1.1 Vitamin C and its
The human body requires an ongoing amount of vitamin C
that is obtained through fruits and vegetables that are consumed. The intestinal tract is responsible for the absorption of vitamins,
restricting the amount that allowed to be absorbed so as to prevent an
excessively high level in the serum. At low doses nearly 100% of ingested
vitamin C is absorbed, although when an exceptionally high dose is ingested,
less than 50% is absorbed. Vitamin C is water soluble and any surplus is excreted in the urine (SF
Vitamin C is essential for the synthesis of collagen,
the primary structural protein found in the body. Collagen consists of amino
acids wound together to form triple-helices which form elongated fibrils that strengthen
connective tissue found in the tendons, ligaments and skin. There is research supporting evidence that vitamin C may
support bone health by stimulating the formation of collagen. According to a study
in Boston University, subjects who received less than 150 mg of vitamin C daily
experienced faster cartilage breakdown (ShareCare. 2013).
An important role of vitamin C is as an antioxidant,
which is a molecule capable of safely interacting with free radicals and
terminating the chain reaction that can result in vital molecules being harmed,
thus preventing the development of heart disease and other health conditions
such as cancer and arthritis. Vitamin C has been shown to boost immunity in the
body by stimulating both the production and function of white blood cells in
the body and through its antioxidant functions protects them from oxidative
damage taken when responding to invading microorganisms (Mercola. 2015).
History of Vitamin C
Vitamin C refers to both ascorbic acid and dehydroascorbic acid (DHA),
as both exhibit anti-ascorbic activity. Vitamin
C is one of the most important nutrients required by the human body on a daily
basis. It is a water soluble vitamin that is essential for all humans due to
the inability to biosynthesize the compound from glucose which would require
the enzyme gulunolactone oxidase, a key enzyme for
ascorbic acid biosynthesis (The National Academies Press. 2000).
The loss of activity of the gene
for L-gulolactone oxidase (GULO) in primates occurred approximately 63 million
years ago, splitting into the suborders Strepsirrhine primates, which are capable of producing their
own vitamin C,
and the Haplorhine primates, who must obtain it from their diets. The Haplorhini
subgroup containing the tarsiers and simians (apes, monkeys and humans). The Strepsirrhini
suborder of primates includes the lumuriform primates which consist of lemurs
from Madagascar, Galagos and Pottos from Africa and Lorises from India (Pollock, J. I. and Mullin,
R. J. (1987).
Vitamin C is a co-enzyme involved in the formation of
collagen, which is an essential protein in the formation of connective tissue.
A severe dietary deficiency of vitamin C in humans can result in a cease in biosynthesis
of collagen, resulting in a nutritional disease known as scurvy. Initial
manifestations of the disease are comprehensive, such as irritability, loss of
appetite, low grade fever and dermatological issues. The most noticeable of
symptoms however can be seen in the mouth when gums become swollen, loosen and
bleed on contact. When left untreated, scurvy can ultimately result in death
from infection or bleeding due to poor wound healing (Agawar, Anil et al. 2015).
One of the first accounts of scurvy can be dated back
to 1500 BC Egypt, where it is documented to have been treated with onions, a
common source of vitamin C. With the exception of this instance however, there
is very little documentation of scurvy until the age of sail or its treatment until
the mid 18th century. It was advances in naval technologies during
the age of sail making it possible for maritime explorers to extend their time
at sea and the food aboard ships being of poor nutritional value, often
entirely void of vitamin C and prone to spoilage, which caused scurvy to be a
tremendous problem (Jason Allen Mayberry. 2004). It was in 1753, on account of
the research of James Lind, that the British medical community accepted that a
deficiency in vitamin C was responsible for scurvy and that lime juice, leading
to the British being referred to as “limeys”, be carried on navy vessels.
Although Lind discovered the correlation between scurvy and a lack of fresh
fruit and vegetables, he was unaware of the specific component they contained
that was responsible for curing it (Bartholomew M. 2002).
Albert Szent-Gyorgyi, a Hungarian born scientist, is
responsible for the discovery of vitamin C in the 1930’s. In the course of his
studies when he isolated a molecule from adrenal glands that lost and regained
hydrogen atoms, exhibiting properties of both sugar and an acid. Szent-Gyorgyi
was then able to isolate the hexuronic-acid agent he believed responsible in citrus
juice for delaying the enzymatic browning of fruit that occurs when plants are
no longer able to produce enough hydrogen to prevent oxidation. Szent-Gyorgyi
and a vitamin researcher named J.L. Svirbely carried out an experiment to investigate
the effect of vitamin C on guinea pigs, which like humans require it to stay
healthy but cannot biosynthesize the compound within their bodies. The
experiment was divided into two groups, one of which would receive food which
had been boiled, thus destroying vitamin C, and the second group would receive
food enriched with hexuronic acid. While the first group deprived of vitamin C
developed the symptoms of scurvy and died, the second group which received
hexuronic acid thrived. To reflect its anti scurvy qualities it was renamed
ascorbic acid (Schultz. 2002). In 1933 Norman Haworth, a British Chemist, was
able to determine the molecular structure of vitamin C (Nobel Media Ab. 2014).
1.3 Physical and chemical properties
of vitamin C
Vitamin C, also known as ascorbic acid (see Figure 1.),
is physically described as white to slightly yellow crystals or powder that
gradually darken on exposure to light. It is odourless with a pleasant but
sharp acidic taste.
Vitamin C is a soluble vitamin, with 1g dissolving in
approx 3ml of water. It has a melting point of 190-192?C and releases acrid
smoke and irritating fumes when heated to decomposition.
Figure 1: Molecular Structure of vitamin C (ascorbic
Ascorbic acid is a reducing agent and a 6 carbon molecule.
Its molecular structure is C6H8O6 and has a molar mass of 176.12 g/mol (PubChem. 2016).