PEG-8 caprylic/capric glycerides is a chemical compound, alkyl glyceride, a mixture derived from PEG (PEG stands for Polyethylene glycol) from caprylic and capryc acids oil mono- and diglycerides. The number appearing after the abbreviation PEG refers to mol of ethylene oxide and the higher this number is, the less it can penetrate the skin.

The name describes the structure of the molecule:

• PEG-8 indicates that the molecule has eight units of ethylene oxide. "PEG" stands for polyethylene glycol.
• Caprylic/Capric refer to fatty acids derived mainly from coconut oil. Caprylic acid has an 8-carbon chain, while capric acid has a 10-carbon chain.
• Glycerides indicates that the molecule is an ester derived from glycerin and the mentioned fatty acids (caprylic and capric).

Raw Materials Used in Production.

• Caprylic/Capric glycerides are triglycerides derived primarily from the fatty acids of coconut oil or palm kernel oil.
• Ethylene oxide is a chemical compound used to produce polyethoxylated compounds, like PEGs.

Step-by-step Summary of Industrial Production Process.

• Extraction of glycerides. Caprylic/capric glycerides are extracted from oils such as coconut or palm kernel.
• Ethoxylation reaction. The glycerides react with ethylene oxide to form the polyethoxylated compound.
• Purification. The product is purified to remove impurities and byproducts.

Form and Color.

PEG-8 Caprylic/Capric Glycerides typically appears as a clear to slightly cloudy viscous liquid.

What it is used for and where

Cosmetics

Skin conditioning agent - Emollient. Emollients have the characteristic of enhancing the skin barrier through a source of exogenous lipids that adhere to the skin, improving barrier properties by filling gaps in intercorneocyte clusters to improve hydration while protecting against inflammation. In practice, they have the ability to create a barrier that prevents transepidermal water loss.  Emollients are described as degreasing or refreshing additives that improve the lipid content of the upper layers of the skin by preventing degreasing and drying of the skin. The problem with emollients is that many have a strong lipophilic character and are identified as occlusive ingredients; they are oily and fatty materials that remain on the skin surface and reduce transepidermal water loss. In cosmetics, emollients and moisturisers are often considered synonymous with humectants and occlusives.

Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable. Emulsifiers have the property to reduce the oil/water or water/oil interfacial tension, improve emulsion stability and also directly influence the stability, sensory properties and surface tension of sunscreens by modulating their filmometric performance.

It is used as a co-emulsifier for creams and lotions in oil/water mixtures and as a makeup remover in skin cleansing products.

Medical

Pharmaceutical excipient and skin penetration enhancer.

PEG-8 caprylic/capric glycerides can be obtained by partial alcoholization of medium-chain triglycerides using PEG, by esterification of glycerol and PEG with caprylic acid and capric acid, or as a mixture of glycerol esters and ethylene oxide condensates with caprylic acid and capric acid (1).

PEG-8 caprylic/capric glycerides consist of 30% mono-, di-, and triglycerides of C8 and C10 fatty acids, 50% mono- and diesters of PEG, and 20% of PEG-8.18. They contain ≤10 ppm 1,4-dioxane (2),

Safety

The term 'eth' refers to the ethoxylation process (reaction with ethylene oxide) after which residues of ethylene oxide and 1,4-dioxane, chemical compounds considered carcinogenic, may remain in the final product. It depends on the degree of purity resulting from the completed reaction.

Concentrations of caprylic/capric glycerides at 0.5-3.0% PEG-8 were not found to be irritating to rabbit eyes, while a concentration of 5.0% was mildly irritating (3).

The most relevant studies on this chemical compound have been selected with a summary of their contents:

PEG-8 caprylic/capric glycerides studies

References______________________________________________________________________

(1) Council of Experts. Caprylocaproyl polyoxyglycerides. http://www.pharmacopeia.cn/v29240/usp29nf24s0_m12363.html.  U.S.Pharmacopeia. Date Accessed 5-27-2014.

(2) Gattefossé. Technical data sheet: Labrasol.  http://www.gattefosse.com/media/document/tds_labrasol.PDF. Date Accessed 5-14-2014. 

(3) Liu Z, Zhang X, Li J, Liu R, Shu L, Jin J. Effects of Labrasol on the corneal drug delivery of baicalin. Drug Deliv. 2009 Oct;16(7):399-404. doi: 10.1080/10717540903126165.  

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And a premise on PEG.

Since the PEG (1) family is numerous and is found in many cosmetic, cleaning and medicinal products and others, we need a cognitive premise on the subject that is rather complex from the point of view of safety because these products not only come into contact with the skin but, as in the case of medicine, they are also ingested.

PEG or polyethylene glycols polymerise the condensed ethylene oxide and water and are called polyethylene glycols, but in reality, they are complex chemical components, polymers bound together. For example,  plastic is polyethylene and has a hard consistency, while  polyethylene aggregated to the glycol forms a liquid.

The number that appears after the initials PEG represents the molecular weight and the higher this number is, the less it penetrates  the skin. 

Here below are some studies in Medicine that refer to the use of PEG Polyethylene glycol in various fields.

Intestine

Polyethylene glycol with or without electrolytes is effective for the treatment of functional constipation, both in adults and in paediatric patients, with great safety and tolerability. These preparations are the most effective osmotic laxatives (more than lactulose) and are the first-line treatment for functional constipation in the short- and long-term. They are as effective as enemas in faecalomas, avoid the need for hospitalisation and are well tolerated by patients (especially when given without electrolytes) (2).

In the preparation  for colonoscopy,  polyethylene glycol tablets confirmed efficacy, acceptability, tolerance and safety similar to those of sodium phosphate (3).

For peripheral nerve repair (4).

Eyes

Dry eye syndrome is a disorder that affects 5-34% of the world's adult population with reduced quality of life. Artificial or lubricating tears are the most used therapy for treating this condition due to their low side effects profile, which attempt to modify the properties of the tear film. Polyethylene glycol has demonstrated clinical efficacy in the treatment of this condition (5).

Brain

Polyethylene glycol facilitates the neuroprotective effects of magnesium in head injuries (6).

Tumors

For transarterial chemoembolization, Polyethylene glycol is effective and safe for the treatment of liver cancer, as indicated by good tolerability, quality of life and high tumour response (7). 

Cosmetics

Many types of PEG are hydrophilic and are used as creams, topical dermatological preparations and in cosmetic products such as surfactants, emulsifiers, detergents, humectants and skin conditioners.

Safety varies from type to type given the structural complexity (8).

References___________________________________________________________________

(1) Fruijtier-Pölloth C. Safety assessment on polyethylene glycols (PEGs) and their derivatives as used in cosmetic products. Toxicology. 2005 Oct 15;214(1-2):1-38. doi: 10.1016/j.tox.2005.06.001.

(2) Mínguez M, López Higueras A, Júdez J. Use of polyethylene glycol in functional constipation and fecal impaction. Rev Esp Enferm Dig. 2016 Dec;108(12):790-806. doi: 10.17235/reed.2016.4571/2016.

Santos-Jasso KA, Arredondo-García JL, Maza-Vallejos J, Lezama-Del Valle P. Effectiveness of senna vs polyethylene glycol as laxative therapy in children with constipation related to anorectal malformation. J Pediatr Surg. 2017 Jan;52(1):84-88. doi: 10.1016/j.jpedsurg.2016.10.021.

(3) Chaussade S, Schmöcker C, Toulemonde P, Muñoz-Navas M, O'Mahony V, Henri F. Phosphate tablets or polyethylene glycol for preparation to colonoscopy? A multicentre non-inferiority randomized controlled trial. Surg Endosc. 2017 May;31(5):2166-2173. doi: 10.1007/s00464-016-5214-1.
Tsunoda T, Sogo T, Iwasawa K, Umetsu S, Oikawa-Kawamoto M, Inui A, Fujisawa T. Feasibility and safety of bowel cleansing using low-volume polyethylene glycol with ascorbic acid before pediatric colonoscopy: A pilot study. Dig Endosc. 2017 Mar;29(2):160-167. doi: 10.1111/den.12756.

(4) Hoffman AN, Bamba R, Pollins AC, Thayer WP. Analysis of polyethylene glycol (PEG) fusion in cultured neuroblastoma cells via flow cytometry: Techniques & optimization. J Clin Neurosci. 2017 Feb;36:125-128. doi: 10.1016/j.jocn.2016.10.032.

(5) Pérez-Balbuena AL, Ochoa-Tabares JC, Belalcazar-Rey S, Urzúa-Salinas C, Saucedo-Rodríguez LR, Velasco-Ramos R, Suárez-Sánchez RG, Rodríguez-Carrizalez AD, Oregón-Miranda AA. Efficacy of a fixed combination of 0.09 % xanthan gum/0.1 % chondroitin sulfate preservative free vs polyethylene glycol/propylene glycol in subjects with dry eye disease: a multicenter randomized controlled trial. BMC Ophthalmol. 2016 Sep 20;16(1):164. doi: 10.1186/s12886-016-0343-9.

Labetoulle M, Messmer EM, Pisella PJ, Ogundele A, Baudouin C. Safety and efficacy of a hydroxypropyl guar/polyethylene glycol/propylene glycol-based lubricant eye-drop in patients with dry eye. Br J Ophthalmol. 2017 Apr;101(4):487-492. doi: 10.1136/bjophthalmol-2016-308608.

(6) Busingye DS, Turner RJ, Vink R. Combined Magnesium/Polyethylene Glycol Facilitates the Neuroprotective Effects of Magnesium in Traumatic Brain Injury at a Reduced Magnesium Dose. CNS Neurosci Ther. 2016 Oct;22(10):854-9. doi: 10.1111/cns.12591.

(7) Aliberti C, Carandina R, Sarti D, Mulazzani L, Catalano V, Felicioli A, Coschiera P, Fiorentini G. Hepatic Arterial Infusion of Polyethylene Glycol Drug-eluting Beads for Primary and Metastatic Liver Cancer Therapy. Anticancer Res. 2016 Jul;36(7):3515-21.

(8) Jang HJ, Shin CY, Kim KB. Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use. Toxicol Res. 2015 Jun;31(2):105-36. doi: 10.5487/TR.2015.31.2.105.