Vitamin C: An Effective Skin-Care Active

Vitamin C (Vit. C) is one of the naturally occurring antioxidants in nature. Most plants and animals are able to synthesize Vit C from glucose. Humans are one of the few mammals that can’t produce vitamin C because they lack the enzyme L-gluconolactone oxidase, which converts glucose to ascorbic acid.  hence, they must acquire it from natural sources such as citrus fruits, green leafy vegetables, strawberries, papaya, and broccoli. The absorption of Vit. C in the gut is limited by an active transport mechanism and hence a finite amount of the drug is absorbed despite high oral dosage. The bioavailability of Vit. C in the skin is inadequate when it is administered orally. The use of topical ascorbic acid is therefore favored in the practice of dermatology.

Vitamin C is normally found at high levels in the dermis and epidermis. A study of vitamin C in young, aged, and photo-damaged human skin demonstrated that vitamin C levels were 31 percent lower in the epidermis of photo-damaged skin and 39 percent lower in aged skin. In the dermis, vitamin C levels were 37 percent lower in photo-damaged skin and 30 percent lower in aged skin. Environmental pollutants, such as ozone, can also decrease vitamin C levels in the skin and lead to free-radical damage. Additionally, smoking can lead to increased wrinkling and decreased collagen synthesis, which corresponds to a decline in plasma vitamin C levels.

Vitamin C, or ascorbic acid, has a long history of topical use and is one of the most researched active ingredients used in skincare. Vitamin C is the major water-soluble antioxidant found in the body. As an antioxidant, it destroys free radicals and plays a major role in hydroxylation reactions essential for the formation of collagen

Exposure to UV light reduces the availability of Vit. C in the skin. The exposure of skin to UV light generates reactive oxygen species (ROS) these radicals damage the cells and causes inflammation and skin aging. Clinical studies have shown that the topical use of Vit. C increases collagen production in young as well as aged human skin.

Antioxidants are necessary for neutralizing the ROS formed due to UV exposure. It is important to note that Vit. C is equally effective against both UVB (290-320 nm) and UVA (320-400 nm). UVA penetrates 30-40-times deeper into the dermis as against UVB, which mostly affects the epidermis. UVA changes and destroys collagen, elastin, proteoglycans, and other dermal cellular structures. This causes skin aging and possibly melanoma formation. UVB causes sunburn, epidermal mutations, and skin cancer. Sunscreens block only 55% of the free radicals. To optimize UV protection, it is important to use sunscreens combined with a topical antioxidant. Vit. C does not absorb UV light but exerts a UV-protective effect by neutralizing free radicals, while this effect is not seen with sunscreens. Under laboratory conditions, it has been shown that application of 10% topical Vit. C showed a statistical reduction of UVB-induced erythema by 52% and sunburn cell formation by 40-60%.

Vit. C interacts with copper ions at the tyrosinase-active site and inhibits the action of the enzyme tyrosinase, thereby decreasing the melanin formation. Vit. C also acts on the perifollicular pigment. However, Vit. C is an unstable compound. It is therefore often combined with other depigmenting agents such as soy and licorice for a better depigmenting effect.

Vit. C has a potential anti-inflammatory activity and can be used in conditions like acne vulgaris and rosacea. It can promote wound healing and prevent post-inflammatory hyperpigmentation.

The stability of Vit. C is controlled by maintaining a pH of less than 3.5. At this pH, the ionic charge on the molecule is removed and it is transported well across the stratum corneum

The use of vitamin C (3 to10 percent) in topical applications for at least 12 weeks has been shown to decrease wrinkling, reduce protein fiber damage, decrease apparent roughness of skin and increase production of collagen. Topical vitamin C has also been shown to reverse some of the age-related changes in the epidermis.

Claimed skin benefits for vitamin C and its derivatives:

• Acts as an antioxidant
• It has been shown to reduce the oxidation of squalene in sebum, which contributes to acne
• Reduces fine lines and wrinkles and may thicken the epidermis
• Reduces UV-induced redness and inflammation
• Lightens skin
• Improves acne
• Improves gingivitis

Reference:

Indian Dermatology

Oregon State University