What are the differences between hyaluronic acid and polyglutamic acid?

• Where does thehyaluronic acid come from?

  This biopolymer was first discovered in thevitreous humour of the bovine eye in 1934 by Karl MEYER and John PALMER. It was subsequently extracted from the cartilage of the bovine snout as well as from the comb of the rooster. Naturally present in the human body, it is also found around the joints, in the muscles, in the eye... However, the skin and more specifically the dermis remains the main reservoir of this molecule in the human body. Today, the hyaluronic acid present in cosmetic care is generally obtained by biotechnological synthesis from bacteria.

• Where does thepolyglutamic acid (PGA) come from?

  This compound was first isolated from the body of a marine jellyfish. It enables the jellyfish to store water in its delicate tissue, thereby preventing rapid dehydration caused by its presence in the salty ocean water. Today, PGA is extracted from a traditional Japanese food, the nattô, which is made from fermented soybeans. It can also be biosynthesised from glutamic acid using the Gram-positive bacterium Bacillus subtilis. Therefore, unlike hyaluronic acid, PGA is not naturally present in the human body.

Hyaluronic acid is a non-branched linear chain composed of repetitive disaccharide units of D-glucuronic acid and an aminoglycan, D-N-acetylglucosamine. Polyglutamic acid is a polymer derived from the amino acid L-glutamic. Its raw chemical formula is written as (C5H7NO3)n.

In summary, hyaluronic acid is composed of a polysaccharide chain, while polyglutamic acid is derived from the polymerisation of amino acids.

These two acids are recognised for their moisturising properties in skin and hair care. However, some nuances need to be considered regarding their mode of operation and their penetration into the skin:

• As a natural component of the dermis, hyaluronic acid plays a structural role. It thus acts as a humectant agent capable of retaining water within cells. Its mode of action is directly related to its molecular structure. Indeed, this polymer can bind to hundreds of sulphated proteoglycans to form supramolecular structures. These are then able to establish bonds with water molecules and ions, helping to maintain skin hydration.

  Thus,hyaluronic acid boasts a retention capacity of 1,000 times its weight in water. Moreover, this molecule exists in two molecular weights. High molecular weight hyaluronic acid remains on the surface of the epidermis and creates a protective film that prevents water from evaporating. Low molecular weight hyaluronic acid penetrates deeper into the epidermis, right down to the base of the corneal structure, to stimulate the production of hyaluronic acid naturally produced by the body.

• Thepolyglutamic acid has a larger molecular size than hyaluronic acid. It does not penetrate deeply but rather stays on the surface. Its hydrating action is linked to its ability to form a protective film on the skin's surface that limits water evaporation. This is referred to as a microgel ; this structure swells and traps water, thus promoting its retention.Polyglutamic acid is capable of retaining up to 5,000 times its weight in water.

Thehyaluronic acid is a compound that has been widely used in skincare for several years now, while polyglutamic acid is a recent active ingredient on the market. However, combining these two molecules provides the skin with a hydration boost.

On one hand, hyaluronic acid works on the internal cells of the dermis for long-lasting hydration. It particularly contributes to the oxygenation, toning, and nourishment of the skin. On the other hand, the polyglutamic acid forms a protective film on the surface of the stratum corneum, which prevents water evaporation.

hydrating serum with hyaluronic acid, followed by the plumping serum with polyglutamic acid and red algae extract.

• DINI G.& al. Hyaluronic acid in intrinsic skin ageing.International Journal of Dermatology(1994).

• GOLDMAN D. M. & co. Polyglutamic acid: a new peptide for skincare. Cosmetics Toiletries Magazine (2007).