High Concentrate Vitamin C
Vitamin C, a water-soluble and charged molecule, can be delivered into the epidermis layer by topical application. The effectiveness depends on the formulation. Penetration only occurs at a pH below 4 when Vitamin C is present as L-ascorbic acid. L-ascorbic acid (LAA) is the chemically active form of Vitamin C. Although far less stable than its derivatives, pure ascorbic acid is far more active because it does not first have to undergo hydrolysis to turn it into the active form.
In general, Vitamin C is known for its antioxidative properties. It neutralizes and removes radicals to prevent oxidative damage to skin. In addition, it reduces melanin synthesis due to its ability to interfere with the action of tyrosinase. The property of Vitamin C to reduce melanin synthesis is used to treat skin hyperpigmentation in conditions such as melasma or age spots. Besides, L-Ascorbic acid acts as a co-factor for enzymes that stabilize the collagen molecule structure and promotes collagen synthesis. Vitamin C also accelerates differentiation of keratinocytes, ensuring the function of the skin barrier and preventing skin water loss. All this leads to an improvement of elasticity, skin firmness, winkle depth, skin roughness, skin tone and radiance.
1] Shindo et al., Journal of Investigative Dermatology 102, 1994.  Humberg et al., Experimental Dermatology; 12, 2003.  Nuygens et al., Journal of Investigative Dermatology 116, 2001.  Smith, International Journal of Cosmetic Science 21, 1999.  Savini et al., Journal of Investigative Dermatology 118, 2002.  Pinnell et al., Dermatologic Surgery; 27: 137-42, 2001.