Humectant

Hydroxyproline

Amino acid that is an exclusive marker of collagen — over 13% of all amino acids in type I collagen. In cosmetics, it moisturizes, supports skin elasticity, and acts as a signaling peptide for fibroblasts. A biomarker of the effectiveness of collagen products.

amino acidcollagen markerhydrationskin elasticity

✓ Safe

Comedogenic Rating

0/5

Irritation Potential

0/5

What is it?

Hydroxyproline (4-Hyp) — a post-translationally modified form of proline: proline is hydroxylated by the enzyme prolyl hydroxylase (requires vitamin C as a cofactor). Molecular weight ~131 Da. Water-soluble. Unique to animal collagens (human collagen, gelatin, bones). In plants: virtually absent. Function in collagen: stabilizes the triple helix through hydrogen bonds → without hydroxyproline, the collagen helix is unstable → vitamin C deficiency (scurvy) → collagen breakdown. In cosmetics: moisturizer (hygroscopic), signaling molecule, marker of hydrolyzed collagen.

Anti-aging serums and creams with collagen complex, skin elasticity products, moisturizing essences with amino acids, skin recovery products after procedures.

Key Benefits

✦

Signaling action — stimulation of collagen synthesis

Hydroxyproline as a free amino acid or as part of dipeptides (Hyp-Gly, Pro-Hyp) acts as a signaling molecule for fibroblasts: activates TGF-β signaling and increases the expression of collagen-synthesizing genes (COL1A1, COL1A2). Clinically confirmed: oral intake of hydrolyzed collagen (containing Pro-Hyp and Hyp-Gly) increases skin collagen synthesis. When applied topically — the effect is weaker, but present at sufficient concentration.

◈

Hydration and support of elasticity

Hydroxyproline — a hygroscopic amino acid: attracts and retains water from the environment. It is part of the NMF (Natural Moisturizing Factor) of the skin along with other amino acids. When applied topically: moisturizes the stratum corneum, improves elasticity, and reduces the visibility of fine wrinkles. The effect is noticeable at concentrations of 2–5% in aqueous formulations.

✧

Quality marker of collagen products

Since hydroxyproline is almost exclusively found in collagen, the content of free hydroxyproline in hydrolyzed collagen is a direct marker of the degree of hydrolysis and product quality. More hydrolyzed collagen (more free hydroxyproline and short Hyp-peptides) is better absorbed and more effective. When assessing the quality of collagen cosmetic products: hydroxyproline in the INCI composition is a positive signal of the completeness of the amino acid profile.

Suitable for

mature skindehydrated skinanti-aging care

Main Actions

✓ signaling molecule for collagen synthesis✓ hygroscopic hydration✓ support of elasticity

Hydroxyproline vs Proline — different roles

Proline (proline): essential amino acid, structural basis — ~12% of amino acids in collagen. Hydroxyproline: post-translational modification of proline, ~13% of amino acids in collagen, stabilizes the helix. Both are present in collagen hydrolysates. Hydroxyproline is more specific to collagen (almost absent in other proteins) → a better marker of collagen content. In formulations: both have moisturizing effects, but hydroxyproline additionally acts as a signaling molecule.

CategoryHumectants

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