Tocopherol (Vitamin E)

Tocopherol is the ingredient most often misread on a label. It is an antioxidant, not a preservative, and the distinction is not pedantry: it does nothing against bacteria, moulds or yeasts, and it appears nowhere on the list of preservatives that Annex V to Regulation (EC) No 1223/2009 permits in cosmetics sold in the European Union.^[1] A product preserved with tocopherol alone is not preserved.

What it protects is the oil. Unsaturated plant oils react with atmospheric oxygen and turn rancid, deteriorating in smell, colour and texture. Tocopherol interrupts that reaction.

Vitamin E is not one compound but eight: four tocopherols and four tocotrienols, designated alpha, beta, gamma and delta. Alpha-tocopherol has the highest activity in the body and is the form usually meant by the INCI name.

Its working part is a hydroxyl group on a chromanol ring, attached to a long hydrocarbon tail that anchors the molecule in a lipid membrane or an oil phase. When a fat begins to oxidise it generates a peroxyl radical, which would otherwise attack the next fat molecule, and the next. Tocopherol donates the hydrogen from that hydroxyl group and absorbs the radical, becoming a comparatively stable tocopheroxyl radical and breaking the chain.^[2]

The INCI name covers more than one registered substance. Two of them are in the identifier table above: the natural RRR form obtained from vegetable oil, and an all-rac synthetic mixture of eight stereoisomers. They are not nutritionally equivalent, though for antioxidant work inside a jar the difference is small. The plant origin recorded for this entry is the origin of the natural form; the synthetic all-rac shares the INCI name and is not plant-derived, and nothing on a product label distinguishes them.

In 1922 Herbert Evans and Katharine Bishop, at the University of California, reported that rats fed a diet containing every nutrient then known could not carry a pregnancy to term. The foetuses died and were resorbed. Fresh lettuce in the diet prevented it, so an unrecognised factor had to exist.^[3] It was eventually designated vitamin E, and the century of work since has concentrated on its behaviour as a chain-breaking antioxidant.^[4]

Isolation from wheat germ oil followed in the 1930s, and the name tocopherol was built for it from the Greek tokos, childbirth, and pherein, to carry. It records what the deficiency did rather than what the molecule is.

Its arrival in cosmetics owes more to the word vitamin than to the chemistry. Vitamins were a commercial argument in the American beauty industry of the mid-twentieth century, one of a series of scientific vocabularies the trade borrowed to sell a jar,^[5] and tocopherol carried the standing of a nutrient rather than an excipient.

In a formulation tocopherol goes into the oil phase, to extend the life of the oils rather than of the product as a whole. It is consumed in the doing: the act that stops the chain reaction is the donation of a hydrogen atom, and the molecule that donates it is spent.^[6] Tocopherol is sacrificial, and a product that has used up its tocopherol has no further protection from it. How much goes in is a formulation decision rather than a regulated one, and no source consulted here fixes a usual level, so none is given.

Tocopheryl acetate is a common alternative. The acetate is far more stable in storage but is not itself an antioxidant, because the ester has to be cleaved before the molecule can donate anything. It is therefore the better choice for a claim about skin and the worse one for protecting the oils in the jar.

Tocopherol is not listed among the substances prohibited or restricted by the annexes to Regulation (EC) No 1223/2009, and is in ordinary cosmetic use in the European Union.^[7]

The documented problem is allergy, and it belongs mostly to the esters rather than to tocopherol itself. In the spring of 1992 a new cosmetic line in Switzerland produced an epidemic of itching papular and follicular rashes: 263 patients were seen by dermatologists and a further 642 reported directly to the manufacturer. Patch and use testing identified tocopheryl linoleate as the responsible agent.^[8] Isolated cases of allergic contact dermatitis to tocopherol are reported in the dermatological literature, but they are uncommon.