Vitamin C Derivatives

Vitamin C derivatives are chemically modified forms of ascorbic acid designed to be more stable, less irritating or more oil-compatible than pure vitamin C, while still delivering its brightening and antioxidant benefits. They are widely used as gentler alternatives in serums, creams and moisturisers.

Pure L-ascorbic acid is effective but notoriously unstable, oxidising quickly and requiring a low, sometimes irritating pH to remain active. Derivatives address this by attaching the ascorbic acid to another molecule, such as a phosphate, sugar or fatty chain. Once absorbed, the skin is thought to convert many of them back into active vitamin C through enzymatic activity, although conversion efficiency varies between derivatives and is not always well quantified.

• Sodium ascorbyl phosphate and magnesium ascorbyl phosphate: water-soluble, stable at near-neutral pH, often studied for oil control and brightening.
• Tetrahexyldecyl ascorbate (THD ascorbate): oil-soluble, valued for stability and penetration into the skin's lipid layers.
• Ascorbyl glucoside: sugar-linked and generally well tolerated.

Because they are milder, derivatives are frequently chosen for sensitive skin or for formulas combined with other actives. The trade-off is that a derivative is not identical to ascorbic acid, and evidence for each form differs; some are better supported than others. As with all vitamin C, benefits accumulate gradually with consistent use, and pairing with daily sun protection is recommended for visible improvement in tone and radiance.