INTRODUCTION
Ultraviolet (UV) radiation generates reactive oxygen species (ROS) in the skin that can oxidize nucleic acids, lipids, and proteins. This oxidative stress in the skin is associated with photoaging and skin cancer.1 UV radiation also has been shown to induce matrix metalloproteinases (MMPs), which degrade dermal collagen and elastin. One of the ways skin naturally protects itself against UV damage is with antioxidants that neutralize the ROS that cause damage.1 Based on this scientific
evidence, the cosmetic skin care industry has popularized anti-aging creams and serums, many with added vitamins and other antioxidants. We provide a synopsis of many of these ingredients
as well as an evaluation of the literature discussing their use in the treatment of photoaged skin.
Common Cosmeceutical Active Ingredients
Retinoids and Vitamin A
There is extensive literature on the use of topical retinoids, which are derivatives of vitamin A, a naturally occurring antioxidant in the skin. Tretinoin, or all-trans retinoic acid, is the biologically active form of vitamin A and one of the few therapeutic agents proven to repair photodamage.2 It has been shown to improve fine facial wrinkles, mottled hyperpigmentation, and skin roughness. 3 However, tretinoin is often associated with skin irritation and is available only in prescription formulations. Retinoids available in OTC formulations, which include retinol, retinaldehyde, and retinyl palmitate, are less potent than tretinoin.
There is extensive literature on the use of topical retinoids, which are derivatives of vitamin A, a naturally occurring antioxidant in the skin. Tretinoin, or all-trans retinoic acid, is the biologically active form of vitamin A and one of the few therapeutic agents proven to repair photodamage.2 It has been shown to improve fine facial wrinkles, mottled hyperpigmentation, and skin roughness. 3 However, tretinoin is often associated with skin irritation and is available only in prescription formulations. Retinoids available in OTC formulations, which include retinol, retinaldehyde, and retinyl palmitate, are less potent than tretinoin.
Retinol
Retinol is oxidized into retinaldehyde and then into retinoic acid, the biologically active form of vitamin A. A 2000 study found that treatment with 1% retinol reduces MMP expression and stimulates collagen synthesis in both sun-protected and photoaged skin.4 Also, randomized controlled trials found significant improvement in fine wrinkles after 12 and 24 weeks of treatment, respectively.5-7 Retinol is one of the best-studied active in OTC products and consistently has been shown to improve photoaged skin.
Retinol is oxidized into retinaldehyde and then into retinoic acid, the biologically active form of vitamin A. A 2000 study found that treatment with 1% retinol reduces MMP expression and stimulates collagen synthesis in both sun-protected and photoaged skin.4 Also, randomized controlled trials found significant improvement in fine wrinkles after 12 and 24 weeks of treatment, respectively.5-7 Retinol is one of the best-studied active in OTC products and consistently has been shown to improve photoaged skin.
Retinaldehyde
Retinal or retinaldehyde is the aldehyde form of vitamin A. Retinaldehyde is often an intermediate during the conversion of retinol to retinoic acid.8 Studies have shown that retinaldehyde can produce significant improvement in the appearance of both fine and deep wrinkles.9,10
Retinal or retinaldehyde is the aldehyde form of vitamin A. Retinaldehyde is often an intermediate during the conversion of retinol to retinoic acid.8 Studies have shown that retinaldehyde can produce significant improvement in the appearance of both fine and deep wrinkles.9,10
Retinyl Palmitate
Retinyl palmitate is the ester of retinol and palmitic acid. Although retinyl palmitate has not yet been proven to be an effective anti-aging agent, it has been shown to inhibit the formation of thymine dimers in the presence of UVB rays.11 It also is one of the active ingredients in an OTC product that was shown to produce significant fibrillin-1 deposition in a clinical study.12
Retinyl palmitate is the ester of retinol and palmitic acid. Although retinyl palmitate has not yet been proven to be an effective anti-aging agent, it has been shown to inhibit the formation of thymine dimers in the presence of UVB rays.11 It also is one of the active ingredients in an OTC product that was shown to produce significant fibrillin-1 deposition in a clinical study.12
α-Hydroxy Acids
α-Hydroxy acids (AHAs) are a class of compounds that consist of a carboxylic acid substituted with a hydroxyl group on the adjacent carbon. They are commonly seen on many OTC product
labels as glycolic acid, malic acid, lactic acid, citric acid, α-hydroxyethanoic acid, α-hydroxyoctanoic acid, hydroxycaprylic
acid, α-hydroxycaprylic acid, and hydroxyl fruit acids.
