | 29.41 | 29.73 | 29.40 | 29.68 |
15 | 28.95 | 28.97 | 28.97 | 29.04 |
16 | 31.77 | 31.77 | 31.82 | 31.81 |
17 | 22.65 | 22.65 | 22.68 | 22.69 |
18 | 14.12 | 14.12 | 14.13 | 14.13 |
abcd: These pairs may be interchanged. |
Table 2. Chemical shifts (ppm) for isomeric 18:2 methyl esters (Davis et al., 1999). | ||||||
9c,11c | 9t,11t | 9c,11t | 11c,13t | 8t,10c | 10t,12c | |
---|---|---|---|---|---|---|
1 | 179.98 | 179.86 | 180.09 | 180.09 | 180.05 | 180.09 |
2 | 34.06 | 34.00 | 34.05 | 34.06 | 34.03 | 34.06 |
3 | 24.68 | 24.67 | 24.67 | 24.69 | 24.63 | 24.67 |
4 | – | – | 29.03 | – | – | 29.06 |
5 | – | – | 29.12 | – | – | – |
6 | – | – | 29.03 | – | – | – |
7 | 29.57 | 29.36* | 29.66 | – | 32.78 | – |
8 | 27.52 | 32.56 | 27.65 | – | 124.32 | 29.39 |
9 | 131.87 | 132.21 | 129.89 | 29.73 | 125.83 | 32.87 |
10 | 123.72 | 130.46 | 128.73 | 27.69 | 128.54 | 134.58 |
11 | 123.55 | 130.30 | 125.58 | 130.04 | 130.27 | 125.70 |
12 | 132.19 | 132.53 | 134.80 | 128.66 | 27.71 | 128.60 |
13 | 27.43 | 32.63 | 32.90 | 125.65 | 29.76 | 130.16 |
14 | 29.64 | 29.42* | 29.40 | 134.66 | – | 27.68 |
16 | 31.76 | 31.77 | 31.76 | 31.59 | 31.87 | 31.50 |
17 | 22.64 | 22.63 | 22.63 | 22.29 | 22.68 | 22.57 |
18 | 14.09 | 14.10 | 14.10 | 13.95 | 14.12 | 14.06 |
Enynes
Reports are available for the chemical shifts for all carbon atoms in trans-octadec-11-en-9-ynoic acid and esters (also known as ximenynic or santalbic acid) and other acids/esters containing conjugated enyne systems (Table 3).
Table 3. Chemical shifts for acids/esters containing conjugated enyne systems | |||||||
(a) | 9a,11c-18:2* | 9a,11t-18:2* | |||||
---|---|---|---|---|---|---|---|
Methyl | Glycerol (α) | Glycerol (β) | Methyl | Glycerol (α) | Glycerol (β) | ||
1 | 174.32 | 174.27 | 173.179 | 172.771 | 174.31 | 173.142 | 172.774 |
2 | 34.10 | 34.074 | 33.997 | 34.142 | 34.074 | 33.974 | 34.138 |
3 | 24.85 | 24.917 | 24.806 | 24.840 | 24.921 | 24.806 | 24.837 |
4 | 28.81# | 29.062 | 29.016 | 28.973 | 29.030 | 28.978 | 28.936 |
5 | 28.88# | 28.893 | 28.874 | 28.814 | 28.842 | ||
6 | 30.07 | 28.817 | 28.805 | 28.783 | 28.710 | ||
7 | 142.96 | 28.691 | 28.691 | 28.786 | 28.786 | ||
8 | 109.50 | 19.542 | 19.500 | 19.500 | 19.329 | 19.324 | 19.324 |
9 | 92.66 | 94.277 | 94.224 | 94.193 | 88.547 | 88.444 | 88.418 |
10 | 84.90 | 77.561 | 77.482 | 77.489 | 79.287 | 79.304 | 79.319 |
11 | 109.76 | 109.30 | 109.300 | 109.300 | 107.76 | 109.826 | 109.826 |
12 | 144.58 | 142.67 | 142.618 | 142.602 | 143.45 | 143.296 | 143.306 |
13 | 33.26 | 30.040 | 30.031 | 30.031 | 32.980 | 32.998 | 32.998 |
14 | 28.72# | 28.817 | 28.817 | 28.814 | 28.814 | ||
15 | 28.56# | 28.691 | 28.691 | 28.710 | 28.710 | ||
16 | 31.74 | 31.706 | 31.701 | 31.701 | 31.690 | 31.697 | 31.697 |
17 | 22.67 | 22.645 | 22.636 | 22.636 | 22.614 | 22.617 | 22.617 |
18 | 14.16 | 14.119 | 14.130 | 14.130 | 14.103 | 13.103 | 13.103 |
(a) Heisteric acid 7c,9a,11t-18:3 (Spitzer et al., 1997). *All chemical shifts are given to three decimal places – those with 6 digits are reduced to 5 in this Table (Lie Ken Jie et al., 1997). #These shifts may be interchanged. |
Conjugated Trienes and Tetraenes
The common natural acids of this type are C18 compounds with triene unsaturation at the 9,11,13 or 8,10,12 positions, and a 9,11,13,15-tetraene. These acids occur in several stereochemical forms. Chemical shifts for these compounds are listed in Table 4. Stellaheptaenoic acid (4c,7c,9t,11t,13t,16c,19c-22:7), isolated from a marine alga, contains the same conjugated tetra-ene unit as α-parinaric acid.
Newer results for α- and β-eleostearic, punicic, and catalpic acids, collected in Table 5, differ from the older data in Table 3. The newer information is obtained from oils containing these acids and chemical shifts are given for both α and β chains. However, there is poor agreement between these two sets of data. This is illustrated for α-eleostearic acid in Table 6 where olefinic signals and assignments are compared.
Table 4. Chemical shifts (ppm) for natural acids with conjugated triene (Gunstone, 1993) and tetra-ene (Spitzer et al., 1996,1997) systems [trivial names punicic (a), α-eleostearic (b), catalpic (c), β-eleostearic(d), jacaric (e), calendic (f), α-parinaric (g), stellaheptaenoic (h)] | ||||||||
D-9,11,13 | D-8,10,12 | D-9,11,13,15 | D-4,7,9,11,13, 16,19 |
|||||
---|---|---|---|---|---|---|---|---|
ctc | ctt | ttc | ttt | ctc | ttc | cttc | ccttccc | |
a | b | c | d | e | f | g | h | |
5 | nc | nc | nc | nc | 28.89 | 28.85 | nc | 128.98 |
6 | nc | nc | nc | nc | nc | nc | nc | 26.61 |
7 | nc | nc | nc | nc | 27.81 | 32.78 | nc | 128.69 |
8 | 27.89 | 27.83 | 32.84 | 32.80 | 127.81# | 126.21# | 27.97 | 128.49 |
9 | 128.96 | 128.95 | 126.12# | 130.73 | 128.07# | 128.71# | 132.83 | 127.33 |
10 | 132.38 | 132.91 | 128.79# | 130.81 | 128.86# | 130.85# | 128.24 | 133.84 |
11 | 127.87 | 125.98 | 130.82# | 134.19 | 129.07# | 132.04# | 128.14 | 133.86 |
12 | 128.02 | 134.90 | 131.75# | 133.98 | 132.09# | 132.71# | 132.88 | 128.52 |
13 | 132.62 | 131.52 | 132.77# | 130.95 | 132.57# | 134.66# | 132.91 | 129.19 |
14 | 128.86 | 130.73 | 134.70# | 130.60 | 27.89 | 27.89 | 128.21 | 132.18 |
15 | 27.65 | 32.53 | 27.58 | 32.53 | nc | nc | 128.89 | 26.61 |
16 | 31.94 | 31.58 | 31.95 | 31.58 | 31.57 | 31.56 | 134.52 | 130.37 |
17 | 22.39 | 22.28 | 22.38 | 22.28 | 22.62 | 22.62 | 21.33 | 129.51 |
18 | 14.02 | 13.95 | 14.00 | 13.95 | 14.10 | 14.11 | 14.37 | 26.61* |
Table 5. Chemical shifts (ppm) for natural acids with conjugated triene systems (Blaise et al., 1997) | ||||||
A/α | A/β | B/α | B/β | C/α | C/β | |
---|---|---|---|---|---|---|
9 | 131.724 | 131.685 | 134.184 | 134.142 | 128.937 | 128.920 |
10 | 128.837 | 128.818 | 130.631 | 130.613 | 132.426 | |
11 | 125.986 | 125.965 | 130.798 | 130.782 | 127.858 | 127.840 |
12 | 132.926 | 132.906 | 130.963 | 130.942 | 128.025 | |
13 | 130.640 | 130.631 | 130.505 | 132.688 | 132.668 | |
14 | 135.164 | 135.141 | 134.444 | 134.426 | – | – |
(A) α-Eleostearic, (B) β-eleostearic, (C), punicic. Also, catalpic glycerol esters 134.897 (α), 132.760 (α), 131,973 (β), 131,957 (α), 128,715 (α and β), 126.148 (β), 126.132 (α), 130.755 (β), 130.741 (α). – These chemical shifts are not assigned to individual carbon atoms and it is not clear why 9 values are listed. |
Table 6. Chemical shifts (ppm) listed in increasing numerical value for olefinic carbon atoms in α-eleostearic acid according to Tulloch and Blaise | |||
Tulloch and Bergter (1979) | Blaise et al. (1997) | ||
---|---|---|---|
Shift (ppm) | Carbon atom | Shift (ppm) | Carbon atom |
125.98 | 11 | 125.99 | 11 |
128.95 | 9 | 128.84 | 10 |
130.73 | 14 | 130.64 | 13 |
131.52 | 13 | 131.72 | 9 |
134.90 | 12 | 135.16 | 14 |
References
- Blaise, P., Wolff, R. and Farines, M. Etude regiospecific de triacyglycerols d’huiles vegetales par clivage chimique et RMN 13C haute resolution, Oleagineux Corps gras Lipides, 4, 135-141 (1997).
- Davis, A.L., McNeill, G.P. and Caswell, D.C. Analysis of conjugated linoleic acid isomers by 13C-NMR spectroscopy. Chem. Phys. Lipids, 97, 155-165 (1999).
- Gunstone, F.D. High resolution 13C-NMR spectroscopy of lipids. In: Advances in Lipid Methodology – Two, pp. 1-68 (ed. W.W. Christie, Oily Press, Dundee) (1993).
- Lie Ken Jie, M.S.F., Pasha, M.K. and Ahmad, F. Ultrasound-assisted synthesis of santalbic acid and a study of triacylglycerol species in Santalum album (Linn.) seed oil. Lipids, 31, 1083-1089 (1996).
- Lie Ken Jie, M.S.F., Pasha, M.K. and Ahmad, F. Synthesis and nuclear magnetic resonance properties of all geometrical isomers of conjugated linoleic acids. Lipids, 32, 1041-1044 (1997).
- Mikhailova, M.V., Bemis, D.L., Wise, M.L., Gerwick, W.H., Norris, J.N. and Jacobs, R.S. Structure and biosynthesis of novel conjugated polyene fatty acids from the marine green alga Anadyomene stellata, Lipids, 30, 583-589 (1995).
- Spitzer, V., Tomberg, W., Hartmann, R. and Aichholz, R. Analysis of the seed oil of Heisteria silvanii (Olacaceae) – a rich source of a novel C18 acetylenic fatty acid, Lipids, 32, 1189-1200 (1997).
- Spitzer, V., Tomberg, W. and Zucolotto, M. Identification of α-parinaric acid in the seed oil of Sebastiana brasiliensis Sprengel (Euphorbiaceae). J. Am. Oil Chem. Soc., 73, 569-573 (1996).
- Tulloch, A.P. and Bergter, L. Analysis of the conjugated triene acid containing oil from Fevillea trilobata by 13C nuclear magnetic resonance spectroscopy. Lipids, 14, 996-1002 (1979).
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