Polyunsaturated fatty acid
Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic property.
Polyunsaturated fatty acids can be classified in various groups by their chemical structure:
- methylene-interrupted polyenes
- conjugated fatty acids
- other PUFAs
Based on the length of their carbon backbone, they are sometimes classified in two groups:[1]
- short chain polyunsaturated fatty acids (SC-PUFA), with 16 or 20 carbon atoms
- long-chain polyunsaturated fatty acids (LC-PUFA) with more than 18 carbon atoms
Types
Methylene-interrupted polyenes
These fatty acids have 2 or more cis double bonds that are separated from each other by a single methylene bridge (-CH
2-). This form is also sometimes called a divinylmethane pattern.[2]
| −C−C=C−C−C=C− |
The essential fatty acids are all omega-3 and -6 methylene-interrupted fatty acids. See more at Essential fatty acids—Nomenclature
Omega-3
| Common name | Lipid name | Chemical name |
|---|---|---|
| Hexadecatrienoic acid (HTA) | 16:3 (n-3) | all-cis 7,10,13-hexadecatrienoic acid |
| Alpha-linolenic acid (ALA) | 18:3 (n-3) | all-cis-9,12,15-octadecatrienoic acid |
| Stearidonic acid (SDA) | 18:4 (n-3) | all-cis-6,9,12,15,-octadecatetraenoic acid |
| Eicosatrienoic acid (ETE) | 20:3 (n-3) | all-cis-11,14,17-eicosatrienoic acid |
| Eicosatetraenoic acid (ETA) | 20:4 (n-3) | all-cis-8,11,14,17-eicosatetraenoic acid |
| Eicosapentaenoic acid (EPA, Timnodonic acid) | 20:5 (n-3) | all-cis-5,8,11,14,17-eicosapentaenoic acid |
| Heneicosapentaenoic acid (HPA) | 21:5 (n-3) | all-cis-6,9,12,15,18-heneicosapentaenoic acid |
| Docosapentaenoic acid (DPA, Clupanodonic acid) | 22:5 (n-3) | all-cis-7,10,13,16,19-docosapentaenoic acid |
| Docosahexaenoic acid (DHA, Cervonic acid) | 22:6 (n-3) | all-cis-4,7,10,13,16,19-docosahexaenoic acid |
| Tetracosapentaenoic acid | 24:5 (n-3) | all-cis-9,12,15,18,21-tetracosapentaenoic acid |
| Tetracosahexaenoic acid (Nisinic acid) | 24:6 (n-3) | all-cis-6,9,12,15,18,21-tetracosahexaenoic acid |
Omega-6
| Common name | Lipid name | Chemical name |
|---|---|---|
| Linoleic acid (LA) | 18:2 (n-6) | all-cis-9,12-octadecadienoic acid |
| Gamma-linolenic acid (GLA) | 18:3 (n-6) | all-cis-6,9,12-octadecatrienoic acid |
| Eicosadienoic acid | 20:2 (n-6) | all-cis-11,14-eicosadienoic acid |
| Dihomo-gamma-linolenic acid (DGLA) | 20:3 (n-6) | all-cis-8,11,14-eicosatrienoic acid |
| Arachidonic acid (AA) | 20:4 (n-6) | all-cis-5,8,11,14-eicosatetraenoic acid |
| Docosadienoic acid | 22:2 (n-6) | all-cis-13,16-docosadienoic acid |
| Adrenic acid (AdA) | 22:4 (n-6) | all-cis-7,10,13,16-docosatetraenoic acid |
| Docosapentaenoic acid (Osbond acid) | 22:5 (n-6) | all-cis-4,7,10,13,16-docosapentaenoic acid |
| Tetracosatetraenoic acid | 24:4 (n-6) | all-cis-9,12,15,18-tetracosatetraenoic acid |
| Tetracosapentaenoic acid | 24:5 (n-6) | all-cis-6,9,12,15,18-tetracosapentaenoic acid |
Omega-9
| Common name | Lipid name | Chemical name |
|---|---|---|
| Oleic acid† | 18:1 (n-9) | cis-9-octadecenoic acid |
| Eicosenoic acid† | 20:1 (n-9) | cis-11-eicosenoic acid |
| Mead acid | 20:3 (n-9) | all-cis-5,8,11-eicosatrienoic acid |
| Erucic acid† | 22:1 (n-9) | cis-13-docosenoic acid |
| Nervonic acid† | 24:1 (n-9) | cis-15-tetracosenoic acid |
| †Monounsaturated | ||
Conjugated fatty acids
| -C=C-C=C- |
| Common name | Lipid name | Chemical name |
|---|---|---|
| Conjugated Linoleic Acids (two conjugated double bonds) | ||
| Rumenic acid | 18:2 (n-7) | 9Z,11E-octadeca-9,11-dienoic acid |
| 18:2 (n-6) | 10E,12Z-octadeca-10,12-dienoic acid | |
| Conjugated Linolenic Acids (three conjugated double bonds) | ||
| α-Calendic acid | 18:3 (n-6) | 8E,10E,12Z-octadecatrienoic acid |
| β-Calendic acid | 18:3 (n-6) | 8E,10E,12E-octadecatrienoic acid |
| Jacaric acid | 18:3 (n-6) | 8Z,10E,12Z-octadecatrienoic acid |
| α-Eleostearic acid | 18:3 (n-5) | 9Z,11E,13E-octadeca-9,11,13-trienoic acid |
| β-Eleostearic acid | 18:3 (n-5) | 9E,11E,13E-octadeca-9,11,13-trienoic acid |
| Catalpic acid | 18:3 (n-5) | 9Z,11Z,13E-octadeca-9,11,13-trienoic acid |
| Punicic acid | 18:3 (n-5) | 9Z,11E,13Z-octadeca-9,11,13-trienoic acid |
| Other | ||
| Rumelenic acid | 18:3 (n-3) | 9E,11Z,15E-octadeca-9,11,15-trienoic acid |
| α-Parinaric acid | 18:4 (n-3) | 9E,11Z,13Z,15E-octadeca-9,11,13,15-tetraenoic acid |
| β-Parinaric acid | 18:4 (n-3) | all trans-octadeca-9,11,13,15-tetraenoic acid |
| Bosseopentaenoic acid | 20:5 (n-6) | 5Z,8Z,10E,12E,14Z-eicosapentaenoic acid |
Other polyunsaturated fatty acids
| Common name | Lipid name | Chemical name |
|---|---|---|
| Pinolenic acid | 18:3 (n-6) | (5Z,9Z,12Z)-octadeca-5,9,12-trienoic acid |
| Podocarpic acid | 20:3 (n-6) | (5Z,11Z,14Z)-eicosa-5,11,14-trienoic acid |
Function and effects
The biological effects of the ω-3 and ω-6 fatty acids are largely mediated by their mutual interactions, see Essential fatty acid interactions for detail.
Thermal degradation
Polyunsaturated fatty acids in culinary oils undergo oxidative deterioration at temperatures of 150 °C (302 °F). The heating causes a free radical chain reaction, which oxidizes the PUFAs into hydroperoxide, which further decomposes into a complex mixture of secondary products.[3]
See also
References
Citations
- Buckley MT, et al. (2017). "Selection in Europeans on Fatty Acid Desaturases Associated with Dietary Changes". Mol Biol Evol. 34 (6): 1307–1318. doi:10.1093/molbev/msx103. PMC 5435082. PMID 28333262.
- Baggott, James (1997). The divinylmethane pattern in fatty acids. Salt Lake City, UT: Knowledge Weavers.
- Moya Moreno, MC; Mendoza Olivares, D; Amézquita López, FJ; Gimeno Adelantado, JV; Bosch Reig, F (September 13, 1999). "Analytical evaluation of polyunsaturated fatty acids degradation during thermal oxidation of edible oils by Fourier transform infrared spectroscopy". Talanta. 50 (2): 269–75. doi:10.1016/S0039-9140(99)00034-X. PMID 18967717.
General References
- Cyberlipid. "Polyenoic Fatty Acids". Archived from the original on 2018-09-30. Retrieved 2007-01-17.
- Gunstone, Frank D. "Lipid Glossary 2" (PDF). Archived from the original (PDF) on 2006-08-13. Retrieved 2007-01-17.
- Adlof, R. O. & Gunstone, F. D. (2003-09-17). "Common (non-systematic) Names for Fatty Acids". Archived from the original on 2006-12-06. Retrieved 2007-01-24.
- Heinz; Roughan, PG (1983). "Similarities and Differences in Lipid Metabolism of Chloroplasts Isolated from 18:3 and 16:3 Plants". Plant Physiol. 72 (2): 273–279. doi:10.1104/pp.72.2.273. PMC 1066223. PMID 16662992.
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