Acide ascorbique (E300, Vitamine C)

Ascorbic acid (Vitamin C) is the purest and most bioavailable form of Vitamin C used in cosmetics, a water-soluble lactone found naturally in citrus fruits and leafy vegetables. It is highly prized for its potent antioxidant activity, 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. However, its notorious instability — it oxidizes rapidly upon exposure to air, light, and heat — presents a significant formulation challenge, requiring low pH environments (below 3.5), anhydrous systems, or encapsulation technologies to maintain efficacy.