Glyceryl caprylate caprate

Glyceryl Caprylate/Caprate: A Comprehensive Reference

1. Identity, Chemical Classification, and Nomenclature

Glyceryl caprylate/caprate is the accepted INCI (International Nomenclature of Cosmetic Ingredients) name for a mixture of mono- and diglycerides derived from two medium-chain fatty acids — caprylic acid (octanoic acid, C8) and capric acid (decanoic acid, C10) — esterified with glycerol. It is formally classified as a mono-diglyceride of medium-chain fatty acids, constituting a mixture of monoacylglycerols — mainly mono-O-octanoylglycerol and mono-O-decanoylglycerol — containing variable quantities of di- and triacylglycerols.

Its chemical formula is C₂₁H₃₉O₆ and its CAS number is 91744-32-0. The IUPAC/CHEM name is "decanoic acid, mixed monoesters with glycerol and octanoic acid."

Synonyms and related designations include:

• Caprylic/capric glycerides (INCI name); mono- and di-glycerides (NF name); glycerol monocaprylocaprate; medium chain mono- & diglycerides; glycerides C8-10 mono- di- tri-; and glyceryl mono- & dicaprylo/caprate.
• Glyceryl Caprate (CAS no. 26402-22-2) is the monoester of glycerin and capric acid; Glyceryl Caprylate (CAS no. 26402-26-6) is the monoester of glycerin and caprylic acid. These individual esters are sometimes treated separately in regulatory and safety assessments but are frequently encountered in combination.
• Other names for Glyceryl Caprylate include Glyceryl Monocaprylate and Octanoic Acid, Monoester with 1,2,3-Propanetriol, and Monooctanoin.

The trade names CAPMUL MCM (NF grade) and IMWITOR 742 meet the requirements of the USP/NF under the NF monograph for "mono- and di-glycerides." The EP (European Pharmacopoeia) grade of CAPMUL MCM contains approximately 3% glycerol, whereas the NF grade contains approximately 7% glycerol.

Physical Description

Glyceryl caprylate/caprate appears as a clear or slightly yellowish liquid with low viscosity. It has an octanol-water partition coefficient (log P) of 1.21, as determined experimentally by the ASTM method, confirming its moderate lipophilicity.

2. Natural Sources and Raw Material Origins

Glyceryl caprylate/caprate is derived from a combination of medium-chain fatty acids (C8 and C10) from coconut or palm kernel oil, and glycerin, a compound naturally present in vegetable oils or obtained by fermentation.

Coconut oil contains a series of C8:0 to C18:2 fatty acids, with medium-chain fatty acids (C8:0 to C12:0) accounting for approximately 70% of the total fatty acid profile; caprylic acid (C8:0) represents approximately 6.85% and capric acid (C10:0) approximately 7.33% of total fatty acids in coconut oil.

Glyceryl caprylate/caprate is obtained by direct esterification of glycerol with caprylic (octanoic) and capric (decanoic) acids. The resulting mixture is then purified for use. Commercially, both acids are first isolated from hydrolysis of the parent vegetable oil, then combined with purified pharmaceutical- or cosmetic-grade glycerin under controlled esterification conditions. The typical composition of the resulting Glyceryl Caprylate is described as: free glycerol (1%), monoglycerides (90%), diglycerides (7%), triglycerides (1%), and water (maximum 1%).

3. Historical and Traditional Use

Glyceryl caprylate/caprate as a defined chemical entity is a product of modern industrial chemistry rather than a traditional plant-derived botanical. However, the component fatty acids — caprylic and capric acids — occur naturally in human and animal breast milk and in coconut oil, both of which have very long histories of traditional use across multiple cultures as foods and topical applications.

The first significant medical application of the glyceryl monoester form arose in the context of gallstone dissolution. Researchers at the Mayo Clinic, in collaboration with investigators at the University of Michigan College of Pharmacy, discovered that mono-octanoin was an excellent solvent for cholesterol, and learned that it was available as a commercial emulsifier (Capmul). Subsequent work showed that this compound could be infused into T-tubes and would cause gallstone dissolution in some patients.

Monooctanoin was approved by the U.S. Food and Drug Administration (FDA) on October 29, 1985, and was developed and marketed as Moctanin® by ETHITEK in the US. Monoctanoin (monocaprylin; trade name Moctanin) is a monoglyceride used to dissolve cholesterol gallstones; it was given by injection through a catheter into the bile duct, though it is no longer commercially available in the US.

Glyceryl Caprylate has been used to dissolve gallstones, representing one of the earlier formal pharmaceutical applications of this class of compound before its broader adoption as a cosmetic and pharmaceutical excipient.

In the food industry, monoglycerides of fatty acids — including those of caprylic and capric acids — have been used for many decades as emulsifiers and preservatives in commercial food processing. Their GRAS (Generally Recognized As Safe) status under US regulations reflects this established history of use. According to part 184 of the Code of Federal Regulations (CFR), the U.S. FDA has granted caprylic acid a GRAS affirmation; and according to part 172, free fatty acids (e.g., capric, caprylic) and their metallic salts are recognized as safe additives for use in food.

4. Key Constituents and Active Compounds

Glyceryl caprylate/caprate is itself an active ingredient rather than a complex botanical extract, so its key constituents are the component molecules it contains:

• Monoglycerides (primarily): It is a mono-diglyceride of medium-chain fatty acids (mainly caprylic and capric), constituting a mixture of monoacylglycerols — mainly mono-O-octanoylglycerol and mono-O-decanoylglycerol — with variable quantities of di- and triacylglycerols.
• Caprylic acid (C8:0, octanoic acid): An 8-carbon, saturated, medium-chain fatty acid. Caprylic acid is naturally present in breast milk, bovine milk, and coconut oil.
• Capric acid (C10:0, decanoic acid): Decanoic acid is a medium-chain fatty acid with 10 carbons (CH₃(CH₂)₈COOH). Capric acid is widely present in coconut and palm kernel oils.
• Glycerol backbone: A trihydric alcohol that naturally forms the structural backbone of all glycerides.

5. Mechanisms of Action

5.1 Antimicrobial Activity

Antimicrobial lipids such as fatty acids and monoglycerides are promising antibacterial agents that destabilize bacterial cell membranes, causing a wide range of direct and indirect inhibitory effects.

The primary proposed mechanism involves membrane disruption. The widely recognized mode of action is that the hydroxyl group in the monoglyceride is adsorbed to the polar part of the cell membrane surface, with the acyl carbon chain inserting into the hydrophobic region of the membrane, then moving across the phospholipid bilayers driven by hydrophobic interaction, resulting in cell membrane perforation and eventual cell death.

In general, monoglycerides have lower minimum inhibitory concentrations (MICs) than fatty acid equivalents against different bacteria, suggesting that the glycerol ester form may confer enhanced antimicrobial potency relative to the free fatty acid.

Regarding selectivity between gram-positive and gram-negative bacteria: Capric acid and its monoglyceride derivative, monocaprin, have saturated hydrocarbon chains that are 10 carbons long, and also have high antibacterial activity, especially against gram-negative bacteria that are commonly associated with foodborne infections such as Campylobacter jejuni.

With respect to antifungal action: Scientific evidence suggests that glyceryl caprylate, as well as its related MCFAs, possess mild antimicrobial properties, including activity against certain fungal species such as Malassezia and Candida. The antifungal effects are attributed to the ability of medium-chain fatty acids to disrupt the lipid membranes of fungi, thereby inhibiting their growth or viability.

5.2 Emulsification and Solubilization

As a functional lipid excipient, glyceryl caprylate/caprate acts as a solubilizer and emulsifier in oral, topical, transdermal, and parenteral drug delivery systems. Studies using phase diagrams have demonstrated that the monoglyceride form yields microemulsion (clear or translucent liquid) and emulsion phases, whereas di- and triglycerides exhibit an additional gel phase, suggesting that the monoglyceride's amphiphilic character and HLB value make it particularly effective at forming thermodynamically stable emulsions and microemulsions.

5.3 Skin Penetration Enhancement

Studies have tested the skin penetration enhancing effects of a series of ingredients used in topical pharmaceutical and cosmetic formulations, including glyceryl monocaprylate/caprate among predominantly fatty acid esters. The enhancement by monoglycerides and caprylic acid esters has been evaluated and compared with the enhancement effects of free fatty acids; it was found that free fatty acids mainly affected drug diffusion, while monoglycerides affected the partition. Enhancement was marked in the case of glyceryl monocaprylate. A linear relationship between the flux of the model drug papaverine hydrochloride and the amount of enhancer in skin was established.

5.4 Digestion and Metabolism of the Ester Bond

When ingested, glyceryl caprylate/caprate is subject to the normal processes of triglyceride digestion. Triglyceride digestion begins in the intestinal tract, where the triglyceride is hydrolyzed first to an α,β-diglyceride, then to a β-monoglyceride. These hydrolytic reactions occur at an oil-water interface. Approximately 28% of the β-monoglyceride is isomerized to α-monoglyceride, and approximately 75% of the α-monoglyceride is further hydrolyzed to free glycerol. Free glycerol enters the intestinal wall independently of the lipids; the free fatty acids and glycerol are then available for the resynthesis of triglycerides.

The liberated medium-chain fatty acids have a distinctive metabolic routing: medium-chain fatty acids (MCFAs) have a unique advantage over long-chain fatty acids in that they are absorbed more rapidly and transported directly from the intestines to the liver via the portal vein. Unlike long-chain fatty acids, which require carrier proteins for transportation, MCFAs diffuse freely across cell membranes and are readily available for energy production while being less likely to be stored as adipose tissue.

6. Scientific Evidence by Area of Use

6.1 Antimicrobial Activity — Bacteria

Evidence type: In vitro and animal studies; limited human/clinical evidence specific to the glyceryl ester form.

A variety of free fatty acids and their monoglycerides have been reported to exert antimicrobial activity against a wide range of microorganisms. One study examined the efficacy of caprylic acid and its monoglyceride, monocaprylin, against common mastitis pathogens including Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus, and Escherichia coli. Milk samples containing 50 mM or 100 mM caprylic acid, and 25 mM or 50 mM monocaprylin, were inoculated separately with a 3-isolate mixture of each of the 5 pathogens and incubated at 39°C. Caprylic acid and its monoglyceride, monocaprylin, were found to be effective in inactivating infant pathogens such as herpes simplex virus, respiratory syncytial virus, Haemophilus influenzae, and Group B streptococci.

Of 11 fatty acids and monoglycerides tested against Campylobacter jejuni, the 1-monoglyceride of capric acid (monocaprin) was the most active in killing the bacterium. Of the fatty acids tested, capric acid was the most active in killing the bacteria, reducing the bacterial count by ≥6.8 log₁₀ in 10 minutes. Monocaprin (MC) was the most active of the monoglycerides, also reducing the bacterial count by ≥6.8 log₁₀.

In cosmetic preservation studies, evaluation of the preservative activities of glyceryl caprylate 1-monoglyceride in cosmetic formulations found that it has very excellent preservative activity against bacteria, but less activity against fungi. The antimicrobial activity of glyceryl caprylate was found to be improved under acidic conditions in formulation.

Evidence strength: The preponderance of antimicrobial evidence for glyceryl caprylate/caprate is derived from in vitro studies and, to a lesser extent, animal models. The evidence base is limited primarily to in vitro studies and data extrapolated from the action of pure caprylic and capric acids, rather than the glyceryl esters specifically. There are few, if any, clinical studies directly assessing the efficacy of glyceryl caprylate caprate as a primary or adjunctive treatment for infections in humans. Evidence is therefore classified as preliminary and in vitro/preclinical only for the ester mixture itself.

6.2 Cosmetic Preservation

Evidence type: In vitro challenge testing; regulatory assessment.

Glyceryl caprylate is known as a multifunctional ingredient that acts as a natural preservative, emollient, emulsifier, and skin penetration enhancer. The substance has a good effect on numerous bacteria, yeasts, and molds. Its use as a cosmetic preservative booster is well-established in cosmetic formulation science, where it is employed at concentrations typically between 0.5% and 5% to reduce reliance on conventional synthetic preservatives. Optimal combinations of glyceryl caprylate with other antimicrobial agents have been identified in formulation studies; among those tested, methylparaben showed the highest preservative activity in combination with glyceryl caprylate.

6.3 Gallstone Dissolution (Historical Pharmaceutical Use)

Evidence type: Clinical studies; FDA-approved application (now withdrawn from market).

Complete gallstone dissolution occurred in approximately 50–75% of patients receiving monooctanoin. Although mechanical stone removal is still considered to be the treatment of choice for retained gallstones, monooctanoin use appeared promising for stone dissolution in patients in whom mechanical removal has been unsuccessful or is impossible. Monooctanoin has a relatively high viscosity and dissolves gallstones very slowly, which was noted as a practical limitation. Gastrointestinal side effects such as anorexia, nausea, vomiting, diarrhea, and abdominal pain were reported most commonly. The product has since been withdrawn from the US market.

6.4 Pharmaceutical Drug Delivery (Bioavailability Enhancement)

Evidence type: In vitro phase diagram and solubility studies; formulation research.

As functional lipid excipients, CAPMUL-type medium-chain mono- and diglycerides act as solubilizers and emulsifiers in oral, topical, transdermal, and parenteral drug delivery systems. These excipients are recognized as the ideal starting point when formulating BCS Class II (poorly water-soluble) and BCS Class IV (poorly permeable) molecules.

A study published in Pharmaceutical Research compared physiochemical properties of mono-, di-, and triglycerides of medium-chain fatty acids for development of oral pharmaceutical dosage forms of poorly water-soluble drugs. Phase diagrams were prepared using a monoglyceride (glycerol monocaprylocaprate: Capmul MCM® EP), a diglyceride (glycerol dicaprylate), and two triglycerides (glycerol tricaprylate: Captex 8000®; caprylic/capric triglycerides: Captex 355 EP/NF®) in combination with a common surfactant (PEG-35 castor oil: Cremophor EL®) and water. The monoglyceride gave microemulsion (clear or translucent liquid) and emulsion phases, whereas di- and triglycerides exhibited an additional gel phase.

The mixture of medium-chain triglycerides and medium-chain mono/diglycerides is considered important for the bioavailability of active ingredients in liquid-filled hard gel capsule formulations. Pharmaceutical formulations using this approach have employed approximately 5% to 25% by weight medium-chain mono/diglycerides.

Evidence strength: Evidence for the drug-delivery excipient role is well-supported by formulation science and in vitro studies; head-to-head clinical bioavailability comparisons specific to glyceryl caprylate/caprate versus other excipients in humans are limited in the published literature.

6.5 Skin Penetration Enhancement (Topical Applications)

Evidence type: In vitro skin penetration studies (ex vivo human/porcine skin models).

A 1998 study in the International Journal of Pharmaceutics tested the skin penetration enhancing effects of 11 excipients including glyceryl monocaprylate/caprate across a range of fatty acid ester types. The skin penetration enhancing effects of a series of 11 ingredients used in topical pharmaceutical and cosmetic formulations were tested; the excipients tested were predominantly fatty acid esters including glyceryl monocaprylate/caprate, isopropyl myristate, decyl oleate, glyceryl tricaprylate/caprate, and others. It was shown that free fatty acids mainly affected the diffusion of the drug, and the monoglycerides affected the partition. Enhancement was marked in the case of glyceryl monocaprylate, with a linear relationship established between the flux of papaverine hydrochloride and the amount of enhancer in skin.

Evidence strength: Skin penetration enhancement is supported by in vitro and ex vivo data, which are meaningful in formulation science but do not constitute human clinical evidence of therapeutic efficacy.

6.6 Gut Microbiome and Intestinal Health (Preclinical)

Evidence type: Animal studies.

It has been reported that MCFAs and monoglycerides can improve immune health-related parameters, motivating deeper investigation of the mechanistic underpinnings. Studies of 0.5% capric acid in miniature pigs found that it protected against cyclophosphamide-induced intestinal inflammation, oxidative stress, and gut barrier dysfunction, tempering inflammatory cytokine production while aiding intestinal barrier function in vivo.

This body of work pertains primarily to the free fatty acid forms and to animal models, not to the glyceryl ester form specifically tested in humans.

6.7 Lipid Metabolism and Cholesterol Effects (Preclinical)

Evidence type: Animal studies.

A study in C57BL/6J mice investigated the effects of medium-chain triglycerides/MCFAs on bile acid reabsorption. Mice in a cholesterol-rich medium-chain triglyceride diet group exhibited lower body weights and serum total cholesterol and LDL-C levels, and a higher HDL-C/LDL-C ratio, compared with a cholesterol-rich long-chain triglyceride diet group. C8:0 and C10:0 decreased the permeability of cholic acid in Caco-2 cell monolayers, and MCT/MCFAs inhibited ileal bile acid-binding protein (I-BABP) gene expression in the small intestines and Caco-2 cells.

Evidence strength: Animal data only. No human clinical trials specifically using glyceryl caprylate/caprate as the test agent for lipid-lowering outcomes have been identified in the available literature.

7. Body Systems and Health Areas of Association

• Skin and integumentary system: Glyceryl monoesters are used mostly as skin-conditioning agents — emollients and/or surfactant-emulsifying agents — in cosmetics. They contribute to barrier support, moisturization, and texture improvement, and exert antimicrobial effects relevant to skin health.
• Gastrointestinal system: The compound has been used medically for cholesterol gallstone dissolution and is metabolized via normal lipid digestion pathways. After absorption, the liberated MCFAs are transported directly from the intestines to the liver via the portal vein, diffusing freely across cell membranes without requiring carrier proteins.
• Hepatobiliary system: Historical pharmaceutical use targeted the biliary tract for cholesterol gallstone dissolution.
• Immune/microbial defense: Free fatty acids and their monoglycerides have been found to be inhibitory towards an array of pathogenic microorganisms including enveloped viruses, and gram-positive and gram-negative bacteria.
• Pharmaceutical delivery (transdermal and oral): Acts as a solubilizer and bioavailability enhancer for poorly soluble drugs, relevant to systemic drug delivery.

8. Dosage Forms and Reported Dosages

Glyceryl caprylate/caprate is employed in several distinct application contexts, each with characteristic concentration ranges derived from published data and regulatory submissions:

• Cosmetic and personal care formulations (topical): The ingredient is well tolerated by the skin and is safe for use within the recommended concentrations of 0.5–5%.
• Cosmetic preservative function (topical): Used as a preservative booster or natural multifunctional in cosmetic formulations, typically within the 0.5–5% range referenced above.
• Pharmaceutical oral lipid-based formulations: Pharmaceutical formulations have employed approximately 5% to 25% by weight medium-chain mono/diglycerides, or from approximately 5% to 15% by weight medium-chain mono/diglycerides. In exemplary formulations, amounts of approximately 20 mg to 50 mg, or approximately 25 mg to 30 mg, of medium-chain mono/diglycerides per dosage unit have been described.
• Gallstone dissolution (historical, medical use): Monooctanoin was given by injection through a catheter into the bile duct — a route of administration that is unrelated to dietary supplementation and that required medical supervision.

No standardized oral dietary supplement dosage for glyceryl caprylate/caprate as such has been established in the peer-reviewed clinical literature identified in this review.

9. Safety Considerations

9.1 Regulatory Safety Status

Based on available data, the Cosmetic Ingredient Review (CIR) Expert Panel found that glyceryl monoesters — including Glyceryl Caprylate and Glyceryl Caprylate/Caprate — are safe as cosmetic ingredients in the present practices of use and concentration.

According to part 184 of the Code of Federal Regulations, the U.S. FDA has granted caprylic acid (the principal fatty acid component) GRAS affirmation. Caprylic acid is reported in the Merck Index to have an oral LD₅₀ (rats) of 10.08 g/kg, which is essentially nontoxic by that measure.

The CIR Expert Panel concluded that the glyceryl monoesters in its re-review are safe as cosmetic ingredients in the present practices of use and concentration. In January 2025, an extensive search of the world's literature was performed for studies dated 1999 forward as part of a re-review process, indicating ongoing regulatory monitoring of this ingredient class.

9.2 Skin Irritation and Sensitization

Glyceryl caprylate (15%) did not induce skin irritation or sensitization in a repeated insult patch test (RIPT) involving 63 healthy subjects, 58 of whom completed the study. In a separate CIR-reviewed study, Glyceryl Caprylate (15%) did not induce skin irritation or sensitization in a repeated insult patch test (RIPT) involving 63 healthy subjects.

9.3 Gastrointestinal Effects (from Medical Use)

When administered directly into the bile duct at concentrations relevant to gallstone dissolution, gastrointestinal side effects such as anorexia, nausea, vomiting, diarrhea, and abdominal pain were reported most commonly. The most common adverse effects of biliary administration were abdominal or stomach pain, usually mild, or a burning sensation. These effects are associated with a high-dose, direct-instillation medical use that is not representative of topical or low-dose oral supplement use.

9.4 Metabolic Considerations

The safety of human dietary consumption of MCT (which liberates caprylic and capric acids upon digestion), up to levels of 1 g/kg, has been confirmed in clinical trials.

No evidence of pro-oxidant behavior of glyceryl caprylate could be found in oxidation studies of cosmetic emulsions, which is relevant to product stability and potential for generating lipid oxidation products on skin.

9.5 Potential Interactions and Special Populations

No specific drug–drug or drug–supplement interactions with glyceryl caprylate/caprate have been identified in the peer-reviewed literature reviewed here. However, given its established role as a pharmaceutical bioavailability enhancer and skin penetration enhancer, its presence in formulations containing active pharmaceutical ingredients may influence the absorption rate of co-administered or co-formulated compounds.

Glyceryl caprylate/caprate is generally well tolerated, but hypersensitivity to fatty acids or glycerin, though very rare, can cause redness or itching.

9.6 Environmental and Physical Safety

Glyceryl caprylate/caprate is non-comedogenic and biodegradable, rendering it suitable for sensitive skin and environmentally friendly product formulations.

References

• PubChem: Glyceryl Caprylate Caprate — Compound Summary
• Cosmetic Ingredient Review (CIR): Final Report of the Amended Safety Assessment of Glyceryl Monoesters (International Journal of Toxicology, 2004)
• CIR: Safety Assessment of Monoglyceryl Monoesters as Used in Cosmetics (International Journal of Toxicology, 2020, Supplement)
• CIR: Re-Review Safety Assessment of Glyceryl Monoesters (2025)
• US Patent 11,641,856: Synergistic Antibacterial Activity of Medium Polarity Oils in Combination with Antibacterial Agents on Bacterial Biofilms
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• Glyceryl Caprylate/Caprate — SpecialChem Cosmetics INCI