Elaidic acid is a monounsaturated fatty acid containing 18 carbon chains in a trans configuration, and is a structural isomer of oleic acid, therefore with a structure equal to oleic acid, but unfortunately with the important difference, being a trans fatty acid.

It is a trans unsaturated fatty acid belonging to the family of monounsaturated fatty acids. It is the trans form of oleic acid, a more common fatty acid in its cis configuration. Elaidic acid is primarily known for its use in processed food products and, to a lesser extent, in industrial applications. Due to its trans structure, elaidic acid is more rigid than cis fatty acids, and excessive consumption is associated with negative health effects.

Chemical Composition and Structure

Elaidic acid has the chemical formula C₁₈H₃₄O₂. It is an 18-carbon fatty acid with a single trans double bond between the ninth and tenth carbon atoms, distinguishing it from oleic acid, which has a cis configuration. Its trans structure makes it less flexible and more linear, giving it a higher melting point compared to cis fatty acids.

Physical Properties

It appears as a white or yellowish solid at room temperature, with a higher melting point than its cis counterpart, oleic acid. This makes it suitable for use in processed foods where a stable, solid fat is required. It is soluble in organic solvents and has hydrophobic properties.

Production Process

Elaidic acid is typically produced through the partial hydrogenation of vegetable oils. During this process, oils containing unsaturated fatty acids (such as oleic acid) are treated with hydrogen, converting some of the cis double bonds into trans double bonds, resulting in elaidic acid and other trans fats.

• Extraction of Vegetable Oils: Vegetable oils containing oleic acid, such as olive oil, sunflower seed oil, or soybean oil, are extracted from plant sources. This can be done through mechanical pressing or solvent extraction.

• Hydrogenation: The extracted oleic acid is subjected to a hydrogenation process, where it is treated with hydrogen in the presence of a catalyst (usually nickel) to modify the chemical structure of oleic acid, converting it into elaidic acid. During this process, the double bonds in the carbon chain are altered, generating the trans isomer of oleic acid.

• Purification: The produced elaidic acid is purified to remove any impurities and chemical residues. This may include distillation or refining processes to achieve a high-quality product.

• Quality Control and Packaging: Finally, elaidic acid undergoes quality control checks to verify its purity and functional properties. After analysis, it is packaged for distribution and use in food and cosmetic products.

Applications

• Food Industry: Elaidic acid is commonly found in processed foods containing trans fats, such as margarine, snacks, and baked goods, where it is used to improve texture and extend shelf life.

• Industrial Applications: In some industrial settings, elaidic acid is used as a chemical precursor or stabilizing agent due to its increased rigidity and stability compared to cis fatty acids.

Where is it ?

It is found in margarine and fried foods.

Health and Safety Considerations

Safety in Use
The use of elaidic acid in food products has been criticized due to its negative health effects. Excessive consumption of trans fats, including elaidic acid, has been linked to an increased risk of cardiovascular diseases, obesity, and diabetes. As a result, many international regulations have restricted or banned the use of artificial trans fats in food products.

Allergic Reactions
There is no evidence to suggest that elaidic acid causes allergic reactions. However, consuming products containing trans fats may contribute to inflammatory conditions and long-term health problems.

Toxicity and Carcinogenicity
Studies have shown that trans fats, including those containing elaidic acid, can have harmful effects on health, increasing LDL (bad) cholesterol levels and lowering HDL (good) cholesterol levels, leading to cardiovascular health risks. While it is not considered directly carcinogenic, its consumption is discouraged due to its long-term impact on metabolism and cardiovascular health.

Environmental and Safety ConsiderationsFrom an environmental perspective, elaidic acid does not pose significant concerns as it is biodegradable. However, the partial hydrogenation process used to produce it has an environmental impact, as it requires energy and chemical resources.

Regulatory Status
Due to the health risks associated with trans fats, many countries, including the European Union and the United States, have imposed restrictions or banned the use of artificial trans fats in food products. Regulations limit the amount of elaidic acid and other trans fats allowed in commercial products.

Studies

339 German foods of six categories (semi-solid fats, deep-fried potato products, bakery products, confectioneries, instant products and butter) were analysed using two GC methods.
In samples containing ruminant fat (butter and various confectioneries), vaccenic acid (t11-C18:1, t11) predominated, while in foods containing industrially hydrogenated fats, elaidic acid (trans-9, t9-) and t10-C18:1 were the major trans isomers (1).

Trans fatty acids (TFAs) are risk factors for cardiovascular disorders, and the cancer-promoting effects of TFAs have been previously reported. The present study examined the effects and signaling of elaidic acid (EA), a TFA, in colorectal cancer (CRC) cells. Oral intake of EA was found to increase metastasis of HT29 human CRC cells. Results indicated that, in the plasma membrane, EA was integrated into cholesterol rafts, which contain epidermal growth factor receptors (EGFR). EA increased nanog and c-myc, and decreased PGC-1A through lipid raft-associated EGFR signaling in HT29 cells. Depletion of cholesterol by methyl-β-cyclodextrin treatment abrogated the EA-induced stemness and oxidative phosphorylation. Simvastatin treatment also abrogated EA-enhanced tumor growth. These results indicate that EA enhances the stemness by activating EGFR in lipid rafts (2).

Intake of trans fatty acids (TFA), which are consumed by eating foods made from partially hydrogenated vegetable oils, is associated with a higher risk of cardiovascular disease. This relation can be explained by many factors including TFA's negative effect on endothelial function and reduced nitric oxide (NO) bioavailability. This study investigated the effects of three different TFA (2 common isomers of C18 found in partially hydrogenated vegetable oil and a C18 isomer found from ruminant-derived-dairy products and meat) on endothelial NF-κB activation and nitric oxide (NO) production. Human endothelial cells were treated with increasing concentrations of Elaidic (trans-C18:1 (9 trans)), Linoelaidic (trans-C18:2 (9 trans, 12 trans)), and Transvaccenic (trans-C18:1 (11 trans)) for 3 h. Both Elaidic and Linoelaidic acids were associated with increasing NF-κB activation as measured by IL-6 levels and phosphorylation of IκBα, and impairment of endothelial insulin signaling and NO production, whereas Transvaccenic acid was not associated with these responses. Superoxide production, which has been hypothesized to be necessary in fatty acid-dependent activation of NF-κB was measured. Both Elaidic acid and Linoelaidic acid are associated with increased superoxide production, whereas Transvaccenic acid (which did not induce inflammatory responses) did not increase superoxide production. Differential activation of endothelial superoxide production, NF-κB activation, and reduction in NO production by different C18 isomers was observed, suggesting that the location and number of trans double bonds effect endothelial NF-κB activation (3).

BACKGROUND: Nutritional choices, which include the source of dietary fatty acids (FA), have an important significant impact on coronary artery disease (CAD). This study aimed to determine on patients with CAD the relationships between Trans fatty acids (Trans FA) and different CAD associated parameters such as inflammatory and oxidative stress parameters in addition to Gensini score as a vascular severity index. METHODS: Fatty acid profiles were established by gas chromatography from 111 CAD patients compared to 120 age-matched control group. Lipid peroxidation biomarkers, oxidative stress, inflammatory parameters and Gensini score were studied. RESULTS: This study showed a significant decrease of the antioxidant parameters levels such as erythrocyte glutathione peroxydase (GPx) and superoxide dismutase (SOD) activities, plasma antioxidant status (FRAP) and thiol (SH) groups in CAD patients. On the other hand, catalase activity, conjugated dienes and malondialdehyde were increased. Plasmatic and erythrocyte Trans FA were also increased in CAD patients compared to controls. Furthermore, divergent associations of these Trans FA accumulations were observed with low-density lipoprotein-cholesterol/ high-density lipoprotein-cholesterol (LDL-C/HDL-C) ratio, Apolipoprotein B (ApoB), lipid peroxidation parameters, high-sensitivity C Reactive Protein (hs-CRP), Interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α) and Gensini score. Especially, elaidic acid (C18:1 trans 9), trans C18:2 isomers and trans 11 eicosanoic acid are correlated with these parameters. Trans FA are also associated with oxidative stress, confirmed by a positive correlation between C20:1 trans 11 and GPx in erythrocytes. CONCLUSIONS: High level of Trans FA was highly associated with the induction of inflammation, oxidative stress and lipoperoxidation which appear to be based on the vascular severity and might be of interest to assess the stage and progression of atherosclerosis. The measurement of these Trans FA would be of great value for the screening of lipid metabolism disorders in CAD patients (4).

• Linear Formula  CH₃(CH₂)₇CH=CH(CH₂)₇COOH
• Formula molecolare  C₁₈H₃₄O₂
• Peso molecolare  282.468 g/mol
• CAS  112-79-8
• UNII   4837010H8C
• EC number   204-006-6
• Nikkaji    J199.825K    J10.103F

Synonyms :

• Elaidic acid
• 9-octadecenoic acid
• EINECS 204-006-6
• UNII-4837010H8C
• elaidate

References_____________________________________________________________________

(1) Kuhnt K, Baehr M, Rohrer C, Jahreis G. Trans fatty acid isomers and the trans-9/trans−11 index in fat containing foods.   Eur. J. Lipid Sci. Technol. 2011;113:1281–1292.

(2) Kishi S, Fujiwara-Tani R, Luo Y, Kawahara I, Goto K, Fujii K, Ohmori H, Nakashima C, Sasaki T, Kuniyasu H. Pro-metastatic signaling of the trans fatty acid elaidic acid is associated with lipid rafts. Oncol Lett. 2018 Apr;15(4):4423-4426. doi: 10.3892/ol.2018.7817. Epub 2018 Jan 17 

(3) Iwata NG, Pham M, Rizzo NO, Cheng AM, Maloney E, Kim F. Trans fatty acids induce vascular inflammation and reduce vascular nitric oxide production in endothelial cells.  PLoS One. 2011;6(12):e29600. doi: 10.1371/journal.pone.0029600. Epub 2011 Dec 28.

(4) Hadj Ahmed S, Kharroubi W, Kaoubaa N, Zarrouk A, Batbout F, Gamra H, Najjar MF, Lizard G, Hininger-Favier I, Hammami M. Correlation of trans fatty acids with the severity of coronary artery disease lesions.  Lipids Health Dis. 2018 Mar 15;17(1):52. doi: 10.1186/s12944-018-0699-3