Polyglutamic acid, a good active ingredient for hydrated skin.

Thepolyglutamic acid or PGA is a peptide derived from the polymerization of glutamic acid. It is the main component of nattō, a Japanese dish made with fermented soybeans. Traditionally, PGA was used in medicine to accelerate the healing processes of wounds and burns of varying severity. While it is primarily consumed today for its nutritional benefits, recent studies have explored its cosmetic benefits. These studies have highlighted its excellent moisturizing and soothing properties. Polyglutamic acid is also effective in reducing the appearance of wrinkles.

This biopolymer combats skin dehydration at various levels:

• Polyglutamic acid is a film-forming agent.

  In other words, it forms a film microscopic on the surface of the epidermal tissue. This molecular arrangement is referred to as a microgel. This microgel swells upon contact with water and traps H2O molecules. Thus, not only does polyglutamic acid limit transepidermal water loss, but it also promotes its retention through a moisturizing process. A 2014 study revealed that PGA had a more hydrating effect than hyaluronic acid. Indeed, it is capable of retaining up to 5,000 times its weight in water. In comparison, hyaluronic acid retains up to 1,000 times its weight in water.

• Polyglutamic acid stimulates the production of substances that make up the Natural Moisturizing Factor (NMF).
  The NMF is a set of hygroscopic molecules (amino acids, urea...) that form duringtheepidermal differentiation process and retain water in the skin's superficial layer. Polyglutamic acid boosts the production of some of these molecules, including pyrrolidone carboxylic acid (PCA), lactic acid, and urocanic acid.

• Polyglutamic acid limits the activity of the hyaluronidase.

  Hyaluronidase is the enzyme responsible for the breakdown of hyaluronic acid, a molecule predominantly produced by the fibroblasts of the dermis (deep layer of the skin) that gives the skin its plump and bouncy appearance. Hyaluronic acid acts like a molecular sponge, capturing water. Over the years, its content decreases: by the age of 50, the stock of hyaluronic acid would have thus decreased by half. This drastic drop leads to an atrophy of the fat pockets located deep in the dermis, resulting in the appearance of wrinkles and fine lines on the skin's surface. By inhibiting the activity of the hyaluronidase enzyme, polyglutamic acid therefore prevents skin dehydration and the appearance of aging signs.

Note : While PGA aids in maximizing the hydration of the epidermis, it cannot, however, act in depth due to its excessively high molecular weight. Its action is limited to the superficial layers of the skin. Low molecular weight hyaluronic acid is more recommended for deep skin hydration.