Sodium Cocoyl Glutamate

What is Sodium Cocoyl Glutamate?

It is an amino acid-based surfactant that belongs to the acylglutamate group which is known to be one of the mildest and moisturizing groups of surfactants. 

What are its Benefits?

• Reduce the absorption of other surfactants like Sodium Lauryl Ether Sulfates
• Soften hard water by removing minerals
• Carboxyl groups in the surfactant support the low pH of the skin
• Degraded by enzymes (Odland bodies) in the skin into Glutamic Acid and Fatty Acids
• Optimized proprietary blend with Sodium Cocoyl Glycinate and Cocamidopropyl Hydroxysultaine selectively solubilizes Squalene without solubilizing Intercellular Lipids

One of the common problems of surfactants is their potential to disrupt the organization of the intercellular cement lipids in the stratum corneum (i.e. ceramides, cholesterol, and fatty acids). Even the supposedly mildest Decyl Glucoside (Almost non-existent irritation in Zein Protein Dissolution, RBC test, Acute Eye Irritation Assay, HET-CAM)^[1] were shown to solubilize Cholesterol and Fatty acids.^[2] Acylglutamates are considered non-delipidants, as cholesterol and other intercellular cement lipids are not soluble in them. To test this, 5% of Sodium Cocoyl Glutamate was compared with 5% Cocamidopropyl Betaine, Sodium Lauryl Sulfate, Sodium Laureth Sulfate, and 5% of the proprietary blend. Sodium Cocoyl Glutamate, and the proprietary blend resulted in the least amount of solubilized intercellular lipids.^[3] This result is consistent with previous studies done to measure the amount of lipids extracted by surfactants. The results showed that acylglutamates have sufficient detergency to extract squalane but not barrier lipids such as cholesterol. In the same study, keratinocyte cytotoxicity was assessed and acylglutamates were superior in mildness with NR50 of 306 compared to 36 for acylmethyl taurate, 16.8 for sodium cocoyl isethionate, 9.9 for soap and 4.1 for SLS.^[4] In addition, the SC orderliness was also assessed by in-vitro ESR spin probe method showing that acylglutamates have an order parameter (S) of 0.73 compared to SLS 0.47, soap 0.65, water 0.89 (S=1 representing control).^[5] Another study showed that acylglutamates strip off NMF at negligible amounts compared to soap or other anionic surfactants.^[6] In congruence with the past studies, mobility and orientation of the intercellular lipids were tested and correlated with TEWL which gave further credence to the mildness of Sodium Cocoyl Glutamate.^[7]

How does it compare to other surfactants?

Although SCG is proven to be milder than most surfactants, entry to the skin is still possible. Hence, it is beneficial to use surfactants that degrade upon entry into the stratum corneum. Even though they are great non-delipidants, we believe that they would still have little to some disrupting effect on the stratum corneum lipids as they are still considered anionic surfactants. Thankfully, specialized organelles called Odland bodies that results from keratinization are extruded in the extracellular space for various functions including lipid processing. These organelles contain enzymes that are able to process Sodium Cocoyl Glutamate into Glutamic acid and various chain fatty acids. Glutamic acid resulting from the cleavage would serve as a base into the formation of various Natural Moisturizing Factors such as PCA.

Compared to Sodium lauroyl glutamate, Sodium Cocoyl Glutamate is less irritating to the skin. Lauroyl is a C12 straight-chain similar to Cocoyl. The difference is that, although the major component of cocoyl is C12 (40%), the remaining components are actually longer alkyl chains. It is known that longer alkyl groups, particularly those that are branched or contain aromatic groups penetrate less compared to shorter alkyl groups.^[8]

Glutamate based surfactants are also considered to be more bio-compatible as the major component of the stratum corneum is keratin, which is composed of alternating acidic and basic residues forming alpha-helical rods. This supports the observation that, although glutamates penetrate further into the skin compared to glycinates, their penetration results in less disruption of the keratin structures.^[9]

In theory, this makes sense, but as to whether enough Sodium Cocoyl Glutamate is processed by Odland bodies in the stratum corneum is yet to be elucidated. Although its irritation potential and selective solubilization, and the ability to disrupt the organized structure of intercellular layers have been tested, further studies involving in-vivo visualization of SC after SCG cleansing should be performed. One drawback of acylglutamate is the cost as it is deemed impractical due to cost.

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