Acide ascorbique

Ascorbic acid (Vitamin C) is the purest and most bioavailable form of vitamin C used in cosmetics, a water-soluble lactone naturally found in citrus fruits and many vegetables. It is highly prized by formulators for its potent ability to inhibit melanin synthesis by blocking tyrosinase activity, stimulate collagen production, and neutralize free radicals, making it a cornerstone active in brightening and anti-aging serums. Its primary formulation challenge lies in its notorious instability — it oxidizes rapidly upon exposure to light, air, and alkaline pH — which is why it requires careful encapsulation, low-pH formulations (typically below 3.5), and opaque or airless packaging to maintain efficacy.