What are the different forms of vitamin C?

The vitamin C in its pure form, namely L-ascorbic acid (INCI name: Ascorbic Acid), appears as yellowish crystals or powder. This type of vitamin C is the best-known of all and delivers excellent results, particularly on the signs of photoageing and skin radiance. However, ascorbic acid has an acidic pH, around 3.5, a parameter to consider when formulating a pure vitamin C treatment to avoid oxidation issues. Moreover, this acidic pH can be irritating to the skin, whose physiological pH is around 5.5–6. For this reason, in practice, ascorbic acid is infrequently included in cosmetic formulations, and derivatives of vitamin C are often used. They provide similar benefits.

Vitamin C derivatives are generally combinations of ascorbate (vitamin C in a non-acidic form) with alkalising minerals (calcium, magnesium, sodium…).

Sodium ascorbyl phosphate (INCI name: “Sodium Ascorbyl Phosphate”).

The sodium ascorbyl phosphate is a water-soluble derivative of vitamin C designed to bypass the natural instability of ascorbic acid. Thanks to its phosphorylated structure, it is more resistant to oxidation, light and heat, and is considered a more dependable active in aqueous formulations. Once applied to the skin, it can be converted into active ascorbic acid by the action of specific cutaneous enzymes, notably phosphatases, thus ensuring a progressive and controlled release of vitamin C. This also improves tolerability: unlike pure vitamin C, this derivative is less irritating, making it suitable for sensitive skin.

Magnesium ascorbyl phosphate (INCI name: “Magnesium Ascorbyl Phosphate”).

Magnesium ascorbyl phosphate is another water-soluble derivative of vitamin C that is highly stable. Like sodium ascorbyl phosphate, it gradually transforms into ascorbic acid active once applied to the skin, thanks to the action of skin enzymes, thus ensuring a controlled and sustained release of vitamin C. Magnesium ascorbyl phosphate is also suitable for sensitive skin and can, like ascorbic acid, stimulate collagen synthesis, improve skin tone uniformity and attenuate the signs of ageing.

Ascorbyl tetraisopalmitate (INCI name: “Ascorbyl Tetra Isopalmitate”).

The ascorbyl tetraisopalmitate is an oil-soluble derivative of vitamin C, meaning that, unlike ascorbic acid and the forms described below, it is soluble in oil. It thus exhibits excellent affinity for the epidermis and penetrates relatively easily into the stratum corneum, the outermost layer of the skin which is predominantly composed of lipids. Ascorbyl tetraisopalmitate is often found in oils or oil-based serums.

Ascorbyl palmitate (INCI name: "Ascorbyl Palmitate").

The ascorbyl palmitate is a lipid-soluble derivative of vitamin C, obtained by combining ascorbic acid with palmitic acid. This lipid solubility allows it to blend more effectively into oil-based formulations and to penetrate more easily into the epidermal lipid barrier. Like other vitamin C derivatives, it is converted into active ascorbic acid once absorbed and contributes to protecting the skin from oxidative stress.

Ascorbyl glucoside (INCI name: "Ascorbyl Glucoside").

Ascorbyl glucoside is a water-soluble derivative of vitamin C in which ascorbic acid is bound to a sugar (glucose), significantly enhancing its oxidative stability. Once applied to the skin, enzymes in the epidermis hydrolyse this compound to steadily release the active ascorbic acid, thereby ensuring a prolonged action.

3-O ethyl ascorbate (INCI name: "3-O Ethyl Ascorbate").

3-O-ethyl ascorbate is a lipid-soluble and exceptionally stable derivative of vitamin C, designed to resist oxidation and degradation in cosmetic formulations. It stands out for its excellent tolerability and its ability to penetrate the skin rapidly, enabling swift action.

At Typology, we primarily use derivatives in our vitamin C treatments, in particular "Sodium Ascorbyl Phosphate", "Ascorbyl Tetraisopalmitate", "3-O-Ethyl Ascorbic Acid" and "Ascorbyl Glucoside".

• TELANG P. S. Vitamin C in dermatology. Indian Dermatology Online Journal (2013).

• LEONARDI G. R. & al. Cosmetics formulations containing vitamin C and the instability challenge. Research Journal of Topical and Cosmetic Sciences (2022).

• GOLD M. H. & al. Vitamin C: Its role in cosmeceuticals. Dermatological Reviews (2024).

• ROBLES VELASCO M. V. & al. New discoveries of the action of L-ascorbic acid (vitamin C) – Enhanced efficacy in formulations. Brazilian Journal of Pharmaceutical Sciences (2025).