Eicosenoic Acid (C20:1): A Comprehensive Reference
1. Identity, Chemical Nomenclature, and Classification
Eicosenoic acid is not a single compound but a collective term for a family of 20-carbon monounsaturated fatty acids (MUFAs), each distinguished by the position and geometry of its sole double bond. Eicosenoic acid may refer to one of three closely related chemical compounds: 9-eicosenoic acid (gadoleic acid), an omega-11 fatty acid (20:1Ο11); 11-eicosenoic acid (gondoic acid), an omega-9 fatty acid (20:1Ο9); and 13-eicosenoic acid (paullinic acid), an omega-7 fatty acid (20:1Ο7). All three share the same molecular formula C20H38O2 and molecular weight of approximately 310.51 g/mol.
In nutritional and biochemical literature, the term "eicosenoic acid" is most often used to indicate the C20:1 fatty acid class broadly, while specific isomers are referred to by their trivial names. Eicosenoic acid is a long-chain monounsaturated fatty acid (C20:1); the trivial names for the 9-cis and 11-cis isomers are gadoleic acid and gondoic acid, respectively.
1.1 Major Isomers in Detail
- 9-Eicosenoic acid (gadoleic acid; 20:1n-11; CAS 29204-02-2): Gadoleic acid (20:1 nβ11) is an unsaturated fatty acid and a prominent component of some fish oils including cod liver oil. Its name is derived from a combination of the genus for cod (Gadus) and the Latin word oleum (oil).
- 11-Eicosenoic acid (gondoic acid; 20:1n-9; CAS 5561-99-9): 11-Eicosenoic acid, also called gondoic acid, is a monounsaturated omega-9 fatty acid found in a variety of plant oils and nuts; in particular jojoba oil. Its IUPAC name is (11Z)-icos-11-enoic acid.
- 13-Eicosenoic acid (paullinic acid; 20:1n-7; CAS 17735-94-3): 13-Eicosenoic acid (paullinic acid) is an omega-7 fatty acid that occurs in several seed oils.
Eicosenoic acid is a monounsaturated long-chain fatty acid with a 20-carbon backbone and the sole double bond originating from the 5th, 6th, 7th, 9th, 11th, 12th or 15th positions from the methyl end. Eicosenoic acid has a role as both a plant metabolite and a human metabolite. Eicosenoic acid is not soluble in water and exhibits weak acidity.
2. Natural Sources and Distribution
2.1 Plant Sources
Jojoba (Simmondsia chinensis) is the most concentrated botanical source of eicosenoic acid. The combined C20:1 isomers constitute 70% of the total fatty acid pool in jojoba seed oil isolated from plants in the Arizona desert. Jojoba seeds produce 50% to 55% by weight of a colorless, odorless oil or liquid wax; the wax is almost completely (97%) composed of straight chain monoesters of C-20 and C-22 acids and alcohols with two double bonds, with the acids identified as a mixture of cis-11-eicosenoic (C-20) and cis-13-docosenoic (C-22, erucic) acids.
Meadowfoam (Limnanthes alba) is another rich source. In plants, 5Z-20:1 can amount to 67% of the total fatty acids in meadowfoam oil. The major fatty acids in meadowfoam oil include 5-eicosenoic, 11-eicosenoic, 5-docosenoic, 13-docosenoic, and 5,13-docosadienoic acids.
Brassica and related oilseeds: 11Z-eicosenoic acid is a common if minor constituent of animal tissues and fish oils, often accompanied by the 13-isomer; in plants, it is present in rapeseed oil and seed oils of other Brassicas. Very-long-chain monounsaturated fatty acids (VLCFAs), including eicosenoic acid (20:1), from meadowfoam (Limnanthes alba), crambe (Crambe abyssinica), Brassica napus, and Brassica carinata are widely used in cosmetics, lubricants, and plastic films.
Other plant sources: Eicosenoic acid C20:1 is one of the fatty acids that have been identified in hemp (cannabis) seed oil. In Arabidopsis thaliana seed triacylglycerol (TAG), 11-eicosenoic acid (20:1) is the predominant very-long-chain fatty acid (VLCFA). The embryonic cells of the Brassicaceae and jojoba (Simmondsia chinensis) accumulate VLCFAs as seed oil storage compounds (triacylglycerols and wax, respectively), which constitute an enormous energy investment by the entire parent plant.
2.2 Animal and Marine Sources
11Z-Eicosenoic acid is a common if minor constituent of animal tissues and fish oils, often accompanied by the 13-isomer. Gadoleic acid (9-eicosenoic acid, 20:1n-11) is particularly associated with marine sources. The omega-11 fish oil fraction is characterized by 20:1 n-11 (cis-9-eicosenoic acid or gadoleic acid) and 22:1 n-11 (cis-9-cetoleic acid). Fatty acids with aliphatic tails exceeding 18 carbon atoms, including gadoleic acid (C20:1) and cetoleic acid (C22:1) isomers, have been identified for their potential efficacy in modulating hyperlipidemia. Very-long-chain monoenoic fatty acids of the (n-9) family occur in a variety of natural sources, often accompanied by analogous fatty acids of the (n-7) family in animal tissues, and those from 20:1 to 26:1 are normal constituents of sphingolipids from both animals and plants.
2.3 Endogenous Status in Humans
Eicosenoic acid is not synthesized by humans but must be obtained through diet. Eicosenoic acid is a natural product found in Simmondsia chinensis, Homo sapiens, and other organisms, indicating that while dietary eicosenoic acid is incorporated into human tissues, the acid is not significantly produced de novo by human metabolism.
3. Traditional and Historical Use
Eicosenoic acid itself has no direct historical use in herbal or traditional medicine, as it was identified and studied only in the 20th century, primarily through fatty acid analysis of oils and seeds. However, the botanical sources richest in this fatty acid β particularly jojoba β carry well-documented ethnobotanical histories.
3.1 Jojoba in Native American Traditions
Native Americans first made use of jojoba. During the early 18th century, Jesuit missionaries on the Baja California Peninsula observed indigenous peoples heating jojoba seeds to soften them; they then used a mortar and pestle to create a salve or buttery substance. The latter was applied to the skin and hair to heal and condition. The O'odham people of the Sonoran Desert treated burns with an antioxidant salve made from a paste of the jojoba seed. Native Americans also used the salve to soften and preserve animal hides. Pregnant women ate jojoba seeds, believing they assisted during childbirth.
Native American cultures of the southwestern deserts utilized jojoba oil to treat skin conditions as well as cosmetically rubbing it on their hair and bodies as a protectant. For a long time, American Indians and Mexicans have used jojoba oil as a hair conditioner/restorer and as a medicine, as well as in cooking and rituals.
Several distinct indigenous nations used jojoba for specific purposes. The Cahuilla used the oil paste from the seed to treat sores and wounds. The Tohono O'odham people of southwestern U.S. used the jojoba plant as a dermatological aid; they pulverized the seed and created a poultice of parched seed material, and holding this poultice against the skin helped heal skin issues. The O'odham Native American tribe extracted the oil from jojoba seeds to treat sores and wounds. The large edible seeds contain about 50% oil, which is directly used as a cooking oil and as a hair oil, and the oil has excellent qualities for many industrial and medicinal uses.
The common name "jojoba" carries its own linguistic history. The common name "jojoba" originated from the O'odham name Hohowi. Jojoba joined the industrial world during World War II as a substitute for dwindling supplies of other oil resources.
3.2 Other Traditional Contexts
Guarana, a source of paullinic acid (13-eicosenoic acid), has been used in Amazonian herbal medicine for energy, cognition, and digestive support, though this use relates more to its caffeine content than its fatty acid profile.
4. Chemistry, Biosynthesis, and Key Constituents
4.1 Chemical Structure and Properties
All eicosenoic acid isomers share the formula C20H38O2 with a molecular weight of 310.51 g/mol. The position and geometry (cis/trans) of the single double bond differentiate the biological properties of each isomer. 11(E)-Eicosenoic acid is a very long-chain Ο-9 fatty acid that is a trans monounsaturated isomer of arachidic acid. It is one of several monounsaturated 20-carbon fatty acids used to study phospholipid membranes.
4.2 Biosynthesis and Elongation
In plants, eicosenoic acid is produced by the elongation of C18 fatty acids. VLCFAs are elongated by an endoplasmic reticulum-localized fatty acid elongation complex of four core enzymes, which sequentially add two carbon units to a growing acyl chain. A fourth component of the elongation complex, the condensing enzyme, provides substrate specificity and determines the amount of product synthesized by the entire complex; land plants have two families of condensing enzymes, FATTY ACID ELONGATION 1 (FAE1)-type ketoacyl-CoA synthases (KCSs) and ELONGATION DEFECTIVE-LIKEs (ELO-LIKEs).
In Arabidopsis thaliana, the primary genetic determinants of eicosenoic acid content in seeds have been studied. Four quantitative trait loci (QTL) for the quantity of the major very-long-chain fatty acid species 11-eicosenoic acid (20:1) have been mapped using multiple QTL modelling; surprisingly, the main-effect QTL does not coincide with FATTY ACID ELONGASE 1, and a parallel genome-wide association study suggested that LYSOPHOSPHATIDYLCHOLINE ACYLTRANSFERASE 2 (LPCAT2) is a candidate for this QTL.
In mammals, the elongase enzymes ELOVL1β7 regulate very-long-chain fatty acid synthesis. Elongases catalyze the first of four steps in the VLCFA elongation cycle; mammals have seven elongases (ELOVL1β7). Particularly notable was the high activity exhibited by ELOVL1 toward saturated and monounsaturated C20- and C22-CoAs, and its essential role in the production of C24 sphingolipids.
4.3 Role as a VLCFA in Sphingolipids
Only a very small fraction of VLCFA occurs unesterified; the main fraction of intracellular VLCFA is esterified in various lipids. Under normal circumstances, a substantial amount of VLCFA is amide-linked to a long-chain sphingoid base sphinganine, forming a ceramide, which constitutes the lipid backbone of sphingomyelin and other sphingolipids. The distribution of VLCFA between sphingolipids and glycerolipids is controlled by the substrate specificity of the corresponding fatty acyltransferases, such as ceramide synthase. Sphingolipids are essential for cell proliferation; impaired sphingolipid synthesis leads to cessation of cell growth both in yeast and mammalian cells.
5. Mechanisms of Action
5.1 Inhibition of Phospholipid Biosynthetic Enzymes
11(E)-Eicosenoic acid has been shown to inhibit glycerophosphate acyltransferase, cholinephosphotransferase, and ethanolaminephosphotransferase in V79-R cells. These are key enzymes in the Kennedy pathway responsible for de novo phospholipid synthesis, suggesting that the trans-isomer of gondoic acid can interfere with membrane phospholipid assembly at the cellular level.
5.2 Telomerase Activity (Isomer-Specific Null Effect)
11(E)-Eicosenoic acid lacks the cis-double bond and has virtually no effect on telomerase activity, unlike cis-unsaturated C20 fatty acids, which demonstrate strong telomerase inhibition and have been studied as a promising cancer therapeutic target. This finding highlights that the biological activity of eicosenoic acid isomers is strongly dependent on double-bond geometry; the trans form is inactive at telomerase, while certain cis-isomers are active.
5.3 Anti-Inflammatory Signaling
Kupffer cells (KCs) are the main macrophage population in the liver, and their inflammation is related to liver diseases; it has been shown that inflammatory macrophages are accompanied by changes in monounsaturated fatty acid (MUFA) content. Gondoic acid (GA) significantly inhibited the expression of pro-inflammatory factors in LPS-exposed KCs; GA reduced lipopolysaccharide (LPS)-stimulated reactive oxygen species (ROS) levels and enhanced the expression of antioxidant genes; meanwhile, GA obviously blocked the LPS-stimulated PKCΞΈ/ERK/STAT3 signaling pathways to alleviate inflammatory responses.
5.4 Cell Membrane Structural Role
This fatty acid, although less commonly discussed compared to omega-3 and omega-6 fatty acids, plays a significant role in maintaining healthy cell membranes and metabolic functions. In plant systems, eicosenoic acid as a VLCFA is incorporated into sphingolipids and phospholipids, modulating membrane fluidity and integrity. Membrane phospholipids such as phosphatidylcholine (PC), phosphatidylethanolamine (PE) and especially phosphatidylserine (PS) preferentially incorporate saturated C20, C22 and C24 VLCFAs, while sphingolipids accumulating in the outer leaflet of the plasma membrane (PM) are often enriched in Ξ±-hydroxylated saturated and monounsaturated C24 and C26 VLCFAs.
5.5 Lipid Metabolism Modulation
Omega-9 fatty acids such as oleic acid decrease cholesterol ester transfer protein (CETP) levels, a protein that mediates the transfer of cholesteryl esters from HDL to apolipoprotein B-containing lipoproteins; the isoenergetic replacement of a high-saturated fatty acid diet by a MUFA or a high-carbohydrate low-fat diet has been shown to decrease CETP concentration in young, healthy, normolipidemic subjects. In animal studies, LCMUFA-rich diets improved the adipocytokine profile and resulted in favorable changes in triglycerides and LDL-C and in the expression of several genes involved in glucose/lipid metabolism and inflammation.
6. Scientific Evidence by Area of Research
6.1 Inflammation β Liver (Preclinical, In Vitro)
The most directly studied biological activity of gondoic acid (11-eicosenoic acid) is its anti-inflammatory action in hepatic macrophages. A 2022 study published in International Immunopharmacology (Fan G. et al., PMID 35998508) investigated gondoic acid's effect on LPS-stimulated Kupffer cells. The effect of gondoic acid (GA) on inflammation and its underlying mechanism had not previously been described; in the current study, GA significantly inhibited the expression of pro-inflammatory factors in LPS-exposed KCs; further research found that GA reduced LPS-stimulated reactive oxygen species (ROS) levels and enhanced the expression of antioxidant genes. The potential mechanism of GA's anti-inflammatory effect was identified as the inhibition of ROS production and the PKCΞΈ/ERK/STAT3 signaling pathway; the outcomes may provide fundamental insight for considering nutraceutical development for GA and will assist in the potential development of functional foods or prodrugs based on eicosenoic acid-rich plant oils.
Evidence strength: This evidence is entirely preclinical (cell-based, in vitro). No human clinical trials have been conducted on eicosenoic acid's anti-inflammatory effect.
6.2 Lipoprotein Metabolism and Cardiovascular Health
The potential of long-chain MUFAs, including gadoleic acid (9-eicosenoic acid), to modulate lipid profiles has attracted investigational interest. Fatty acids with aliphatic tails exceeding 18 carbon atoms, including gadoleic acid (C20:1) and cetoleic acid (C22:1) isomers, have been identified for their potential efficacy in modulating hyperlipidemia. A study (NCT03043365) was registered with ClinicalTrials.gov to examine the effect of fish oil enriched in omega-11 fatty acid (gadoleic acid) on lipoprotein metabolism in adults. Except for one past study which examined the effect of saury fish consumption on post-prandial lipids and glucose, no previous studies had investigated the effect of long-term supplementation of fish oil produced from saury fish on plasma lipoproteins or other outcomes. The mechanisms involved in the physiological effects of beneficial fatty acids, such as EPA, oleic acid, and LCMUFA are only partially understood.
Fish oil rich in DHA and EPA shows promise as an anti-hyperlipidemic agent; one study explored the synergistic lipid-lowering effects between long-chain monounsaturated fatty acids, EPA, and DHA using network pharmacology and experimental validation in HepG2 cells; various fish oils, particularly Engraulis japonicus and Pacific saury, effectively reduced oleic acid-induced lipid accumulation; network pharmacology identified 64 potential targets for fish oil fatty acids' synergistic anti-hyperlipidemic action; validation revealed superior impact on upregulating CPT1A and RXRA mRNA, promoting lipid metabolism, and suppressing SCD and FABP1 mRNA, inhibiting lipid synthesis.
Evidence strength: The evidence for eicosenoic acid's independent cardiovascular effects in humans is very limited. Most clinical data come from fish oil studies where EPA and DHA are the primary active components. No completed, published randomized controlled trial has isolated the specific effect of gadoleic or gondoic acid alone on human lipoprotein profiles.
6.3 Cell Membrane Function
11(E)-Eicosenoic acid is one of several monounsaturated 20-carbon fatty acids and is used to study phospholipid membranes. Research at the cellular level has demonstrated its incorporation into and effects on membrane phospholipid composition. Eicosenoic acid has been shown to inhibit glycerophosphate acyltransferase, cholinephosphotransferase, and ethanolaminephosphotransferase in V79-R cells. These are in vitro findings and have not been validated in human physiological studies.
6.4 Association with Autism Spectrum Disorder
An observational association between elevated eicosenoic acid in red blood cell membranes and autism spectrum disorder has been reported in the literature. Eicosenoic acid has been found in the red blood cell membrane with increased concentrations in children with regressive autism. Elevated levels of this fatty acid might indicate increased fatty acid catabolism, an alternative energy source in the brain when mitochondrial glycolytic energy generation is insufficient.
Evidence strength: This is an observational biomarker finding only. Research has shown that increased concentrations of gondoic acid in the red blood cell membrane are associated with higher levels observed in children with regressive autism; this suggests a potential link between gondoic acid levels and certain health conditions, although further research is needed to fully understand this association. No causal relationship has been established, and no intervention studies have been conducted.
6.5 Telomerase Inhibition and Cancer Research (Isomer-Specific)
Unlike other eicosenoic fatty acids, 11(E)-eicosenoic acid does not inhibit leukotriene B4 (Ki = 1,150 Β΅M in a radioligand binding assay in pig neutrophil membranes) or affect telomerase activity. By contrast, certain cis-unsaturated C20 fatty acids do demonstrate strong telomerase inhibition, an area of early-stage pharmaceutical research. The relevance of this distinction to dietary supplementation with natural-source eicosenoic acid (predominantly the cis forms from plant oils) remains under investigation and has not advanced to human clinical trials.
6.6 Genetic Lipid Metabolism Research
In plant genetics, eicosenoic acid has served as a research model for understanding seed oil elongation pathways. Four QTL for the quantity of the major VLCFA species 11-eicosenoic acid (20:1) have been mapped using multiple QTL modelling in a MAGIC population of Arabidopsis thaliana. The broad-sense heritability (HΒ²) for 20:1 content was high (0.85), indicating that seed eicosenoic acid content is strongly genetically controlled β a finding important for oilseed crop breeding rather than for human health.
7. Body Systems and Health Areas of Association
- Hepatic / Immune system: Gondoic acid has demonstrated preclinical activity in modulating inflammation in hepatic Kupffer cells via the PKCΞΈ/ERK/STAT3 pathway and by suppressing reactive oxygen species.
- Cardiovascular system: This fatty acid plays a significant role in maintaining healthy cell membranes and metabolic functions. Long-chain MUFAs including gadoleic acid are under investigation for effects on lipid profiles, with animal studies showing promise.
- Neurological / Red blood cell membrane: Elevated levels of 11Z-eicosenoic acid have been observed in the red blood cell membranes of children with regressive autism. This is an area of observational association, not established clinical utility.
- Skin and dermatology: Through its primary carrier, jojoba oil, eicosenoic acid is associated with wound healing, skin moisturization, and emollient effects. Gondoic acid can be used as a raw material for medical supplies and a moisturizing ingredient in cosmetic creams.
- Cellular membrane integrity: As a VLCFA substrate, eicosenoic acid contributes to the sphingolipid and phospholipid composition of plasma membranes across human, animal, and plant cells.
- Energy metabolism: Adequate levels of gondoic acid are important for energy production and the synthesis of important biological molecules.
8. Dosage Forms and Preparations
Eicosenoic acid is not marketed as an isolated dietary supplement in purified form for human consumption. It is encountered primarily as a naturally occurring fatty acid component within whole oils and foods. Today, eicosenoic acid is most commonly encountered in natural skin care, dermatological products, and lipid research, where it supports skin health, hydration, and gentle anti-inflammatory effects, particularly in sensitive or dry skin conditions.
- Topical (Jojoba oil): Jojoba oil is commonly used in dermatological preparations; there is no clinical evidence to guide dosage of jojoba or its oil, and it is primarily used as a vehicle for oxidation-sensitive substances in ointments.
- Dietary (fish and plant oils): Gadoleic acid is consumed incidentally as part of fish oils (particularly from cod, Atlantic herring, saury, and mackerel), while gondoic acid is consumed as part of rapeseed oil, nuts, and jojoba-containing products. No established dietary reference value or recommended intake level exists specifically for eicosenoic acid isomers from any regulatory body.
- Research grade: 11(E)-Eicosenoic acid is one of several monounsaturated 20-carbon fatty acids used to study phospholipid membranes. Purified preparations (e.g., CAS 5561-99-9) are available from chemical suppliers for laboratory research purposes only.
Regarding the omega-11-enriched fish oil clinical trial (NCT03043365), the study aimed to examine omega-11 fatty acid-enriched fish oil and understand its effect on cardiovascular health, with researchers wanting to study the long-chain monounsaturated fatty acid fraction. No published completed results citing a specific eicosenoic acid dose were available in the sources examined at the time of this article's preparation.
9. Safety Considerations
9.1 Eicosenoic Acid as an Isolated Compound
Little research exists on the health benefits or toxicity of eicosenoic acid. No established tolerable upper intake level (UL), no-observed-adverse-effect level (NOAEL), or acceptable daily intake (ADI) has been published by regulatory bodies such as EFSA, FDA, or WHO for eicosenoic acid as an isolated compound.
9.2 Jojoba Oil β Topical Use
Jojoba oil, the richest source of dietary or topically applied eicosenoic acid, has a well-characterized safety profile for topical use. One of the unusual attributes of jojoba oil is that it does not oxidize or become rancid. Case reports of contact dermatitis, confirmed by skin patch tests, exist for jojoba oil.
9.3 Ingestion of Jojoba β Specific Toxicological Concern
Although absolute contraindications have not been identified, jojoba should not be ingested by humans due to potential toxicity; information regarding safety and efficacy in pregnancy and lactation is lacking; adverse toxicological studies in rodents and birds exist. The principal toxicological concern with jojoba seed products is not eicosenoic acid itself but the co-occurring glucoside, simmondsin. A new toxic glucoside from jojoba meal called simmondsin has been isolated and identified; preliminary rat and mouse toxicological data implicate the benzyl cyanide derivative of simmondsin as the toxicant. The group of simmondsin compounds (10% to 20%) in jojoba seed meal, recognized as food-intake inhibitors, are removed before the meal can be used as animal feed. Importantly, simmondsin is concentrated in the seed meal (protein fraction) after oil extraction; the expressed oil itself contains little to no simmondsin, though even the oil should not be ingested.
9.4 Structural Distinction from Erucic Acid
Eicosenoic acid (C20:1) is structurally related to erucic acid (C22:1), a fatty acid associated with cardiac lipidosis in animal studies at high dietary levels. Erucic acid is the trivial name for the monounsaturated fatty acid docosenoic acid (C22:1, 13-cis); it is present in seed oils of the Cruciferae family such as rape, mustard and crambe; modern varieties of rapeseed oils have been bred to contain less than 2 percent erucic acid, down from 30β50 percent because of the adverse health effects. While eicosenoic acid is structurally analogous, it has two fewer carbons than erucic acid; the documented cardiac concerns specifically attributed to erucic acid have not been similarly established for dietary eicosenoic acid, and no equivalent regulatory restrictions exist for C20:1 isomers.
9.5 Absence of Clinical Dosage Data
There is little research to recommend increasing or decreasing 11-eicosenoic acid intake for health benefits. No clinical trials have established a therapeutic dose, and no pharmacopoeial monograph covering eicosenoic acid as a standalone supplement was identified in the sources reviewed.
References
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