Vitamin C - different forms and different effects in cosmetics

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Vitamin C is one of the best researched and most widely used active ingredients in cosmetics. Its popularity is due to its broad spectrum of action, including antioxidant protection, support for collagen synthesis and its effect on evening out skin tone. At the same time, vitamin C is not a homogeneous component - in cosmetics comes in many chemical forms that differ in stability, solubility, bioavailability and dermal tolerance profile. Understanding these differences is crucial both at the formulation stage and in assessing product safety and efficacy.

The role of vitamin C in skin physiology

Vitamin C (L-ascorbic acid) is a natural antioxidant present in the skin, where it participates in neutralising free radicals formed, among others, under the influence of UV radiation and environmental pollution. It also plays an important role in collagen synthesis by participating in the hydroxylation of proline and lysine - processes necessary for the correct formation of collagen fibres.

In cosmetics, vitamin C:

• supports the antioxidant protection of the skin,
• contributes to improving firmness and elasticity,
• affects the lightening of hyperpigmentation by modulating tyrosinase activity,
• supports the regeneration of skin exposed to oxidative stress.

It is worth emphasising that Vitamin C is not a substitute for sunscreen, but can complement the skin's protection against the effects of UV exposure.

Ascorbic acid - Reference form

L-ascorbic acid is the biologically active form of vitamin C and is the benchmark for other derivatives. It demonstrates high efficacy, but its use in cosmetics presents specific formulation challenges.

Features and limitations vitamin C

• high biological activity,
• low stability in the aquatic environment,
• sensitivity to light, oxygen and elevated temperatures,
• the need for a low pH formulation,
• Potential for irritation, especially in people with sensitive or vascular skin.

For these reasons, ascorbic acid is often used in combination with other antioxidants (e.g. vitamin E, ferulic acid) and in air-restricted packaging.

Stable vitamin C derivatives

To increase stability and improve skin tolerance, different vitamin C derivatives are used in cosmetics. Each is characterised by a different solubility, activity and application profile.

Ascorbyl phosphates (MAP, SAP)

Ascorbyl magnesium phosphate (MAP) and ascorbyl sodium phosphate (SAP) are water-soluble forms with greater stability compared to ascorbic acid. They have a milder effect and are therefore often used in products for sensitive or problematic skin.

SAP is sometimes used in formulations for acne-prone skin due to its additional properties supporting the skin's microbiological balance. MAP is used in brightening and anti-ageing products, where good tolerability is important for long-term use.

Ascorbyl glucoside

Ascorbyl glucoside is a stable, water-soluble vitamin C derivative that is gradually converted to ascorbic acid on the skin surface. It thus provides a milder, staggered effect.

The form:

• is characterised by good stability,
• is well tolerated by sensitive skin,
• is used in daily care products.

Ascorbyl tetraisopalmitate

Ascorbyl tetraisopalmitate is a lipophilic oil-soluble vitamin C derivative. It is distinguished by its high stability and ability to penetrate the lipid layer of the epidermis.

The use of this form includes:

• oil and anhydrous formulations,
• anti-ageing products,
• cosmetics designed for sensitive skin requiring good tolerance.

Selection of the form of vitamin C according to product and skin type

The choice of the appropriate form of vitamin C should be the result of analysis:

• the purpose of the cosmetic,
• skin type and sensitivity,
• Formulation pH,
• the expected performance profile,
• the stability of the product throughout its shelf life (see stability studies).

There is no single „best” form of vitamin C - each has legitimate technological and functional uses. The role of cosmetics laboratory R&D is about consciously selecting the form of vitamin C for a specific formulation, taking into account the safety of the user.

Use of cosmetics with vitamin C

Cosmetics containing vitamin C are most commonly used in morning care. They are recommended to be combined with sun protection to enhance protection against oxidative stress.

The concentration and form of vitamin C should be adjusted individually. For sensitive skin, it is recommended to start with milder derivatives and lower concentrations.

The importance of vitamin C in cosmetic formulations - a laboratory approach

From the perspective of the cosmetics laboratory, vitamin C is an ingredient that requires special attention:

• in terms of formulation stability,
• choice of packaging,
• compatibility with other ingredients,
• safety assessments and skin tolerance.

Proper formulation design allows the potential of vitamin C to be realised in a safe and effective manner, regardless of the form chosen.

Summary

Vitamin C is a valuable ingredient in cosmetics, offering a broad spectrum of action and numerous formulation options. The variety of available forms makes it possible to tailor a product to specific skin needs and user expectations. It is crucial to consciously select the form of vitamin C and reliably assess its stability and safety, in accordance with the principles of modern cosmetology and laboratory practice.