Caprylic acid (octanoic acid) is a linear medium-chain fatty acid, found in coconut, goat's milk, and breast milk.

Industrially it appears as a colourless to yellowish liquid.

What it is used for and where

Medical

Phytochemical analysis found monoglycerides and monocaprilin effective against herpes simplex virus, Haemophilus influenzae, respiratory syncytial virus, group B streptococci (1).

It has also been reported as a bactericide against Campylobacter jejuni, a bacterium that causes avian diseases, as an antioxidant (2) and also has potential in anti-aging applications, Alzheimer's, infections.

Cosmetics

Cleansing agent. Ingredient that cleanses skin without exploiting the surface-active properties that produce a lowering of the surface tension of the stratum corneum. 

Fragrance. It plays a very important role in the formulation of cosmetic products as it allows perfume to be enhanced, masked or added to the final product, improving its commercial viability.  The consumer always expects to find a pleasant scent in a cosmetic product.

Surfactant - Cleansing agent. Cosmetic products used to cleanse the skin utilise the surface-active action that produces a lowering of the surface tension of the stratum corneum, facilitating the removal of dirt and impurities. 

Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable and are used to soothe or soften the skin and emulsify, so they need a specific, stabilising ingredient. This ingredient forms a film, lowers the surface tension and makes two immiscible liquids miscible. A very important factor affecting the stability of the emulsion is the amount of the emulsifying agent. Emulsifiers have the property of reducing the oil/water or water/oil interfacial tension, improving the stability of the emulsion and also directly influencing the stability, sensory properties and surface tension of sunscreens by modulating the filmometric performance.

Food

FDA-approved substance generally recognised as safe (GRAS).

Caprylic acid studies

Molecular Formula   C₈H₁₆O₂

Molecular Weight      144.21

CAS  124-07-2

UNII    OBL58JN025

EC Number  204-677-5

Synonyms:

• octanoic acid
• 1-heptanecarboxylic acid
• n-octanoic acid
• n-caprylic acid
• Octylic acid

References______________________________________________________________________

(1) Isaacs, C. E., Litov, R. E., & Thormar, H. (1995). Antimicrobial activity of lipids added to human milk, infant formula, and bovine milk. The Journal of nutritional biochemistry, 6(7), 362-366.

(2) Cansız D, Ünal İ, Üstündağ ÜV, Alturfan AA, Altinoz MA, Elmacı İ, Emekli-Alturfan E. Caprylic acid ameliorates rotenone induced inflammation and oxidative stress in the gut-brain axis in Zebrafish. Mol Biol Rep. 2021 Jun;48(6):5259-5273. doi: 10.1007/s11033-021-06532-5.