The pharmacophore of vitamin C is the ascorbate ion. In living organisms, ascorbate is an anti-oxidant, since it protects the body against oxidative stress, and is a cofactor in several vital enzymatic reactions.
Scurvy has been known since ancient times. People in many parts of the world assumed it was caused by a lack of fresh plant foods. The British Navy started giving sailors lime juice to prevent scurvy in 1795. Ascorbic acid was finally isolated in 1933 and synthesized in 1934. The uses and recommended daily intake of vitamin C are matters of on-going debate, with RDI ranging from 45 to 95 mg/day. Proponents of megadosage propose from 200 to upwards of 2000 mg/day. A recent meta-analysis of 68 reliable antioxidant supplementation experiments, involving a total of 232,606 individuals, concluded that consuming additional ascorbate from supplements may not be as beneficial as thought.
DeficiencyScurvy is an avitaminosis resulting from lack of vitamin C, since without this vitamin, the synthesised collagen is too unstable to perform its function. Scurvy leads to the formation of liver spots on the skin, spongy gums, and bleeding from all mucous membranes. The spots are most abundant on the thighs and legs, and a person with the ailment looks pale, feels depressed, and is partially immobilized. In advanced scurvy there are open, suppurating wounds and loss of teeth and, eventually, death. The human body can store only a certain amount of vitamin C, and so the body soon depletes itself if fresh supplies are not consumed.
It has been shown that smokers who have diets poor in vitamin C are at a higher risk of lung-borne diseases than those smokers who have higher concentrations of vitamin C in the blood.
Nobel prize winner Linus Pauling and Dr. G. C. Willis have asserted that chronic long term low blood levels of vitamin C or Chronic Scurvy is a cause of atherosclerosis.
Western societies generally consume sufficient Vitamin C to prevent scurvy. In 2004 a Canadian Community health survey reported that Canadians of 19 years and above have intakes of vitamin C from food of, 133 mg/d for males and 120 mg/d for females, which is higher than the RDA recommendation.
Physiological functionIn humans, vitamin C is essential to a healthy diet as well as being a highly effective antioxidant, acting to lessen oxidative stress; a substrate for ascorbate peroxidase; and an enzyme cofactor for the biosynthesis of many important biochemicals. Vitamin C acts as an electron donor for important enzymes: Collagen, carnitine, and tyrosine synthesis, and microsomal metabolism.
AntioxidantAscorbic acid is well known for its antioxidant activity. Ascorbate acts as a reducing agent to reverse oxidation in aqueous solution. When there are more free radicals (Reactive oxygen species) in the body versus antioxidant, a human is under the condition called Oxidative stress. Oxidative stress induced diseases encompass cardiovascular diseases, hypertension, chronic inflammatory diseases and diabetes. The plasma ascorbate concentration in oxidative stress patient (less than 45 µmol/L) measured is lower than healthy individual (61.4-80 µmol/L) According to McGregor and Biesalski. increasing plasma ascorbate level may have therapeutic effects in oxidative stress individual. Individuals with oxidative stress and healthy individuals have different pharmacokinetics of ascorbate.
|< Prev||Next >|