Dehydroascorbic acid (DHA) is the major oxidized form of ascorbic acid (vitamin C). It is actively imported into the endoplasmic reticulum of cells via glucose transporters. It is trapped therein by reduction back to ascorbic acid by glutathione and other thiols. The (free) chemical radical semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
Structure and physiology
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<div style="border: none; width:100px;"><div class="thumbcaption"><small>Top: ascorbic acid<br />(reduced form of vitamin C)<br />Bottom: dehydroascorbic acid<br />(nominal oxidized form of vitamin C)</small></div></div></div>
Although sodium-dependent transporters for vitamin C exists, it is present mainly in specialized cells whereas the glucose transporters, most notably GLUT1, transport DHA in most cells, The lifetime of the stabilized species is commonly said to be about 6 minutes under biological conditions. Crystallization of solutions of DHA gives a pentacyclic dimer structure of indefinite stability. Recycling of vitamin C via active transport of DHA into cells, followed by reduction and reuse, mitigates the inability of humans to synthesize it from glucose.
class=skin-invert-image|frame|none|link=|Hydration equilibria of DHA - center hemiketal structure is the predominant species in aqueous solutions.
Transport to mitochondria
Vitamin C accumulates in mitochondria, 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<!--keep this predicate PLURAL: subject-pronoun "that," whose antecedent is "organs," is PLURAL--> the greatest concentration of vitamin C. Instead, DHA is transported through the blood–brain barrier via GLUT1 transporters, and then reduced back to ascorbic acid.
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 and in a process for sunless tanning of skin.
In a cell culture growth medium, 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. and one study suggests dehydroascorbic acid has stronger antiviral effects and a different mechanism of action than ascorbic acid. 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. 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. Ascoxal solution has also been tested with positive results as a treatment for recurrent mucocutaneous herpes,