Dehydroascorbic acid (DHA) is an oxidized form of
ascorbic acid
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) an ...
(vitamin C). It is actively imported into the
endoplasmic reticulum
The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
of cells via glucose transporters.
[
] It is trapped therein by reduction back to ascorbate by
glutathione and other
thiols. The
(free) chemical radical semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
Structure and physiology
Top: ascorbic acid
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) an ...
( reduced form of vitamin C)
Bottom: dehydroascorbic acid
( nominal oxidized form of vitamin C)
Although a sodium-dependent transporter for
vitamin C exists, it is present mainly in specialized cells, whereas the
glucose transporters, the most notable being
GLUT1, transport Vitamin C (in its oxidized form, DHA)
in most cells, where recycling back to ascorbate generates the necessary enzyme cofactor and intracellular antioxidant, (see Transport to mitochondria).
The structure shown here for DHA is the commonly shown textbook structure. This 1,2,3-tricarbonyl is too electrophilic to survive more than a few milliseconds in aqueous solution, however. The actual structure shown by spectroscopic studies is the result of rapid
hemiketal
A hemiacetal or a hemiketal has the general formula R1R2C(OH)OR, where R1 or R2 is hydrogen or an organic substituent. They generally result from the addition of an alcohol to an aldehyde or a ketone, although the latter are sometimes called hemi ...
formation between the 6-OH and the 3-carbonyl groups. Hydration of the 2-carbonyl is also observed. The lifetime of the stabilized species is commonly said to be about 6 minutes under biological conditions.
[ Destruction results from irreversible hydrolysis of the ester bond, with additional degradation reactions following. Crystallization of solutions of DHA gives a pentacyclic dimer structure of indefinite stability. Recycling of ascorbate via active transport of DHA into cells, followed by reduction and reuse, mitigates the inability of humans to synthesize it from glucose.
]
Transport to mitochondria
Vitamin C accumulates in mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
, where most of the free radicals are produced, by entering as DHA through the glucose transporter GLUT10. Ascorbic acid protects the mitochondrial genome and membrane.[
]
Transport to the brain
Vitamin C does not pass from the bloodstream into the brain, although the brain is one of the organs that have the greatest concentration of vitamin C. Instead, DHA is transported through the blood–brain barrier
The blood–brain barrier (BBB) is a highly selective semipermeable membrane, semipermeable border of endothelium, endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of ...
via GLUT1 transporters, and then converted back to ascorbate.[
]
Use
Dehydroascorbic acid has been used as a vitamin C dietary supplement.
As a cosmetic ingredient, dehydroascorbic acid is used to enhance the appearance of the skin. It may be used in a process for permanent waving of hair[US Patent 6,506,373]
(issued January 14, 2003) and in a process for sunless tanning of skin.[U.S. Patent Application No. 10/685,073](_blank)
Publication No. 20100221203 (published September 2, 2010)
In a cell culture
Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...
growth medium
A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differen ...
, dehydroascorbic acid has been used to assure the uptake of vitamin C into cell types that do not contain ascorbic acid transporters.[
]
As a pharmaceutical agent, some research has suggested that administration of dehydroascorbic acid may confer protection from neuronal injury following an ischemic stroke.[
] Solutions in water containing ascorbic acid and copper ions and/or peroxide, resulting in rapid oxidation of ascorbic acid to dehydroascorbic acid, have been shown to possess powerful but short-lived antimicrobial, antifungal, and antiviral properties, and have been used to treat gingivitis, periodontal disease, and dental plaque.[Ericsson, Sten et al. "Anti Infectant Topical Preparations." U.S. Patent 3,065,139, filed November 9, 1954 and issued November 20, 1962]
/ref>[Fine, Daniel. "Gel composition for reduction of gingival inflammation and retardation of dental plaque." U.S Patent 5,298,237, filed Jan.24, 1992 and issued March 29, 1994]
/ref> A pharmaceutical product named Ascoxal is an example of such a solution used as a mouth rinse as an oral mucolytic and prophylactic agent against gingivitis.
References
Further reading
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External links
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{{Vitamin
Organic acids
Vitamin C
Diketones
de:Ascorbinsäure#Dehydroascorbinsäure