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Différentes sous-classes de céramides.

The Different Types of Ceramides

Ceramides quickly became associated with hydration and thus found their way into the development of skin care products. "EOS ceramides," "NS ceramides," "NP ceramides..." They can be found under various INCI names in ingredient lists. But what are these different subclasses of ceramides all about?

What You Should Know About the Different Ceramide Classes

Ceramides are the product of a reaction between a sphingoid base and a saturated or monounsaturated fatty acid.

The wide variety of ceramides differs depending on the type of sphingoid base and the type of associated fatty acid.

In the epidermis, 16 subclasses of ceramides have been identified.

Ceramides – What Are They?

Ceramides, along with cholesterol (25%) and free fatty acids (25%), are essential and protective lipid components of the skin. A healthy epidermis is composed of approximately 50% ceramides, thus their presence is so important. Ceramides act as "intercorneocyte cement": they ensure good cohesion between the cells of the stratum corneum and thus keep the epidermis intact. They slow down water loss, the entry of harmful external substances and provide suppleness.

With age or due to external influences (UV rays, temperature fluctuations, pollution, etc.), when their content decreases, the skin barrier weakens and the skin becomes drier, resulting in sallow, rough skin that is more susceptible to external stressors and dehydration. This is where ceramide-based skincare products come in to compensate for this deficit and thus rebuild the skin barrier.

Ceramides – A Large Family of Lipids

Ceramides are polar lipids that belong to the sphingolipid family, are structurally heterogeneous and complex and therefore appear in INCI lists under different names. They are formed by the combination of a long-chain sphingoid base with a fatty acid via an amide bond.

Ceramides are of synthetic or plant origin and are classified into different groups depending on the number of carbon atoms of the fatty acid (between 16 and 36 carbons), the degree of unsaturation (saturated or monounsaturated) and the chain length of the sphingoid.

The nomenclature used to name ceramides is based on a letter code that refers to the chemical changes of the different types of ceramides. The first letter informs about the type of modification of the fatty acid: N stands for a non-hydroxylated fatty acid, A for a fatty acid hydroxylated in α-position, O for a fatty acid hydroxylated in ω-position and EO if the ω-hydroxylated acid is esterified. The second letter defines the type of sphingoid base: S stands for sphingosine, P for phytosphingosine, H for 6-hydroxy-sphingosine, dS for dihydroxysphingosine, and T for dihydroxy-sphinganine.

Note: The original nomenclature of ceramides was based on a series of numbers from 1 to 8, corresponding to the six chromatographically separated ceramide fractions determined in human skin. The higher the number, the greater the polarity.

This thus results in a total number of 18 different types of skin ceramides. These include: Ceramide AdS (ceramide 11), Ceramide AH (ceramide 7), Ceramide AP (ceramide 6), Ceramide AS (ceramide 5), Ceramide EAS or 1-O-EAS, Ceramide ENS or 1-O-ENS, Ceramide EOdS, Ceramide EOH (ceramide 4), Ceramide EOP (ceramide 9), Ceramide EOS (ceramide 1), Ceramide OS, Ceramide OH, Ceramide OP, Ceramide NdS or NG (ceramide 10), Ceramide NH (ceramide 8), Ceramide NP (ceramide 3), Ceramide NS (ceramide 2) and Ceramide NT.

Things to know about these subclasses of ceramides.

  • Ceramides AdS, AH, AP and AS have a very similar structure to ceramides NdS, NH, NP and NS, but they differ in the hydroxylation of the fatty acid in the α-position.

  • In esterified ceramides, esterification can occur either at the fatty acid moiety in the ω-position (EO), usually with linoleic acid, or at the primary hydroxyl in the 1-position of the sphingoid base (1-O-E), usually with a saturated acyl chain.

  • Esterification provides ceramides with better stability against oxidative influences.

  • Ceramides whose "fatty acid" part is hydroxidized in the ω (O) position are the least abundant in the human stratum corneum.

  • Ceramides of the dihydroxysphingosine (dS) type differ from those of the sphingosine (S) type by the absence of the trans double bond in the main group, which then makes it more permeable to water and various substances.

  • The class of ceramides whose fatty acid moiety is esterified in the ω-position is known as acylceramides.

  • Ceramides with a non-hydroxylated fatty acid (N) is the group of ceramides most abundant in the stratum corneum compared to all ceramide subclasses, especially the NP and NS ceramides.

Our lip mask contains NS ceramides, which help repair the skin barrier, as well as moisturizing hyaluronic acid (INCI name: Sodium Hyaluronate) and nourishing mango butter (INCI name: Mangifera Indica Seed Butter).

Sources

  • GHIDONI R. & al. Ceramide composition of the psoriatic scale. Biochimica et Biophysica Acta (1993).

  • DOBNER B. & al. Characterisation of a new ceramide EOS species/ synthesis and investigation of the thermotropic phase behaviour and influence on the bilayer architecture of stratum corneum lipid model membranes. Soft Matter (2011).

  • HELDRETH B. & al. Safety assessment of ceramides as used in cosmetics. Cosmetic Ingredient Review (2015).

  • NEUBERT R. H. H. & al. State of the art in stratum corneum research/ the biophysical properties of ceramides. Chemistry and Physics of Lipids (2018).

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