Dehydroascorbic acid (DHA) is the major oxidized form of
ascorbic acid
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent.
Asco ...
(vitamin C). It is actively imported into the
endoplasmic reticulum
The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...
of cells via glucose transporters.
[
] It is trapped therein by reduction back to ascorbic acid by
glutathione
Glutathione (GSH, ) is an organic compound with the chemical formula . It is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources ...
and other
thiols
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
. The
(free) chemical radical semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
Structure and physiology
Top: ascorbic acid
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent.
Asco ...
(reduced form In statistics, and particularly in econometrics, the reduced form of a simultaneous equations model, system of equations is the result of solving the system for the endogenous variables. This gives the latter as functions of the exogenous variables, ...
of vitamin C
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription di ...
)
Bottom: dehydroascorbic acid
( nominal oxidized form of vitamin C)
Although sodium-dependent transporters for
vitamin C
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription di ...
exists, it is present mainly in specialized cells whereas the
glucose transporter
Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose across the plasma membrane, a process known as facilitated diffusion. Because glucose is a vital source of energy for all life, these transporte ...
s, most notably
GLUT1
Glucose transporter 1 (or GLUT1), also known as solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1), is a uniporter protein that in humans is encoded by the ''SLC2A1'' gene. GLUT1 facilitates the transport of glucose acro ...
, transport DHA in most cells,
where recycling back to ascorbic acid 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
In organic chemistry, a hemiacetal is a functional group the general formula , where is a hydrogen atom or an organic substituent. They generally result from the nucleophilic addition of an alcohol (a compound with at least one hydroxy group) to ...
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 lactone bond, with additional degradation reactions following. 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.
]
Transport to mitochondria
Vitamin C accumulates in mitochondria
A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...
, where most of the free radical
A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing.
Ageing
Biogerontology
Biological processes
Causes of death
Cellular processes
Gerontology
Life extension
Metabolic disorders
Metabolism
...
s are produced, by entering as DHA through the glucose transporter GLUT10. Ascorbic acid protects the mitochondrial genome
Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in ...
and membrane
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...
.[
]
Transport to the brain
Vitamin C does not pass from the bloodstream into the brain
The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
, 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 regulates the transfer of solutes and chemicals between the circulatory system and the central nervous system ...
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[US Patent 6,506,373](_blank)
(issued January 14, 2003) and in a process for sunless tanning
Sunless tanning refers to the effect of a sun tanning, suntan without exposure to the Sun. Sunless tanning involves the use of #Oral agents, oral agents (carotenids), or creams, lotions or sprays applied to the skin. Skin-applied products may be ...
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 cell (biology), cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been Cell isolation, isolated from living tissue, ...
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''. Differe ...
, 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
Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop ...
.[
] 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
*
External links
*
{{Vitamin
Organic acids
Vitamin C
Diketones
Oxidizing agents
de:Ascorbinsäure#Dehydroascorbinsäure