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Chapter 26: Hyaluronic Acid

INTRODUCTION

Activities:

Humectant, antiaging

Important Chemical Components:

Hyaluronic acid (HA) is formed by repeating units of the disaccharides D-glucuronic acid and D-N-acetylglucosamine, which are linked to each other by alternating β-1,4 and β-1,3 glycosidic bonds. HA is composed of carbon, hydrogen, nitrogen, and oxygen (molecular formula: C14H21NO11). See Figure 26-1.

Origin Classification:

HA is isolated from bacterial or yeast cultures, so it is considered natural but laboratory made. It is not considered organic.

Personal Care Category:

Humectant, moisturizer

Recommended for the following Baumann Skin Types:

DRNT, DRNW, DRPT, DRPW, DSNT, DSNW, DSPT, and DSPW, but only if used in a humid environment or with an occlusive ingredient. ORNW, ORPW, OSNW, and OSPW in any environment.

FIGURE 26-1

Hyaluronic acid is composed of repeating dimers of glucuronic acid and N-acetyl glucosamine assembled into long chains.

An illustration shows the structure of hyaluronic acid. The illustration shows the structure of hyaluronic acid. The structure contains repeating units of the disaccharides D-glucuronic acid and D-N-acetylglucosamine linked by glyosidic bonds. The structure of disaccharides D-glucuronic acid contains a 6-carbon ring in which the first carbon is bonded to hydrogen and an oxygen that is bonded to the third carbon of D-N-acetylglucosamine. The second and third carbon is boded to a hydrogen and a hydroxyl group. The fourth carbon is bonded to a hydrogen and an oxygen. The fifth carbon is bonded to a hydrogen and carboxyl group. The first and fifth carbon are bonded to an oxygen. The structure of D-N-acetylglucosamine contains a 6-carbon ring in which the first carbon is bonded to hydrogen and an oxygen. The second carbon is bonded to an amine that is wedged bonded to a carbon that is double bonded to an oxygen and wedged bonded to a methyl group. Third carbon is bonded to a hydrogen and oxygen of the first carbon of D-glucuronic acid. Fourth carbon is bonded to a hydrogen and a hydroxy group. Fifth carbon is bonded to a hydrogen and a hydroxy methyl group.
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SOURCE

Hyaluronic acid (HA), or hyaluronan, is the most abundant glycosaminoglycan (GAG) found in the human dermis (Table 26-1). GAGs are polysaccharide chains made up of repeating disaccharide units linked to a core protein. Together the GAGs (HA, dermatan sulfate, heparin, heparin sulfate, keratin sulfate, chondroitin-4, and chondroitin-6-sulfate) and attached core proteins form proteoglycans. The only nonsulfated GAG and the only one not synthesized on a core protein, HA is produced by an enzyme complex of the plasma membrane.1 In addition, HA is a hygroscopic sugar that can bind over 1,000 times its weight in water. It is responsible for giving skin its plumpness and volume. HA is made by fibroblasts and broken down by the enzyme hyaluronidase.

TABLE 26-1Pros and Cons of Hyaluronic Acid
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TABLE 26-1 Pros and Cons of Hyaluronic Acid

PROS

CONS

Strong humectant

Penetration into skin depends on size

Nonimmunogenic

Does not penetrate into the dermis

Forms reservoirs in the epidermis

High consumer recognition

May effect cytokines

Dehydrates skin in a dry environment

Enhances drug delivery

Various biological/medical applications

The HA used in skin care products and injectables was originally harvested from rooster combs but now most HA in skin care products is derived from a bacterial origin and produced in the laboratory setting. The molecular weight of the HA varies according to its source and chain length. The HA isolation process can be adjusted to determine its corresponding molecular weight, altering its physiochemical properties.

Uncrosslinked chains of HA in the skin are broken down by hyaluronidase and free radicals in approximately 24 to 36 hours. Chemical modifications, such as crosslinking HA chains with 1,4-butanediol diglycidyl ether (BDDE), can increase the amount of time that HA resides in the skin. Dermal fillers such as Restylane are crosslinked with BDDE so that the HA lasts in the skin for six or more months; ...

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