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Retinoinds, such as retinoic acid (a.k.a. tretinoin, Retin-A), are a group of biochemical agents proven to improve fine lines, wrinkles and other signs of skin aging. Unfortunately, they can be irritating in sensitive individuals and if used improperly may do more harm than good (see the article on retinoids). One alternative is to use less irritating precursors, the substances that are themselves inactive but can be converted to active (directly-acting) retinoids in the body.
The most common such precursors in skin care are the forms of vitamin A, retinol and retinyl palmitate. Unfortunately, while less irritating, retinol and retinyl palmitate are usually less effective than retinoic acid and other directly acting retinoids. The primary reason is that they need to undergo at least two metabolic conversion steps before becoming retinoic acid. Such conversion tends to be slow and its rate varies from person to person. As a result, anti-aging effects of retinol and retinyl palmitate tend to be more modest and less reliable than those of retinoic acid and analogous retinoids (see our article retinol / retinyl palmitate). Another long-known form of vitamin A, retinaldehyde (a.k.a. retinal), is just one metabolic step away from retinoic acid and is more effective than either retinol or retinyl palmitate (see our retinaldehyde article for details). Yet, while less irritating than retinoic acid, retinaldehyde still causes skin irritation in a significant number of people. Furthermore, both retinol and retinaldehyde have stability issues, especially when exposed to sunlight.
Enter retinyl retinoate, a new retinoid precursor and vitamin A derivative that reportedly combines high effectiveness, favorable side effect profile (e.g. low capacity to produce skin irritation) and good stability (compared to other vitamin A derivatives and retinoids).
Retinyl retinoate is a molecule that is produced by chemically joining the molecules of retinoic acid and retinol. In the body, just one metabolic step is required to split it back into retinoic acid and retinol, at which point retinoic acid is immediately active whereas retinol can be converted to additional retinoic acid later on. As a result, biological activity of retinyl retinoate in the skin is reportedly higher than that of retinol (and possibly even retinaldehyde) and may be approaching that of retinoic acid itself.
On the other hand, since retinyl retinoate is inactive until converted and the conversion is gradual, it likely produces a milder and more gradual rise in the skin levels of retinoic acid (compared to direct application of retinoic acid). Such dynamics leads to less irritation because it helps avoid excessive spikes in skin levels of retinoic acid.
The Achilles heel of many retinoid precursors (particularly retinol and retinaldehyde) is stability. Even if a retinol or retinaldehyde product survives until the actual use (due to a good formulation and proper storage), it often gets inactivated by exposure to sunlight soon after application, which results in reduced effectiveness. Notably, retinyl retinoate is reported to be more resistant to inactivation by sunlight than retinol and most other forms of vitamin A. If true, this would make it an especially practicable choice for skin care formulations.
If all of the above sounds encouraging to you – it is. However, keep in mind that retinyl retinoate is a newcomer and has not been studied as much as other retinoids and their precursors. I'll try to summarize some of the research below.
In a 2010 laboratory study in hairless mice, Korean researchers from R&D Center of Skin Science and Cosmetics, Enprani, Incheon, found that retinyl retinoate increased the production of hyaluronic acid (an imporatnt water-holding skin matrix polymer) by boosting HAS2, the enzyme that synthesizes hyaluronic acid. Furhermore, the application of retinyl retinoate was associated with less transepidermal water loss than retinol, retinoic acid and retinaldehyde. In other words, retinyl retinoate appeared to produce less skin damage and irritation than other retinoids and retinoid precursors.
In a 2010 Korean split-face study, doctor H. Kim and co-workers from Yonsei University in Seoul treated forty six women (30+ y.o; divided in two equal groups) with either topical 0.06% retinyl retinoate vs placebo, or 0.06% retinyl retinoate vs 0.075% retinol, with each agent applied to one half of the face. The former group was treated for 12 weeks and the latter for 8 weeks. The results were analyzed based on photodamage scores, photographs and visiometer data. The researchers found that retinyl retinoate fared not only better than placebo but also better than retinol based on objective measurements as well as subjective reports of the study subjects. It produced the greatest improvement in wrinkles, skin roughness and other parameters. No severe side effects were observed in retinyl retinoate treated subjects.
The same team of Korean researchers compared topical retinyl retinoate in a standard vehicle to retinyl retinoate encased in microspheres made of polylactic acid (PLA). The researchers reported that retinyl retinoate formulation with PLA-microspheres performed modestly better and the benefits were achieved at a somewhat faster rate.
The above results are encouraging and are consistent with our current understanding on the biochemistry of retinoids and their role in skin biology. However, it is a concern that most research into the skin effect of retinyl retinoate appears to come from a single source – a team (or perhaps two overlapping teams) of South Korean researchers. Having these results confirmed by multiple fully independent teams would go far to boost the case for retinyl retinoate in skin care.
Retinyl retinoate is a promising new retinoid precursors and vitamin A derivative. It may approach retinoic acid (a.k.a. tretinoin, Retin-A) in effectiveness yet produce far less irritation. It may also be more stable than comparable retinoid precusror and vitamin A derivatives, such as retinol and retinaldehyde. Thus retinyl retinoate may possess the best features of retinoids and retinoid precursors all in itself. Unfortunately, all the research on retinyl retinoate appears to come from the same source, which makes it much harder to rely on the findings, however encouraging they may seem. Before retinyl retinoate can be recognized as an established and possibly superior skin care agent, its benefits need to be proven in studies conducted by other independent teams of researchers.
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