Vitamin C (Vit. C) is one of the naturally occurring antioxidants in nature. Most plants and animals are able to synthesise Vit. C from glucose. Humans and certain other vertebrates lack the enzyme L-glucono-gamma lactone oxidase required for ongoing synthesis of Vit. C; hence, they must acquire it from natural sources such as citrus fruits, green leafy vegetables, strawberries, papaya and broccoli. The word “Ascorbus” means no Scurvy. Traditionally, Vit. C-rich foods like lemons were carried by sailors on long journeys to avoid Scurvy, a disease of bleeding gums.
L-ascorbic acid (LAA) is the chemically active form of Vit. C. In nature, Vit. C is found in equal parts as LAA and D-ascorbic acid. 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. Furthermore, 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 the most plentiful antioxidant in human skin, forms a part of the complex group of enzymatic and non-enzymatic antioxidants that co-exist to protect the skin from reactive oxygen species (ROS) or, "free radicals". When the skin is exposed to UV light, ROS such as the superoxide ion, peroxide and singlet oxygen are generated. Vit. C protects the skin from oxidative stress by sequentially donating electrons to neutralize the free radicals. Exposure to UV light reduces the availability of Vitamin C in the skin.
This exposure of skin to UV light generates ROS.[1] These radicals have a potential to start chain or cascade reactions that damage the cells. The harmful effects of ROS occur as direct chemical alterations of the cellular DNA, the cell membrane and the cellular proteins, including collagen. Although Vitamin C alone can provide photoprotection, it works best in conjunction with Vitamin E (Vit. E), which potentiates the action of Vit. C four-fold. Hydrophilic Vit. C helps regenerate Vit. E, a liphophilic antioxidant.
Vit. C is essential for collagen biosynthesis. It has been proposed that Vit. C influences quantitative collagen synthesis in addition to stimulating qualitative changes in the collagen molecule.[2] Vit. C serves as a co-factor for the enzymes prolysyl and lysyl hydroxylase, the enzymes that are responsible for stabilizing and cross-linking the collagen molecules.[2] Another mechanism by which Vit. C influences the collagen synthesis is by stimulation of lipid peroxidation, and the product of this process, malondialdehyde, in turn stimulates collagen gene expression.[2]
When choosing a depigmenting agent, it is important to differentiate between substances that are toxic to the melanocyte and substances that interrupt the key steps of melanogenesis. Vit. C falls into the latter category of depigmenting agents. Vit. C interacts with copper ions at the tyrosinase-active site and inhibits action of the enzyme tyrosinase, thereby decreasing the melanin formation.
Topical Vit. C is largely safe to use on a daily basis for long durations. It can safely be used in conjunction with other common topical anti-ageing agents such as sunscreens, tretinoin, other antioxidants and alfa hydroxy acids such as glycolic acid. Minor adverse reactions include a yellowish discoloration of the skin, hypopigmented hair and staining of clothes, which occur due to oxidative changes of Vit. C. Once applied, Vit. C cannot be fully washed or wiped off the skin. Rarely, stinging, erythema and dryness are observed after use of topical Vit. C. These can easily be treated using a moisturiser. Care must be taken while applying Vit. C around the eyes.
Taken From:
Telang PS. Vitamin C in dermatology. Indian Dermatol Online J. 2013 Apr;4(2):143-6. doi: 10.4103/2229-5178.110593. PMID: 23741676; PMCID: PMC3673383.
(1) Farris PK. Cosmetical Vitamins: Vitamin C. In: Draelos ZD, Dover JS, Alam M, editors. Cosmeceuticals. Procedures in Cosmetic Dermatology. 2nd ed. New York: Saunders Elsevier; 2009. pp. 51–6.
(2) Traikovich SS. Use of Topical Ascorbic acid and its effects on Photo damaged skin topography. Arch Otorhinol Head Neck Surg. 1999;125:1091–8. doi: 10.1001/archotol.125.10.1091.
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