Acide ascorbique (Vitamine C, E300)

Ascorbic acid (Vitamin C) is the pure, L-isomer form of vitamin C, a water-soluble compound naturally found in citrus fruits and many vegetables. It is the most bioactive and potent form of vitamin C used in cosmetics, renowned for its ability to inhibit melanin synthesis by blocking tyrosinase activity, stimulate collagen production, and neutralize free radicals — making it a gold-standard brightening and anti-aging active. Formulators value its efficacy but must contend with its notorious instability; it oxidizes rapidly at higher pH levels, in the presence of light, air, or metal ions, requiring careful formulation at pH below 3.5 and use of protective packaging to maintain potency.