Capryloyl salicylic acid also referred to as octanoyl salicylic acid, is a lipophilic derivative of salicylic acid. ester of salicylic acid. It is obtained from salicylic acid by extraction from the bark of the willow tree.

The name defines the structure of the molecule:

• "Capryloyl" refers to the portion of caprylic acid, also known as octanoic acid, of the molecule. Caprylic acid is a fatty acid with an eight-carbon chain. In the context of caprylic salicylic acid, caprylic acid has been modified to form an acyl group (a functional group derived from an acid by removal of a hydroxyl group), which is attached to salicylic acid.
• "Salicylic Acid" is a type of phenolic acid and a beta hydroxy acid. It has the formula C₇H₆O₃. This compound is often used in skin care products due to its ability to penetrate the skin and its exfoliating properties.

Description of raw materials used in production:

• Caprylic Acid - Caprylic acid is a fatty acid found in various vegetable oils, such as palm oil and coconut oil. It can be obtained through extraction or chemical synthesis.
• Salicylic Acid - Salicylic acid is a carboxylic acid that can be extracted from willow bark or synthesized from phenol. It is a common ingredient used for its exfoliating and antimicrobial properties.

The synthesis process takes place in several stages:

• Step 1: Preparation of raw materials: caprylic acid and salicylic acid.
• Step 2: Esterification. Caprylic acid and salicylic acid undergo an esterification reaction involving the carboxyl group of caprylic acid and the hydroxyl group of salicylic acid. The result of this reaction is Capryloyl salicylic acid and a water molecule.
• Step 3: Purification. Capryloyl salicylic acid is purified to remove any residue of caprylic acid and unreacted salicylic acid through a series of washing and filtration steps.
• Step 4: Drying. Purified capryloyl salicylic acid is then dried to remove any residual solvent.

It is typically a colourless or white substance in liquid or cream form.

What it is used for and where

Medical
It is used in medicine mainly for the treatment of acne and is compared to benzoyl peroxide. Both produce similar healing results (1). Salicylic acid is a beta hydroxy acid (BHA) that can infiltrate skin pores and remove excess oil and dead skin cells that cause acne.

Cosmetics

It is inserted in cosmetic products, in sun creams and more.

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

It is used to perform superficial facial peels to reduce hyperpigmentation of the face and thinner wrinkles (2).  It helps in the removal of dead skin cells from the surface of the skin, promoting the regeneration of new skin cells and giving the skin a refreshed and rejuvenated appearance.

It can stimulate collagen production, which helps limit the appearance of fine lines and wrinkles. It also stimulates skin cell turnover, which helps improve skin texture and tone.

The caprylic part of the molecule is a chain of fatty acids that increases the molecule's lipophilicity. This helps the molecule reach deeper into the skin, improving its effectiveness.

Safety

As far as human health is concerned, it is considered quite safe (3).

• Molecular Formula: C₁₅H₂₀O₄
• Molecular Weight: 264.321 g/mol
• CAS:  70424-62-3
• EC Number: 
• UNII:
• Synonyms:
• 2-hydroxy-5-octanoylbenzoic acid
• beta-lipohydroxyacid
• 2-hydroxy-5-octanoylbenzoic acid
• Capryloyl salicylic acid
• 5-Octanoylsalicylic acid
• 2-hydroxy-5-(1-oxooctyl)Benzoic acid
• Benzoic acid, 2-hydroxy-5-(1-oxooctyl)-
• 5-octanoyl salicylic acid
• 5-n-octanoylsalicylic acid

References_______________________________________________________________________

(1) Baumann LS, Oresajo C, Yatskayer M, Dahl A, Figueras K. Comparison of clindamycin 1% and benzoyl peroxide 5% gel to a novel composition containing salicylic acid, capryloyl salicylic acid, HEPES, glycolic acid, citric acid, and dioic acid in the treatment of acne vulgaris. J Drugs Dermatol. 2013 Mar;12(3):266-9.

(2) Oresajo C, Yatskayer M, Hansenne I. Clinical tolerance and efficacy of capryloyl salicylic acid peel compared to a glycolic acid peel in subjects with fine lines/wrinkles and hyperpigmented skin.  J Cosmet Dermatol. 2008 Dec;7(4):259-62. doi: 10.1111/j.1473-2165.2008.00403.x.

(3) Cosmetic Ingredient Review Expert Panel. Safety assessment of Salicylic Acid, Butyloctyl Salicylate, Calcium Salicylate, C12-15 Alkyl Salicylate, Capryloyl Salicylic Acid, Hexyldodecyl Salicylate, Isocetyl Salicylate, Isodecyl Salicylate, Magnesium Salicylate, MEA-Salicylate, Ethylhexyl Salicylate, Potassium Salicylate, Methyl Salicylate, Myristyl Salicylate, Sodium Salicylate, TEA-Salicylate, and Tridecyl Salicylate.  Int J Toxicol. 2003;22 Suppl 3:1-108. Review.