Dihydroxyacetone
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Dihydroxyacetone (; DHA), also known as glycerone, is a simple
saccharide A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' m ...
(a triose) with formula . DHA is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as
sugar beet A sugar beet is a plant whose root contains a high concentration of sucrose and that is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together with ...
s and
sugar cane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...
, and by the fermentation of glycerin.


Chemistry

DHA is a
hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...
white crystalline powder. It has a sweet cooling taste and a characteristic odor. It is the simplest of all
ketose In organic chemistry, a ketose is a monosaccharide containing one ketone () group per molecule. The simplest ketose is dihydroxyacetone (), which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide keto ...
s and has no chiral center. The normal form is a dimer (2,5-bis(hydroxymethyl)-1,4-dioxane-2,5-diol). The dimer slowly dissolves in water, whereupon it converts to the monomer. These solutions are stable at pH's between 4 and 6. In more basic solution, it degrades to brown product. : This skin browning effect is attributed to a Maillard reaction. DHA condenses with the amino acid residues in the protein
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...
, the major component of the skin surface. When injected, no pigmentation occurs, consistent with a role for oxygen in color development. The resulting pigments, which can be removed by abrasion, are called melanoidins. These are similar in coloration to
melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...
, the natural substance in the deeper skin layers which brown or "tan" from exposure to UV rays.


Biochemistry

Its phosphorylated form, dihydroxyacetone phosphate (DHAP), takes part in
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvic acid, pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The Thermodynamic free energy, free energy released in this process is used to form ...
, and it is an intermediate product of fructose metabolism.


Preparation

DHA may be prepared, along with glyceraldehyde, by the mild oxidation of
glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
, for example with
hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
and a
ferrous In chemistry, iron(II) refers to the chemical element, element iron in its +2 oxidation number, oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II ...
salt as
catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
. It can also be prepared in high yield and selectivity at room temperature from
glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
using cationic
palladium Palladium is a chemical element; it has symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1802 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas (formally 2 Pallas), ...
-based
catalysts Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...
with oxygen, air or benzoquinone acting as co-oxidants. Glyceraldehyde is a
structural isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is a compound that contains the same number and type of atoms, but with a different connectivity (i.e. arrangement of bonds) between them. The ...
of dihydroxyacetone. DHA can be derived from plants.


Sunless tanning

DHA is the main active ingredient in many sunless tanning skincare preparations, which may be classified as ''topical sunless tanner'' or ''temporary bronzers''. As opposed to bronzers containing pigment to coat the skin, DHA bronzers cause a coloration of the surface layer of the skin and do not wash off easily. Current sunless tanners are formulated into sprays, lotions, gels, mousses, and cosmetic wipes. Professional applied products include spray tanning booths, airbrush tan applications, and hand applied lotions, gels, mousses and wipes. Lotions often last longer than sprays but may cause blotching and streaking. Mousses and gels tend to dry faster. Mousses generally contain less moisture. Lotion manufacturers also produce a wide variety of sunless tanning preparations that replace DHA with natural bronzing agents such as black walnut shell. DHA may be used alone or combined with other tanning components such as erythrulose. DHA is considered the most effective sun-free tanning additive. Sunless tanning products contain DHA in concentrations ranging from 1% to 20%. Most drugstore products range from 3% to 5%, with professional products ranging from 5% to 20%. 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 7 days as a result of the regular skin exfoliation. Scrubbing the skin, 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). It is recommended to shave, wash, or exfoliate the skin before application in order to produce a more even tan. The skin should not be moisturized before application except very dry areas. Application should be done evenly with a circular motion. Bronzers contain DHA in concentrations from 1 to 15% allowing to adjust the intensity of coloration. DHA formulations have improved in several ways since the introduction in the 1960s.


Safe use and side effects

The
United States Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) has approved DHA for topical application on the skin, but not for contact with eyes, lips, and
mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...
s. DHA may not be used in spray tanning booths due to risk of exposure of these sensitive areas. DHA-containing spray tans have been associated to side effects such as rashes, cough, dizziness, and fainting. Frequent exposure to spray tans may increase the risk of pulmonary disease, asthma, chronic obstructive pulmonary disease (COPD), and cancer. The chemical reaction of DHA in the skin may lead to an unpleasant smell. Fragrances are often added to the formulation to mask the smell, which may lead to allergic reactions or worsen asthma symptoms. Some products contain parabens as chemical preservatives that can cause rosacea and allergic contact dermatitis and act as weak
estrogen Estrogen (also spelled oestrogen in British English; see spelling differences) is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three ...
s. Frequent use of DHA containing products may to be problematic due to a number of side effects. A FDA report concluded that 11 percent of the applied DHA may penetrate into the living cells of the epidermis and dermis. A previous study linked DHA to DNA damage, cell-cycle block, and
apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...
in living cells. Skin coloring induced by frequent use of DHA may interfere with vitamin D production in the skin cells which depends on the exposure to UVB in sunlight. Topical DHA use in levels of more than 5% seem to increase free-radical damage from sunlight for 24 hours after application. Antioxidants may be added to the formulation to produce a more natural tan, and may potentially counteract free radical damage. The use of sunless tanning products may increase the likelihood of sunburn as the artificial coloration of the skin interferes with the natural adaption of the skin to sun exposure. The tanning induced by DHA has been rated with a low sun protection factor (SPF) of 3. It can therefore not replace the application of a regular
sunscreen Sunscreen, also known as sunblock, sun lotion or sun cream, is a photoprotection, photoprotective topical product for the Human skin, skin that helps protect against sunburn and prevent skin cancer. Sunscreens come as lotions, sprays, gels, fo ...
before exposing the skin to intensive sunlight. Erythrulose is a similar agent contained in red raspberries that produces a short-lived reddish tan. The general tanning effect is usually improved when used in combination with DHA. Erythrulose also increases the occurrence of free radicals. DHA may be contained in
moisturizer A moisturizer, or emollient, is a Cosmetics, cosmetic preparation used for protecting, moisturizing, and lubricating the Human skin, skin. These functions are normally performed by Sebaceous gland, sebum produced by healthy skin. The word "emollie ...
s with added fruit extracts sold as "maximizers". Tanning agents labelled as "tingles" contain benzyl nicotinate which presumably aids the production of
melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...
by increasing blood circulation in the skin, thus supplying more oxygen to melanocytes, and often induces a burning or tingling feeling. The effect of products called "optimizers" or "accelerators" containing the protein tyrosine as a precursor in the production of melanin is disputed.


History

DHA was first recognized as a skin coloring agent by German scientists in the 1920s. Through its use in the
X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
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 A glycogen storage disease (GSD, also glycogenosis and dextrinosis) is a metabolic disorder caused by a deficiency of an enzyme or transport protein affecting glycogen synthesis, glycogen breakdown, or glycolysis, glucose breakdown, typically in m ...
. 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. 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 appear to penetrate beyond the
stratum corneum The stratum corneum (Latin language, Latin for 'horny layer') is the outermost layer of the epidermis (skin), epidermis. Consisting of dead tissue, it protects underlying tissue from infection, dehydration, chemicals and mechanical stress. It is ...
, or dead skin surface layer (the FDA eventually concluded this is not entirely true). Research then continued on DHA's skin coloring effect in relation to treatment for patients with
vitiligo Vitiligo (, ) is a chronic autoimmune disorder that causes patches of skin to lose pigment or color. The cause of vitiligo is unknown, but it may be related to immune system changes, genetic factors, stress, or sun exposure, and susceptibili ...
. Coppertone introduced the first consumer sunless tanning 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 suit 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 still associate sunless tanning with fake-looking orange tans. In the 1970s the
United States Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(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 ( sunbathing, indoor tanning) spurred popularity of sunless tanning products as an alternative to UV tanning. Dozens of brands appeared on drugstore shelves, in numerous formulations.


Winemaking

Both
acetic acid bacteria Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which Oxidation, oxidize sugars or ethanol and produce acetic acid during Aerobic fermentation, fermentation. The acetic acid bacteria consist of 10 genus, genera in the family Acet ...
'' Acetobacter aceti'' and '' Gluconobacter oxydans'' use
glycerol Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pha ...
as a carbon source to form dihydroxyacetone. DHA is formed by ketogenesis of glycerol. It can affect the sensory quality of the wine with sweet/etherish properties. DHA can also react with proline to produce a "crust-like" aroma. Dihydroxyacetone can affect the anti-microbial activity in wine, as it has the ability to bind SO2.


References


External links


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{{Molecules detected in outer space Cosmetics chemicals Diols Alpha-hydroxy ketones Trioses