Dihydroxyacetone

Dihydroxyacetone

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Dihydroxyacetone , or DHA, also known as glycerone, is a simple carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 (a triose
Triose
A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses: L-Glyceraldehyde and D-Glyceraldehyde, both aldotrioses because the carbonyl group is at the end of the chain, and dihydroxyacetone, a ketotriose because the carbonyl group is in...

) with formula .

DHA is primarily used as an ingredient in sunless tanning
Sunless tanning
Sunless tanning Sunless tanning Sunless tanning (also known as UV-free tanning, self tanning, spray tanning (when applied topical, or fake tanning) refers to the application of chemicals to the skin to produce an effect similar in appearance to a suntan...

 products. It is often derived from plant sources such as sugar beet
Sugar beet
Sugar beet, a cultivated plant of Beta vulgaris, is a plant whose tuber contains a high concentration of sucrose. It is grown commercially for sugar production. Sugar beets and other B...

s and sugar cane, and by the fermentation of glycerin.

Chemistry


DHA is a hygroscopic white crystalline powder. It has a sweet cooling taste and a characteristic odor. It is the simplest of all ketose
Ketose
A ketose is a sugar containing one ketone group per molecule.With 3 carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the only one having no optical activity. Ketoses can isomerize into an aldose when the carbonyl group is located at the end of the molecule...

s and, having no chiral center, is the only one that has no optical activity. The normal form is a dimer which is slowly soluble in one part water and 15 parts ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

. When freshly prepared, it reverts rapidly to the monomer in solution. The monomer is very soluble in water, ethanol, diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

 and acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

 and toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...

.

DHA may be prepared, along with glyceraldehyde
Glyceraldehyde
Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. It is the simplest of all common aldoses. It is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism...

, by the mild oxidation of glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, for example with hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 and a ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....

 salt as catalyst. It can also be prepared in high yield and selectivity at room temperature from glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

 using a cationic neocuproine-based palladium catalyst with oxygen or air acting as the co-oxidant. Glyceraldehyde is a structural isomer of dihydroxyacetone.

Biology


Its phosphate form, dihydroxyacetone phosphate (DHAP) takes part in glycolysis
Glycolysis
Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...

, and it is an intermediate product of fructose metabolism.

Uses


DHA was first recognized as a skin coloring agent by German scientists in the 1920s. Through its use in the X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 process, it was noted as causing the skin surface to turn brown when spilled.

In the 1950s, Eva Wittgenstein at the University of Cincinnati did further research with dihydroxyacetone. Her studies involved using DHA as an oral drug for assisting children with glycogen storage disease
Glycogen storage disease
Glycogen storage disease is the result of defects in the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types. GSD has two classes of cause: genetic and acquired. Genetic GSD is caused by any inborn error of metabolism involved in these processes...

. The children received large doses of DHA by mouth, and sometimes spat or spilled the substance onto their skin. Healthcare workers noticed that the skin turned brown after a few hours of DHA exposure.

Eva Wittgenstein continued to experiment with DHA, painting liquid solutions of it onto her own skin. She was able to consistently reproduce the pigmentation effect, and noted that DHA did not penetrate beyond the stratum corneum
Stratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells that lack nuclei and organelles. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress...

, or dead skin surface layer. Research then continued on DHA's skin coloring effect in relation to treatment for patients suffering from vitiligo
Vitiligo
Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...

.

This skin browning effect is non-toxic, and similar to the Maillard reaction
Maillard reaction
The Maillard reaction is a form of nonenzymatic browning similar to caramelization. It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat....

. DHA reacts chemically with the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s in the skin, which are part of the protein containing keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

 layer on the skin surface. Various amino acids react differently to DHA, producing different tones of coloration from yellow to brown. The resulting pigments are called melanoidin
Melanoidin
Melanoidins are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine at high temperatures and low water activity. Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning, such as barley malts , bread...

s. These are similar in coloration to melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

, the natural substance in the deeper skin layers which brown or "tan", from exposure to UV rays
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

.

Winemaking


Both acetic acid bacteria A. aceti and G. oxydans use glycerol
Glycerol
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

 as a carbon source to form dihydroxyacetone. DHA is formed by ketogenesis
Ketogenesis
Ketogenesis is the process by which ketone bodies are produced as a result of fatty acid breakdown.-Production:Ketone bodies are produced mainly in the mitochondria of liver cells. Its synthesis occurs in response to low glucose levels in the blood, and after exhaustion of cellular carbohydrate...

 of glycerol. It can affect the sensory quality of the wine with sweet/etherish properties. DHA can also react with proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...

 to produce a "crust-like" aroma. Dihydroxyacetone can affect the anti-microbial activity in wine, as it has the ability to bind SO2.

Sunless tanning


Coppertone introduced the first consumer sunless tanning
Sunless tanning
Sunless tanning Sunless tanning Sunless tanning (also known as UV-free tanning, self tanning, spray tanning (when applied topical, or fake tanning) refers to the application of chemicals to the skin to produce an effect similar in appearance to a suntan...

 lotion into the marketplace in the 1960s. This product was called “Quick Tan” or “QT”. It was sold as an overnight tanning agent, and other companies followed with similar products. Consumers soon tired of this product due to unattractive results such as orange palms, streaking and poor coloration. Because of the QT experience, many people today still associate sunless tanning with fake-looking orange tans.

In the 1970s the United States Food and Drug Administration (FDA) added DHA permanently to their list of approved cosmetic ingredients.

By the 1980s, new sunless tanning formulations appeared on the market and refinements in the DHA manufacturing process created products that produced a more natural looking color and better fading. Consumer concerns surrounding damage associated with UV tanning options spurred further popularity of sunless tanning products as an alternative to UV tanning. Dozens of brands appeared on drugstore shelves, in numerous formulations.

Today, DHA is the main active ingredient in all sunless tanning skincare preparations. It may be used alone or combined with other tanning components such as erythrulose
Erythrulose
D-Erythrulose is a tetrose carbohydrate with the chemical formula C4H8O4. It has one ketone group and so is part of the ketose family...

. DHA is considered the most effective sun-free tanning additive.

Sunless tanning
Sunless tanning
Sunless tanning Sunless tanning Sunless tanning (also known as UV-free tanning, self tanning, spray tanning (when applied topical, or fake tanning) refers to the application of chemicals to the skin to produce an effect similar in appearance to a suntan...

 products contain DHA in concentrations ranging from 1% to 15%. Most drugstore products range from 3% to 5%, with professional products ranging from 5% to 15%. The percentages correspond with the product coloration levels from light to dark. Lighter products are more beginner-friendly, but may require multiple coats to produce the desired color depth. Darker products produce a dark tan in one coat, but are also more prone to streaking, unevenness, or off-color tones. The artificial tan takes 2 to 4 hours to begin appearing on the skin surface, and will continue to darken for 24 to 72 hours, depending on formulation type.

Once the darkening effect has occurred, the tan will not sweat off or wash away with soap or water. It will fade gradually over 3 to 10 days, in conjunction with the skin's normal exfoliation process. Exfoliation, prolonged water submersion, or heavy sweating can lighten the tan, as these all contribute to rapid dead skin cell exfoliation (the dead skin cells are the tinted portion of the sunless tan.)

Current sunless tanners are formulated into sprays, lotions, gels, mousses, and cosmetic wipes. Professional applied products include spray tanning booths, airbrush
Airbrush
An airbrush is a small, air-operated tool that sprays various media including ink and dye, but most often paint by a process of nebulization. Spray guns developed from the airbrush and are still considered a type of airbrush.-History:...

 tan applications, and hand applied lotions, gels, mousses and wipes.

DHA does not damage the skin, and is considered a safe skin coloring agent and nutritional supplement. Contact dermatitis
Contact dermatitis
Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....

 is rarely reported, however a recent study showed that DHA causes severe contact dermatitis
Contact dermatitis
Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....

 in Mexican hairless dogs. Most cases of sensitivity are due to other ingredients in the skin product preparation, such as preservatives, plant extracts, dyes or fragrances.

DHA has been approved for cosmetic use by the FDA, the Canadian Health Ministry, and most of the EU member nations.

DHA-based sunless tanning has been recommended by the Skin Cancer Foundation, American Academy of Dermatology Association, Canadian Dermatology Association and the American Medical Association
American Medical Association
The American Medical Association , founded in 1847 and incorporated in 1897, is the largest association of medical doctors and medical students in the United States.-Scope and operations:...

.

DHA safety considerations


For the 24 hours after self-tanner (containing high DHA levels, ~5%) is applied, the skin is especially susceptible to free-radical damage from sunlight, according to a 2007 study led by Katinka Jung of the Gematria Test Lab in Berlin. Forty minutes after the researchers treated skin samples with high levels of DHA they found that more than 180 percent additional free radicals formed during sun exposure compared with untreated skin. Another self-tanner ingredient, erythulose, produced a similar response at high levels. For a day after self-tanner application, excessive sun exposure should be avoided and sunscreen should be worn outdoors, they say; an antioxidant cream could also minimize free radical production. Although some self-tanners contain sunscreen, its effect will not last long after application, and a fake tan itself will not protect the skin from UV exposure.

The study by Jung et al. further confirms earlier results demonstrating that dihydroxyacetone in combination with dimethylisosorbide enhances the process of (sun-based) tanning. This earlier study also found that dihydroxyacetone also has an effect on the amino acids and nucleic acids which is bad for the skin.
The free radicals are due to the generation of AGE (Advanced Glycation Products) such as amadori products (a type of AGE) as a result of the reaction of DHA with the skin. AGEs are behind the damage to the skin that occurs with high blood sugar in diabetes where similar glycation occurs.

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