L-4-Hydroxy Proline, (also referred to as Hydroxy Proline or Hydroxyproline), is an amino acid, a building block of protein, made by modifying another amino acid called Proline. It is the primary component of collagen, a fibrous protein found in the dermis of the skin that gives skin its structural support and youthful firmness. Collagen is also the major component of connective tissue, the material that provides structural report for most organs in the body. In the skin, collagen is synthesized by cells called fibroblasts. This process requires vitamin C. Hydroxyproline also plays an important role in wound healing and is a vital component of bones and teeth.
Hydroxy Proline is a major component of the protein collagen. Hydroxy Proline and proline play key roles for collagen stability. Hydroxy Proline is found in few proteins other than collagen. For this reason, Hydroxy Proline content has been used as an indicator to determine collagen and/or gelatin amount. Hydroxy Proline rich glycoproteins are also found in plant cell walls.
Hydroxyproline has the potential to decrease fine lines and wrinkles when used topically and also helps to increase penetration into the skin of other anti-aging skin care ingredients. In addition, hydroxyproline binds water, making it an effective moisturizer and skin conditioner. Another study showed that participants that took hydroxyproline as an oral supplement experienced less skin dryness and better skin texture. Whether hydroxyproline penetrates deeply enough to increase collagen synthesis is still unclear, but, at the very least, it appears to be an efficient moisturizer.