Acide ascorbique (E300)

Ascorbic acid (Vitamin C) is the purest and most bioavailable form of Vitamin C used in cosmetics, a water-soluble compound naturally found in citrus fruits and many vegetables. It is highly prized for its potent antioxidant activity, its ability to inhibit melanin synthesis by blocking tyrosinase, and its role in stimulating collagen biosynthesis, making it a cornerstone active in brightening and anti-aging formulations. Formulators must account for its notorious instability — it oxidizes rapidly when exposed to light, air, and alkaline pH — which requires careful formulation at low pH (below 3.5), use of opaque or airless packaging, and often combination with stabilizing co-antioxidants such as ferulic acid or tocopherol.