Dehydroascorbic acid
Encyclopedia
Dehydroascorbic acid is an oxidized form of ascorbic acid
. It is actively imported into the endoplasmic reticulum
of cells via glucose transporters. It is trapped therein by reduction back to ascorbate by glutathione and other thiols. Therefore, L-dehydroascorbic acid is a vitamin C compound much like L-ascorbic acid. The (free) chemical radical
semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
of vitamin C)
Ascorbic acid
Ascorbic acid is a naturally occurring organic compound with antioxidant properties. It is a white solid, but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. Ascorbic acid is one form of vitamin C. The name is derived from a- and scorbutus , the...
. It is actively imported into the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
of cells via glucose transporters. It is trapped therein by reduction back to ascorbate by glutathione and other thiols. Therefore, L-dehydroascorbic acid is a vitamin C compound much like L-ascorbic acid. The (free) chemical radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
Structure and Physiology
(nominal oxidized formOxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...
of vitamin C)
Although there exists a sodium-dependent transporter for vitamin C
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
, it is mainly present in specialized cells, whereas the glucose transporter
Glucose transporter
Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Because glucose is a vital source of energy for all life these transporters are present in all phyla...
s, most notably GLUT1
GLUT1
Glucose transporter 1 , also known as solute carrier family 2, facilitated glucose transporter member 1 is a protein that in humans is encoded by the SLC2A1 gene...
, ensure in most cells of the body the transport of vitamin C (in its oxidized form, DHA) 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 hemiacetal 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, where most of the free radicals are produced, by entering as DHA through the glucose transporters, GLUT1. Ascorbic acid protects the mitochondrial genome and membrane.Transport to the brain
Vitamin C does not pass from the blood stream into the brainBrain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, although the brain is one of the organs which has the greatest concentration of vitamin C. Instead, DHA is transported through the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
via GLUT1 transporters
GLUT1
Glucose transporter 1 , also known as solute carrier family 2, facilitated glucose transporter member 1 is a protein that in humans is encoded by the SLC2A1 gene...
, and then converted back to ascorbate.
Use
As a dietary supplement, dehydroascorbic acid is found in some vitamin C tablets.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
Cell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
growth medium
Growth medium
A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....
, dehydroascorbic acid has been used to assure the uptake of vitamin C into cell types that do not contain ascorbic acid transporters. However that same study also indicated that unlike ascorbic acid (regular vitamin C), dehydroscorbic acid may promote rather than discourage cancer cell growth as one of it's experimental groups had increased cancer growth after dehydroscorbic acid treatment, but is the only known study with that outcome and the other dehydroscorbic groups in the study did not show that same effect.
As a pharmaceutical agent, some research has suggested that administration of dehydroascorbic acid may confer protection from neuronal injury following an ischemic stroke. The literature contains many reports on the antiviral effects of vitamin C, and one study suggests dehydroascorbic acid has stronger antiviral effects and a different mechanism of action than ascorbic acid.