56 SKIN CARE
Special isomer of the vitamin E family
Corinne Déchelette – Kensing ABSTRACT
Although vitamin E was discovered 100 years ago, we have to admit that today it remains a little-known vitamin. Indeed, when the term vitamin E is mentioned, few people, including scientists, realize that it is a generic term covering a family of eight molecules that exhibit an antioxidant activity and that tocopherol is the scientific denomination. Moreover, the knowledge of the stereochemistry of the vitamin E is necessary to understand why RRR-α-tocopherol is a special vitamin E isomer, as the human body is selectively enriched in human tissues because α-tocopherol is the only one that is efficiently taken up by the human body. This selectivity for α-tocopherol is largely conferred by two hepatic activities, an α-tocopherol transport protein (α-TTP) and a catabolizing cytochrome P450 system that preferentially degrades the other dietary forms of vitamin E. This explains why there is an α -tocopherol/ γ -tocopherol molar ratio in the human dermis and epidermis of 10:1. The skin, as the body’s outermost organ, is persistently and directly exposed to a peroxidative environment (exposome) characterized by factors such as UV radiation and pollution. This exposure results in cumulative oxidative stress and oxy-ageing, particularly at the cell membrane level. Vitamin E is the physiological lipophilic antioxidant that inhibits peroxidation of the plasma membrane lipids. However, UV exposure depletes over 90% of this endogenous vitamin E in the stratum corneum when it is excreted onto the skin surface via the sebaceous duct, highlighting the need for topical application of vitamin E and especially, RRR-α-tocopherol that is the more physiologic stereoisomer only be obtained pure by extraction from plants as chemical synthesis results in a racemate of the vitamin E 8 isomers
Although vitamin E was discovered 100 years ago (Figure 1), we have to admit that today it remains a little-known vitamin or it is only known as the ‘vitamin of cosmetics preservation’, which is very restrictive. Vitamin E was discovered in 1922 by Evans and Bishop as a vital dietary biomolecule for mammalian reproduction and was originally named Factor X.1 According to the obvious function in
reproduction, vitamin E got the name tocopherol by Barnet Sure in 1924.2
tokos (τοκος), the Greek word for childbirth, and from pherein (φερειν) for to bear. An ‘ol’ was added to indicate that the molecule had alcohol properties.3
In 1930,
Cummings and Mattell, two researchers specialized on oxidative stress, showed the very great vulnerability of tocopherols to oxidation, which led them to think that the role of this vitamin E was to be oxidized instead of other elements of the human body;4 ‘sacrifices itself’ to protect the body.
vitamin E
Vitamin E, a complex family of vitamers Tocopherol is the scientific denomination of Vitamin E. However, Vitamin E is a collective term that refers to all tocol and tocotrienol derivatives that exhibit the antioxidant activity of α-tocopherol.
PERSONAL CARE May 2025 The name is derived from
However, when the term vitamin E is
mentioned, few people, including scientists, realize that it is a generic term covering a family of eight vitamers (Figure 2): four tocopherol isomers: α, β, γ, δ and four tocotrienol isomers.4 Other vitamins, such as vitamin C correspond to a single molecule, not a family of isomers.
A chiral vitamin that explains the difference between natural and synthetic vitamin E The eight vitamers of Vitamin E family are molecules including three chiral carbons in R (rectus) configuration. However, not all vitamin E forms are processed equally by the body. Regardless of the dietary intake of vitamin,
α-tocopherol is selectively enriched in human tissues. Indeed, out of the four analogs α, β, γ, δ tocopherol, α-tocopherol is the only one that is efficiently taken up by the human body through α-TTP (α-Tocopherol Transfer Protein).4 RRR-α-tocopherol is the most interesting
stereoisomer with a configuration corresponding to the perfect alignment of CH3 methyl groups. Such specificity implies that the body requirement for vitamin E is not of generic antioxidant, but of a specific molecule provided with specific functions. The chemist Paul Karrer was the first who synthetized vitamin E in 1938.5 However, the position of the methyl groups
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