An essential nutrient for humans.
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 ("vitamer")
of vitamin C. It was originally called L-hexuronic acid,
but when it was found to have vitamin C activity in animals
("vitamin C" being defined as a vitamin activity,
not then a specific substance), the suggestion was made
to rename L-hexuronic acid. The new name for L-hexuronic
acid is derived from a- (meaning "no") and scorbutus
(scurvy), the disease caused by a deficiency of vitamin
C. Because it is derived from glucose, many animals are
able to produce it, but humans require it as part of their
nutrition. Other vertebrates lacking the ability to produce
ascorbic acid include other primates, guinea pigs, teleost
fishes, bats, and birds, all of which require it as a dietary
micronutrient (that is, a vitamin).
Chemically, there exists a D-ascorbic acid which does not
occur in nature. It may be synthesized artificially. It
has identical antioxidant properties to L-ascorbic acid,
yet has far less vitamin C activity (although not quite
zero).. This fact is taken as evidence that the antioxidant
properties of ascorbic acid are only a small part of its
effective vitamin activity. Specifically, L-ascorbate is
known to participate in many specific enzyme reactions which
require the correct epimer (L-ascorbate and not D-ascorbate)."
C or L-ascorbic acid, or simply ascorbate (the anion of
ascorbic acid), is an essential nutrient for humans and
certain other animal species. Vitamin C refers to a number
of vitamers that have vitamin C activity in animals, including
ascorbic acid and its salts, and some oxidized forms of
the molecule like dehydroascorbic acid. Ascorbate and ascorbic
acid are both naturally present in the body when either
of these is introduced into cells, since the forms interconvert
according to pH.
Vitamin C is a cofactor in at least eight enzymatic reactions
including several collagen synthesis reactions that, when
dysfunctional, cause the most severe symptoms of scurvy.
In animals, these reactions are especially important in
wound-healing and in preventing bleeding from capillaries.
Ascorbate may also act as an antioxidant against oxidative
stress. However, the fact that the enantiomer D-ascorbate
(not found in nature) has identical antioxidant acivity
to L-ascorbate, yet far less vitamin activity, underscores
the fact that most of the function of L-ascorbate as a vitamin
relies not on its antioxidant properties, but upon enzymic
reactions that are stereospecific. "Ascorbate"
without the letter for the enantiomeric form is always presumed
to be the chemical L-ascorbate.
Ascorbate (the anion of ascorbic acid) is required for
a range of essential metabolic reactions in all animals
and plants. It is made internally by almost all organisms
although notable mammalian group exceptions are most or
all of the order chiroptera (bats), guinea pigs, capybaras,
and one of the two major primate suborders, the Anthropoidea
(i.e., Haplorrhini, consisting of tarsiers, monkeys and
apes, including human beings). Ascorbate is also not synthesized
by some species of birds and fish. All species that do not
synthesize ascorbate require it in the diet. Deficiency
in this vitamin causes the disease scurvy in humans.
Ascorbic acid is also widely used as a food additive, to
prevent oxidation." http://en.wikipedia.org/wiki/Vitamin_C