Vitamin C has the effect of preventing and treating ascorbic acid, hence it is also known as ascorbic acid and is a water-soluble vitamin. Natural vitamin C is mostly found in fresh fruits (apples, oranges, kiwifruit, etc.) and vegetables (tomatoes, cucumbers, and cabbage, etc.). Due to the lack of the key enzyme in the final step of vitamin C biosynthesis in the human body, namely L-glucuronic acid 1,4-lactone oxidase (GLO), vitamin C must be taken from food.
The molecular formula of vitamin C is C6H8O6, which is a strong reducing agent. The two enol hydroxyl groups on the 2 and 3 carbon atoms in the molecule are easily dissociated and release H+, thereby oxidizing to form dehydrogenated vitamin C. Vitamin C and dehydrogenated vitamin C form a reversible redox system, exerting various antioxidant and other functions, and playing an important role in the human body. When applied to the field of cosmetics, vitamin C has functions such as whitening and promoting collagen formation.
The efficacy of vitamin C
There are two main mechanisms by which vitamin C has a whitening effect on the skin. The first mechanism is that vitamin C can reduce the dark oxygen melanin during the production process of melanin to reducing melanin. The color of melanin is determined by the quinone structure in the melanin molecule, and vitamin C has the property of a reducing agent, which can reduce the quinone structure to a phenolic structure. The second mechanism is that vitamin C can participate in the metabolism of tyrosine in the body, thereby reducing the conversion of tyrosine into melanin.
Free radicals are harmful substances produced by the body’s reactions, which have strong oxidizing properties and can damage tissues and cells, leading to a series of chronic diseases. Vitamin C is a water-soluble free radical scavenger that can eliminate free radicals such as – OH, R -, and O2- in the body, playing an important role in antioxidant activity.
Promote collagen synthesis
There is literature indicating that daily topical application of formulations containing 5% L-ascorbic acid in the skin can increase the mRNA expression levels of type I and type III collagen in the skin, and the mRNA expression levels of the three types of invertases, carboxycollagenase, aminoprocollagenase, and lysine oxidase also increase to a similar extent, indicating that vitamin C can promote the synthesis of collagen in the skin.
In addition to antioxidant effects, vitamin C also has a prooxidant effect in the presence of metal ions, and can cause lipid, protein oxidation, and DNA damage, thereby affecting gene expression. Vitamin C can reduce the peroxide (H2O2) to hydroxyl radical and promote the formation of oxidative damage by reducing Fe3+to Fe2+and Cu2+to Cu+. Therefore, it is not recommended to supplement vitamin C for people with high iron content or those with pathological conditions related to iron overload such as thalassemia or hemochromatosis.