IngredientsElenolic acid (also rendered as elenolate in the context of its salt forms) is a nonphenolic compound whose derivatives and analogues constitute the iridoid part of the most important olive secondary metabolites. More specifically, iridoids and secoiridoids are compounds that are usually glycosidically bound and are produced from the secondary metabolism of terpenes; the secoiridoids in Oleaceae are usually derived from the oleoside type of glucosides, which are characterized by an exocyclic 8,9-olefinic functionality, a combination of elenolic acid and a glucosidic residue.
The CAS registry number for elenolic acid is 34422-12-3, its molecular formula is C11H14O6 and its molecular weight is 242.23 g/mol. Structurally, elenolic acid contains a carboxylic acid group and hydroxyl groups, contributing to its antioxidant and bioactive properties.
Elenolic acid is a secoiridoid compound naturally found in olives (Olea europaea), olive leaves, and extra virgin olive oil. Elenolic acid is a component of olive oil and olive leaf extract (OLE); it can be considered a marker for maturation of olives.
Oleuropein — the parent compound from which elenolic acid is derived — is most abundant in young olive drupes, reaching concentrations up to 140 mg/g dry weight, and in leaves at 60–90 mg/g dry weight, though levels decline during fruit maturation and processing into oil. Olive phenolics are much more concentrated in the leaves compared with olive oil or fruit: 1,450 mg total phenolics per 100 grams fresh leaf versus 110 mg per 100 grams of fruit and 23 mg per 100 mL in extra virgin olive oil.
Elenolic acid is not found in isolation at high abundance in raw plant material; it arises primarily through enzymatic or chemical hydrolysis of oleuropein and related secoiridoids. Oleuropein glycoside, aglycone, and elenolic acid are derived from the hydrolysis of oleuropein, as well as from the aglycones of ligstroside and oleuropein. For elenolic acid forms (elenolic acid and decarboxymethyl elenolic acid), the content follows that of oleuropein and ligstroside derivatives; these compounds derive from oleosides methyl ester and so from oleuropein and ligstroside by chemical and/or enzymatic hydrolysis.
Elenolic acid is also present in other members of the Oleaceae family. Oleuropein is also present in other plants of the Oleaceae family, such as Ligustrum species. Elenolic acid is a subunit of oleuropein, a bitter chemical compound found in olives and the leaves of the olive tree, alongside closely related compounds such as 10-hydroxyoleuropein, ligstroside, and 10-hydroxyligstroside, which are tyrosol esters.
Chemically, oleuropein is the ester of elenolic acid and 3,4-dihydroxyphenyl ethanol (hydroxytyrosol), which possesses beneficial effects on human health, such as antioxidant, antiatherogenic, anti-cancer, anti-inflammatory, and antimicrobial properties. The major phenolic compound in the olive fruit is oleuropein, which exists in quantities as much as 14% in dried fruit, and is an ester comprised of hydroxytyrosol and elenolic acid.
Oleuropein is converted to both the dextrorotary and levorotary forms of elenolic acid by the enzymes esterase and beta-glucosidase, which are found in olive trees as well as human blood. The dextrorotary form of elenolic acid does not bind to human blood cells, but the levorotary form of elenolic acid does bind to human blood cells; when the levorotary elenolic acid binds to human blood cells, it becomes ineffective but does not appear to cause negative side effects. In the gut, oleuropein resists degradation in the upper gastrointestinal tract and the small intestine, and thus at least a portion of a dose of oleuropein reaches the colon, where microflora can perform bioconversion; deglycosylation converts oleuropein to oleuropein aglycone, and subsequent hydrolysis by esterase forms elenolic acid (as well as hydroxytyrosol acetate).
The biosynthesis of oleuropein in Oleaceae proceeds via a branching in the mevalonic acid pathway from secondary metabolism, resulting in the formation of oleosides, from which secoiridoids are derived. During ripening, while elenolic acid glucoside and demethyloleuropein accumulate in olive fruits, oleuropein levels decrease; oleuropein biodegradation into these glycosylated derivatives involves cleavage by specific endogenous esterases, through hydrolysis of the hydroxytyrosol ester or methyl ester, respectively, while activation of endogenous β-glucosidase during crushing or malaxation produces the aglycone forms by cleavage of glucose.
Elenolic acid is encountered in research and supplementation in the following forms:
Critically, calcium elenolate has been shown to have virucidal activity against influenza A virus in vitro; however, given that elenolic acid is at levels hard to detect in olive leaf extract, the relevance of this result for the whole extract is uncertain.
Elenolic acid itself was not isolated or named as a distinct compound until the twentieth century, but its primary botanical source — the olive tree and its leaves — has a history of medicinal use spanning millennia. Olive (Olea europaea L.) has been used traditionally as a medicinal plant with different indications in various preparations derived from its leaves, fruits, seeds, wood, bark, and oil; it has been part of the traditional human and veterinary pharmacopeia in Mediterranean countries.
The olive was native to Asia Minor and spread from Iran, Syria, and Palestine to the rest of the Mediterranean basin approximately 6,000 years ago. The olive tree was cultivated in Crete, where the leaves were used to clean wounds as early as 3500 BC.
Olive leaves have traditionally been brewed as an herbal tea in the Mediterranean and used in traditional medicine as a supposed treatment for fever and malaria. Medicinal use of olive leaf extract dates back to the early 1800s, when it was used in liquid form as a treatment for malarial infections.
Oleuropein is the main glycoside in olives and is responsible for the bitter taste of immature and unprocessed olives. The bitterness of fresh olive-leaf tea or unprocessed olive products is attributable in large part to this parent compound, which breaks down to yield elenolic acid. When consumed, olive leaves have a sharp bitter taste; when infused as a tea, the intensity is moderated but maintains an astringent flavor due to high levels of polyphenols and organic acids.
Olive is an ancient, cultivated botanical used as both food and medicine; olive leaf is primarily used in modern herbalism for conditions of the cardiovascular, immune, and urinary systems.
In 1969, a Dutch researcher determined the active ingredient in oleuropein to be a substance called elenolic acid. Elenolic acid was found to have powerful antibacterial properties; by the late 1960s, research by scientists at Upjohn showed that elenolic acid also slowed the growth of viruses, and it was found to inhibit a variety of viruses associated with the common cold in humans.
Elenolic acid, a nonphenolic compound, and its derivatives and analogues constitute the iridoid part of the most important olive secondary metabolites. Elenolic acid, a nonphenolic compound, and its derivatives and analogues constitute the iridoid part of the most important olive secondary metabolites; their presence in olive samples indicates complex transformations that take place during olive fruit maturation and processing. Oleuropein is a major constituent of the secoiridoids group, which is an ester of hydroxytyrosol and the elenolic acid glucoside.
Several biologically active compounds are esters or conjugates of elenolic acid:
Four major phenolic compounds present in olive oil — hydroxytyrosol, oleuropein, hydroxytyrosol-elenolate, and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde — were studied for their protective effect on red blood cells against oxidative damage, and all four compounds significantly showed the protective effect in a dose-dependent manner.
Both elenolic acid and hydroxytyrosol are potent antioxidants and radical scavengers, and the phenolic components in olive oil are believed to play a vital role in the prevention of coronary artery disease and atherosclerosis. Minor phenolic constituents have been shown to possess antioxidant, anti-inflammatory, and anti-thrombotic activity.
The most mechanistically detailed work on elenolic acid's direct biological activity concerns its effects on enteroendocrine L-cells of the gut. Elenolic acid dose-dependently stimulates GLP-1 (glucagon-like peptide-1) secretion in mouse clonal L-cells and isolated mouse ileum crypts; in addition, elenolic acid induces L-cells to secrete peptide YY (PYY).
Elenolic acid induces a rapid increase in intracellular calcium [Ca²⁺]ᵢ and the production of inositol trisphosphate in L-cells, indicating that elenolic acid activates phospholipase C (PLC)-mediated signaling; consistently, inhibition of PLC or Gαq ablates elenolic acid-stimulated increase of [Ca²⁺]ᵢ and GLP-1 secretion.
In the presence of vildagliptin, elenolic acid-stimulated GLP-1 release was further increased; vildagliptin was confirmed to be potent in inhibiting DPP-IV, while elenolic acid at the same doses was inactive, demonstrating that elenolic acid's action on GLP-1 secretion from L-cells is mediated via a DPP-IV-independent mechanism.
Earlier studies showed antiviral effects of elenolic acid salts against several enveloped and non-enveloped viruses; however, the antiviral mechanism of action of elenolic acid remains unknown. It has been stipulated that elenolic acid salts interfere with the virus life cycle and, in the case of retroviruses, with the inhibition of reverse transcriptase and protease; more recently, some studies indicated neuraminidase inhibition as a possible mechanism of action of elenolic acid derivatives.
Among the identified compounds in olive brines, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol showed the strongest anti-lactic acid bacteria activity and its presence in olive brines explained the growth inhibition of these bacteria during fermentation of olives.
Cardioprotective effects occur by many mechanisms including endothelial activation and inhibition of platelet aggregation, prevention of low-density lipid oxidation, and modulation of arachidonic acid metabolism. These effects are attributed to the phenolic fraction as a whole, within which elenolic acid constituents participate.
The most intensive and recent research on elenolic acid as a direct pharmacological agent — distinct from the whole olive leaf extract — has focused on metabolic disease. A 2022 study published in Frontiers in Nutrition (Wang et al., Virginia Tech) investigated elenolic acid's effects on gut hormone release and metabolic outcomes in diet-induced obese (DIO) mice.
In vivo, a single dose of elenolic acid acutely stimulated GLP-1 and PYY secretion in mice, accompanied by improved glucose tolerance and insulin levels; oral administration of elenolic acid at a dose of 50 mg/kg/day for 2 weeks normalized fasting blood glucose and restored glucose tolerance in high-fat diet-induced obese mice to levels comparable to chow-fed mice; elenolic acid also suppressed appetite, reduced food intake, promoted weight loss, and reversed perturbed metabolic variables in obese mice.
Acute administration of elenolic acid increased blood GLP-1 and PYY levels by about 50% (p < 0.05), demonstrating that elenolic acid-evoked GLP-1 and PYY secretion from L-cells ex vivo is recapitulated in vivo.
A subsequent study compared elenolic acid to established pharmaceutical agents in a mouse model of type 2 diabetes. After just one week, obese mice with diabetes that were given oral elenolic acid weighed significantly less and showed better blood sugar regulation than before treatment and compared to control obese mice; the glucose-lowering effect was comparable to that of the injectable diabetic medication liraglutide and better than metformin, one of the most common oral medicines for type 2 diabetes. After four to five weeks of treatment, the mice showed a 10.7% reduction in obesity as well as blood sugar levels and insulin sensitivity that were comparable to those of healthy lean mice; elenolic acid also significantly reduced food intake and promoted weight loss, associated with improved circulating levels of PYY and GLP-1 and the downregulation of agouti-related peptide in the hypothalamus.
Elenolic acid increases circulating GLP-1, PYY, and GIP levels in DIO mice; lowers blood glucose in db/db mice, matching liraglutide and outperforming metformin; and suppresses appetite and delays gastric emptying.
All current evidence is from animal (mouse) models and cell-based (in vitro) experiments. No human clinical trials on elenolic acid as an isolated compound for obesity or type 2 diabetes have been published to date. These results suggest that elenolic acid could be a dual-action agent as an alternative or adjuvant treatment for both type 2 diabetes and obesity, but this remains a hypothesis to be tested in human studies. Extrapolation from mouse studies to humans requires caution.
The antiviral properties of elenolic acid's salt form, calcium elenolate, were first systematically investigated by H.E. Renis and M. Soret at the Upjohn Company in 1969. It is hypothesized that the real antimicrobial effect of oleuropein is due to its components hydroxytyrosol and elenolic acid, although there are still no studies carried out with elenolic acid obtained from natural sources; early research with calcium elenolate salts revealed its antiviral activity, including against influenza and parainfluenza. The anti-influenza effect of elenolic acid-rich extracts can be attributed to elenolic acid content because the extract showed an elenolic acid dose-dependent inhibition; the role of several elenolic derivatives against influenza viruses has been known for decades, especially in works done with the calcium salt of elenolic acid.
A patent filed in 1973 claimed the use of elenolic derivatives as an anti-influenza drug; the patent described an in vivo animal model in which calcium elenolate administered intranasally reduced virus infection and accelerated its eradication in the lungs.
A 2021 peer-reviewed study published in Antiviral Chemistry & Chemotherapy (Salamanca et al.) tested Isenolic®, a standardized olive leaf extract characterized by HPLC for its elenolic acid content, against influenza virus in vitro. The aim of this study was to test the anti-influenza activity of a standardized olive leaf extract rich in elenolic acid compared to oseltamivir; the extract demonstrated neuraminidase inhibitor activity higher than the 4% formulation and preserved cell viability under viral infection. Experiments were conducted using sialic acid-overexpressing Madin-Darby Canine Kidney (MDCK-SIAT1) cells.
The antiviral evidence for elenolic acid is limited to in vitro cell studies and historical animal model experiments, primarily conducted with the calcium salt form. No human clinical trials have investigated elenolic acid for antiviral purposes. Calcium elenolate has been shown to have virucidal activity against influenza A virus in vitro; however, given that elenolic acid is at levels hard to detect in olive leaf extract, the relevance of this result for the whole extract is uncertain.
Elenolic acid has shown antibacterial actions against several species of Lactobacilli and Staphylococcus aureus. Elenolic acid has shown antibacterial actions against several species of Lactobacilli, Staphylococcus aureus, and Bacillus subtilis in test tube studies; whether the oleuropein in the leaf undergoes such transformation in vivo is open to question, raising some question as to its antibacterial effects and potential use for this purpose in humans.
Calcium elenolate, an antiviral agent which inhibits reverse transcriptases, inhibits the growth of chicken embryo fibroblast cells as well as Escherichia coli and Bacillus subtilis strains.
Antibacterial evidence for elenolic acid is confined to in vitro studies. There are no human clinical trials examining antibacterial efficacy.
Human clinical research on elenolic acid's cardiovascular effects has been conducted primarily in the context of whole olive leaf extract (OLE), which contains elenolic acid among multiple other phenolic compounds. Attributing observed effects exclusively to elenolic acid is therefore not possible from these studies.
A 2016 randomized, double-blind, controlled, crossover trial by Lockyer et al. (published in European Journal of Nutrition) investigated phenolic-rich OLE in pre-hypertensive males. The trial investigated the effects of a phenolic-rich olive leaf extract on blood pressure; 60 pre-hypertensive males consumed either OLE (136 mg oleuropein; 6 mg hydroxytyrosol) or a polyphenol-free control daily for 6 weeks before switching to the alternate arm after a 4-week washout. Daytime and 24-h systolic blood pressure and daytime and 24-h diastolic blood pressure were all significantly lower following OLE intake relative to the control. These data support previous research suggesting that OLE intake engenders hypotensive and lipid-lowering effects in vivo.
A meta-analysis on the antihypertensive effect of OLE confirmed: the meta-analysis showed a significant reduction effect of OLE on systolic blood pressure.
Human clinical evidence for cardiovascular benefits exists for phenolic-rich olive leaf extract, not for isolated elenolic acid. The specific contribution of elenolic acid within such extracts has not been experimentally separated from that of oleuropein, hydroxytyrosol, or other co-occurring phenolics.
3,4-DHPEA-EDA (the dialdehydic form of hydroxytyrosol-elenolic acid) plays an important protective role against reactive oxygen species-induced oxidative injury in red blood cells, and this effect is more potent than that evidenced by hydroxytyrosol or oleuropein. This was demonstrated in an in vitro study examining olive oil polyphenols at physiological concentrations. The addition of phenolic compounds at 20 and 10 µM did not produce further protection compared with ascorbic acid alone, except for 3,4-DHPEA-EDA; this compound was shown to produce further protection even at 5 µM.
These findings are from in vitro cell and blood studies only. The relevance to in vivo human antioxidant protection has not been established in clinical trials.
Based on published research, elenolic acid and its closely related derivatives have been investigated or associated with the following body systems and health areas:
No established human dosage for isolated elenolic acid exists. All dosages reported below are from preclinical (animal) research or are expressed as part of extract formulations in human trials. The following are stated as reported in cited sources:
A pharmacokinetically relevant finding is the stereospecific binding behaviour of elenolic acid's enantiomers: the dextrorotary form of elenolic acid does not bind to human blood cells, but the levorotary form does bind to human blood cells; when the levorotary elenolic acid binds to human blood cells, it becomes ineffective but does not appear to cause negative side effects. This observation, derived from patent literature citing work with calcium elenolate preparations, may have implications for the bioavailability and effective circulating concentration of the compound.
Because elenolic acid is derived from oleuropein, and because whole olive leaf extracts containing oleuropein and related secoiridoids have demonstrated significant blood pressure-lowering effects in human trials, individuals taking antihypertensive medications may be at risk of additive hypotensive effects when consuming high-dose OLE or elenolic acid-rich preparations. Daytime and 24-h systolic and diastolic blood pressure were all significantly lower following OLE intake relative to the control in a randomized trial in pre-hypertensive males.
Given its potent ability to stimulate GLP-1 and PYY secretion and lower blood glucose in animal models, elenolic acid has the theoretical potential to enhance the blood glucose-lowering effects of antidiabetic medications. The glucose-lowering effect of oral elenolic acid in obese diabetic mice was comparable with that of the injectable diabetic medication liraglutide and better than metformin. This pharmacodynamic activity warrants attention in any concurrent use with insulin, sulfonylureas, or GLP-1 receptor agonists, though no human interaction data exist.
In vitro studies have demonstrated that oleuropein inactivates androstenedione 6-hydroxylase (CYP3A4) activity in human liver microsomes. Since elenolic acid is a direct hydrolysis product of oleuropein, preparations that deliver both compounds — as found in standardized OLE supplements — may affect CYP3A4-mediated drug metabolism, though this has not been confirmed for elenolic acid in isolation.
The protective effects of olive leaf extract on genotoxicity and oxidative damage in cultured human blood cells have been studied; the olive leaf extract at all doses did not induce any significant changes in genotoxicity, and it increased total antioxidant capacity in plasma in vitro. These data concern whole OLE and cannot be attributed specifically to elenolic acid.
No dedicated human clinical safety trials have been conducted on isolated elenolic acid. The existing animal data suggests the compound is tolerated at the doses studied; however, no established human-equivalent safe dose, tolerable upper limit, or formal toxicology profile for isolated elenolic acid has been published in peer-reviewed literature accessible to this review. All available safety data for related preparations pertains to whole olive leaf extract or oleuropein-rich fractions.
Elenolic acid remains an emerging research compound. Elenolic acid acts as a multi-target agent for obesity and type 2 diabetes management; obesity and type 2 diabetes are among the most common metabolic diseases globally; elenolic acid, derived from olives, was shown to possess potent acute effects on obesity and diabetes associated with increased gut hormone secretion, and researchers continue to investigate its long-term effects in multiple mouse models.
Key gaps include: the absence of human pharmacokinetic data for isolated elenolic acid; no human clinical trials for any indication; an incompletely characterized antiviral mechanism of action; and limited understanding of how food processing conditions (heating, alkaline treatment, fermentation) alter the absolute quantity of elenolic acid available for absorption from dietary sources.
It is hypothesized that the real antimicrobial effect of oleuropein would be due to its components hydroxytyrosol and elenolic acid, although there are still no studies carried out with elenolic acid obtained from natural sources. This represents a significant and acknowledged gap in the field as of the most recent literature.
Health conditions that Elenolic acid may help support.
Body systems that Elenolic acid may help support.
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