The secret of young skin seems to be unrevelled: Hyaluronic acid is the miracle agent that promises a youthful look forever. Nevertheless, the compound is not new: it occurs naturally and is responsible for many important functions in the human body.
With acids we generally associate strongly corrosive liquids that should not come in contact with human skin. Naturally, one would not expect that hyaluronic acid is a suitable substance for our skin. However, the strength of acids varies greatly, and hyaluronic acid is only a relatively week, organic carboxylic acid that causes no harm for human skin being also slightly acidic itself. Hyaluronic acid is build up from a long chain of sugar molecules, to be more specific it is a oligomer of β(1→4’) glycosidal connected disaccharides. Those disaccharides consist of two units being related to glucose, D-glucoronic acid and N-acetyl-D-glucosamine being β(1’→3) glycisodal connected.
A hyaluronic acid chain contains typically between 250 and 50000 disaccharide units. These chains are held together between each other by hydrogen bonds, mostly between the carboxylic acid and N-acetyl groups. This way, a tight netweork is formed that can hold up to six liters of water per gram hyaluronic acid. Hyaluronic can therefore be viewed as a natural superabsorber that are nowadays applied in modern diapers to keep babys dry.
Our body uses this property to an advantage by producing itself hyaluronic acid in areas where a great amount of water needs to be stored with little effort. A good example is the vitreous body of the human eye which consists almost exclusively of water and of 2% hyaluronic acid.
For our joints hyaluronic acid also plays an important role: Together with water being contained in our joints as well hyaluronic acid acts as a superb grease and shock absorber at the same time. If large shearing forces are being applied the viscosity of the hyluronic acid/water conglomerate is reduced, which allows smooth movement of the joints. Upon great pressure however, the hyaluronic acid chains aggreagte encompassing water molecules inside the conglomerate, thus creating a water cushion to counter a sudden stop of movement. Also for the spinal disk hyaluronic acid serves as a shock absorber as well as keeping the vertebrae at a distane to prevent abrasion.
There are many dfferent applications of hyaluronic acids in medicine: It is injected into ones joints to cure arthrosis, it is used in nasal sprays and in eye drops to prevent dryness of the mucosa or the eyes. It is also used in the therapy of incontinence.
> > >Part 2:_The beauty industry discovers hyaluronic acid
Photo credits
Human eye: GNU_Free Documentation License on Wikimedia Commons
Articles on the topic (in part only at the German mirror):
Q10_-_forever young?! | Wenn_die_Haare_nicht_mehr_sprießen | Haarige_Reaktionen_-_die_Chemie_auf_unseren_Köpfen
