The Vital Role and Emerging Discoveries of Vitamin C

Ascorbic acid, commonly known as vitamin C, is a crucial nutrient that supports the formation of intercellular substances in the human body. It plays an essential role in the development of dentine, cartilage, and the collagen matrix of bone. This makes it vital for tooth formation, fracture healing, and wound repair. Additionally, vitamin C is involved in oxidation-reduction reactions and contributes to the synthesis of certain hormones, supporting overall metabolic and immune functions.

A deficiency in vitamin C leads to scurvy, a disease marked by symptoms such as spongy gums, loose teeth, swollen joints, and bleeding in various tissues, as well as impaired wound healing. Fortunately, many foods offer substantial amounts of this nutrient. Citrus fruits, especially orange juice, remain one of the richest sources. Green vegetables like broccoli, cabbage, Brussels sprouts, and green peppers are also excellent sources, while tomatoes, peas, spinach, and lettuce contribute modest amounts.

Beyond human health, a 2007 study revealed vitamin C's essential role in plant growth. Researchers identified an enzyme that regulates ascorbic acid synthesis in response to light, with potential applications in agriculture and supplement production. This discovery may lead to genetically engineered microbes that can synthesize vitamin C more efficiently, replacing the current complex processes of fermentation and chemical synthesis with a streamlined one-step method.

Moreover, scientists at Johns Hopkins University demonstrated that vitamin C could inhibit the growth of certain tumors. Their findings suggest that antioxidants, rather than merely preventing oxidative stress, may disrupt cancer cell adaptation to low-oxygen environments. This insight opens new possibilities for enhancing the therapeutic use of antioxidants in cancer treatment.

Overall, vitamin C remains indispensable for both biological development and emerging biomedical applications.
The Vital Role and Emerging Discoveries of Vitamin C

The importance of ascorbic acid

Ascorbic acid was recognized as early as 1734 as the factor in fresh fruit and vegetables that prevent the development of scurvy.

Ascorbic acid or vitamin C is required for the formation of intercellular substances in the body, including dentine, cartilage, and the protein network or bone. Hence, it is important in tooth formation, the healing of broken bones, and the healing of wounds.

It may be important to oxidation –reduction reactions in the body and to the production of certain hormones.

In the brain, ascorbic acid may perform important functions related to the metabolism and release of several neurotransmitter.

Vitamin C is not only an important nutrient but is also used as an antioxidant in various foods.

Vitamin C recharges fat soluble vitamin E and water soluble glutathione, allowing them, to be reused many times.

Tomato juice, if it has been processed properly, is a fair source of this vitamin. Green peppers, cabbage, broccoli, and sprout are excellent to good sources of vitamin C, while other vegetables such as peas, spinach, and lettuce are good to fair sources. Many fruit contain fair amounts of vitamin C.

Overdoses of vitamin C induce perspiration, nervous tension, and lowered pulse rate.
The importance of ascorbic acid

The properties of vitamin C

Vitamin C is a small molecule, a white crystalline substance similar in structure to glucose. It is a highly polar, it is therefore soluble in aqueous conditions.

Vitamin C consists of a single molecule, called ascorbic acid or ascorbate, composed of six carbon atoms, six oxygen atoms, and eight hydrogen atoms, all linked to greater by chemical bonds.

Vitamin C is a water-soluble nutrient essential for life and is used by the human body for many purposes. The term vitamin C is generally used to describe all compounds that qualitatively exhibit the biological activity of ascorbate, including ascorbate and DHA.

All animals and plants synthesize their own vitamin C, except for a small number of animals, including guinea pigs, humans, apes, the red-vented bulbul, a fruit eating bat and a species of trout, that cannot.

Vitamin C is heat labile, and is destroyed by alkali solutions but stabilized by acid solution. It absorbs light whereupon it is destroyed.

The active part of the substance is the ascorbate ion, which can express itself as either an acid or a salt of ascorbate, that is neutral or slightly basic.

Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Absence of vitamin C causes scurvy, leading to spongy gums, loosed teeth, bruising, and bleeding into the mucous membranes.

The properties of vitamin C

The effects of ascorbic acid toxicity

Overdoses of vitamin C induce perspiration, nervous tension, and lowered pulse rate, WHO recommends that daily intake be less than 0.15 mg/kg.

Massive doses of vitamin C have been shown to reduce serum vitamin B12 levels. In part, this may be due to an effect of ascorbic acid on vitamin B12 in food.

Ascorbic acid destroys B12 in food. Ascorbic acid also inhibits the utilization of beta-carotene.

Some individuals, exhibit accelerated conversion of ascorbic acid to oxalate, probably through greater inducibility of enzymes in the ascorbate-oxalate pathway.

The hyperoxaluria of these individuals, following large doses of vitamin C, increases the risk of urinary stone formation.

Excessive doses of vitamin C can cause diarrhea but the effect is not long lasting. The large excess of vitamin C is promptly excreted in the urine but may cause uricosuria and increased absorption of iron, with the potential for iron reloaded.

Although toxicity is rare, the tolerable upper intake level established by the food and Nutrition Board (FNB) of the Institute of Medicine for vitamin C in adults was set at 2000 mg.
The effects of ascorbic acid toxicity

Absorption and Transport of Vitamin C

The ascorbic acid contained in foods appears to be readily available and absorbed.

Absorption of ascorbic acid in the intestine occurs through a sodium-dependent active transport system. But simple diffusion may also contribute somewhat to uptake of the vitamin.

The reduced and oxidized forms of the vitamin are absorbed by different mechanism of active transport:
*Ascorbic acid uptake by the sodium-dependent vitamin C transporter (SVCT)
*Dehydroascorbic acid uptake by glucose transporters (GLUT)

The transport of ascorbic acid into the ileum is a carrier-mediated process at low mucosal concentrations of ascorbic acid.

Absorption rate can vary from 16% at very high intakes (approximately 12g) to 98% at low intakes.

The degree of absorption as suggested by the urinary excretion of the vitamin appears to be adversely affected by pectin, zinc, copper, and iron.

From the intestinal cells, ascorbic acid diffuses through anion channels into extracellular fluid and enters the plasma by way of the capillaries.

At present it is unknown whether the decreased urinary ascorbic acid caused by the presence of the above three minerals reflects a less efficient absorption or an increased oxidation of the vitamin before it can be absorbed.

The cellular accumulations of vitamin C in humans are mediated by a variety of specific transporters located at the cell membranes and regulated in a cell-specific manner.

Absorbed ascorbic acid is transported in the plasma as a free anion. Normal plasma ascorbic acid concentrations range from about 0.4 to 1.7 mg/dL and it readily equilibrates with the body pool of the vitamin. The size of the pool therefore varies with the intake. Ascorbate moves freely into the cells, but the concentration is much greater in some tissues than in others.

The highest concentration of ascorbic acid are found in the adrenal and pituitary glands (with each possessing approximately 30-50 mg/100 g of wet tissue) as well as in the eyes, brain and white blood cells.

An intermediate level of the vitamin is found in the liver, lungs, pancreas and leukocytes, while smaller amounts occur in the kidneys muscles and red blood cells.

In absolute terms based on total weight, the liver contains the most ascorbic acid. The maximum pool is estimated at about 2g.
Absorption and Transport of Vitamin C

Toxicity of ascorbic acid

The amount of ascorbic acid in various tissues of the body varies markedly, probably depending on how those tissues use the ascorbic acid. It has been purported to be a prophylactic or treatment for the common cold as well as for cancer.

Ascorbic acid is a water-soluble vitamin and is not usually stored. Thus, there is little evidence of toxicity.

Still, many potentially harmful effects have been attributed to excessive intakes of ascorbic acid, but the frequency of recorded toxicity is quite low.

Excess ascorbic acid intakes in humans and laboratory animals have been reported to produce a variety of toxic signs or symptoms including allergic responses, oxaluria, uricosuria and interference with mixed- function oxidase systems.

Although some investigators have suggested that megadoses of ascorbic acid may be a risk factor in renal oxalate stores, urinary oxalate levels do not change with increasing intakes of ascorbate.

Ascorbic acid toxicity also found to produce rebound scurvy among infants and pregnant women.
Toxicity of ascorbic acid

Vitamin C: Function and Action

Vitamin C or L-ascorbic acid is chemically defined as 2-oxo-L-theo-hexono-4-lactone-2,3-enediol. Vitamin C is involved in many physiological functions in living organisms.

The only functional role of the vitamin to be categorically established is its ability to prevent and or cure scurvy. In this role, however, it must affect in some degree every bodily function because the vitamin is needed literally to hold the body’s cell together.

Additionally, the basement membrane lining the capillaries, the intracellular cement holding together the endothelial cells and the scar tissue responsible for wound healing all require the presence of vitamin C for their formation and maintenance.

Vitamin C is antioxidant and a cofactor in many hydroxylating reactions.  Leukocytes have high concentrations of ascorbate that is used rapidly during infection and phagocytosis, which points to vitamin C’s role in immunity.

Vitamin C is required in several reactions involved in body processes, including collagen synthesis, carnitine synthesis, tyrosine synthesis and catabolism, and neurotransmitter synthesis.
Vitamin C: Function and Action

The importance of ascorbic acid

The growing amount of published data on the physiological role of vitamin C represents a great variety of new aspects on the importance of this vitamin.

Ascorbic acid or vitamin C is required for the formation of intercellular substance in the body, including dentine, cartilage, and the protein network of bone.

Hence, it is important in tooth formation, the healing of broken bones, and the healing of the wounds. Vitamin C may be importance in the pathogenesis of most chronic diseases of aging.

Vitamin C has been found to be potentially important in the prevention of atherosclerosis, cancer, senile, cataract, lung diseases, cognitive function, and degenerative diseases of miscellaneous organs.

Deficiency of vitamin C cause scurvy (spongy gums, loose teeth, swollen joints, hemorrhages in various tissues, etc.) and impaired healing of wounds. Orange juice is an excellent source of vitamin C.

The best sources are fresh fruits particularly citrus fruits, tomatoes, and green peppers. Some fruits, like guava, and blackcurrants are particularly rich in the vitamin but they contribute little to normal Western dietary intake.

Green pepper, cabbage, broccoli, and Brussels sprouts are excellent to good sources of this vitamin C, while other vegetables such as peas, spinach, and lettuce are good to fair sources.

The term vitamin C comprises all compounds with the qualitative biological effect of L-ascorbic. L-ascorbic is a 2,3-enediol-L-gulonic acid.
The importance of ascorbic acid

Ascorbic acid as antioxidant

Ascorbic acid is a water soluble vitamin and has diverse functions in the body including as essential role in the hydroxylation reactions for the synthesis of collagen.

It is widely regarded as an essential antioxidant in the human body has even been called ‘the most important antioxidant in human plasma’.

Ascorbic acid’s function in food systems is complex and depends on a number of factors. Its antioxidants activity is affected by the oxidation-reduction potential of the food system, time, PH, oxygen, trace metals, enzymes, other oxidants, and the concentration of the vitamin in comparison to the concentration of other reactants in the oxidation process.

Antioxidant can be defined as any substance that when present at low concentration compared to those of an oxidizable substrate, significantly delays or prevents oxidation of that substrate.

In-vitro experiments have shown that ascorbic acid can act as a chain breaking antioxidant in lipid peroxidation. Studies of the antioxidant activity of human blood plasma suggest that ascorbic acid is the major extracellular antioxidant.

As an oxygen scavenger, ascorbic acid also serves as a reducing agent. It transfers its hydrogen atoms to oxygen, making the oxygen unavailable for further reaction. In the process, the ascorbic acid is oxidized to dehydroascorbic acid, which in turn can function as an oxidizing agent by removing hydrogen from reducing agents such as sulfhydryl groups.

Ascorbic acid and dehydroascorbic acid are thus reversible forms of vitamin C and both have physiological activity. Further, ascorbic acid may exert a chelating action, binding heavy chemical, if present will promote oxidation. When chelated with heavy metals, ascorbic acid loses its physiological vitamin activity.

Ascorbic acid can also undergo autoxidative destruction especially in the presence of transition metals such as copper and iron, which in turn promotes and accelerates the autoxidation of other macromolecules such as unsaturated lipids.

Ascorbic acid is widely used as an oxygen scavenger and synergist in numerous food applications and has a higher oxidation potential (greater reducing capacity) than most phenolic antioxidants.
Ascorbic acid as antioxidant

Scurvy and vitamin C

Vitamin C is a water soluble known as ascorbic acid. It is a six carbon lactone. This vitamin is involved in collagen synthesis, acts as an antioxidant and aids iron absorption. Collagen is an important structural component of blood vessel, tendons, ligaments and bone.

Vitamin C also plays an important role in the synthesis of the neurotransmitter, norepinephrine.

Scurvy is a disease of vitamin C. The early symptoms are weakness, fatigue, listlessness and lassitude. The name given to set of symptoms that develop during a severe long-term shortage of vitamin C. 

It can result in bleeding into the joints causing haemarthrosis: swelling and pain at the join, Trauma is one of the most frequent causes of haemarthrosis but in scurvy bleeding can occur in the absent of trauma.

Although scurvy is extremely rare, doctors still see an occasional case. Historically the source of scurvy was described by Hippocrates documented during the Crusades and recognized as an occupational hazard among naval officers and pirates alike.

By late 1700s the British navy were aware that scurvy could be cured by eating oranges or lemons, even though vitamin C would not be isolated until the early 1930s.
Scurvy and vitamin C

Discovery of vitamin C

Another name for vitamin C that derives from the Latin word ascorbic, which means ‘without scurvy’. Discovery of vitamin C is one of the biggest achievements in biochemical area. It was discovered by novel prize winner Albert Szent-Gyorgyi in 1928.

In that year Szent-Gyorgyi isolated hexuronic acid as the factor that prevented browning of decaying fruit. In 1932 it was proved to be the agent which prevents scurvy.

Written records dating back to ancient Egypt containing the earliest reports of scurvy, a dreaded human disease caused by vitamin C deficiency. Scurvy has remained constant threat to humans, causing death and misery whenever dietary sources of vitamin C became scarce.

Aristotle in 450 BC described the symptoms of scurvy, which include muscle weakness, lethargy, extreme fatigue, joint pains, bleeding gums, depression and eventually death.

During the 17th and early 18th centuries, many cures for scurvy were suggested and there was some evidence that fresh fruit could help.

In 1747, Dr. James Lind discovered that adding citrus fruit to the diet will helped prevent scurvy.

The popularity do vitamin C as one of the most widely used and highly valued vitamin began when Dr. Linus Pauling proposed in 1970 that the daily intake of vitamin C needs to be much higher than the official recommended daily intake of 60mg per day. He published his book in vitamin C: Vitamin C and the Common Cold.

Discovery of vitamin C 

Ascorbic Acid in general

Ascorbic acid was recognized as early as 1734 as the factor in fresh fruit and vegetables that prevent the development of scurvy.

Vitamin C has been implicated in the hydroxylation of proline to form the hydroxyproline required in the formation of collagen.

It helps in the healing of wounds fractures, bruises and bleeding, gums and recues liability the infection.

Excellence sources of vitamin C are citrus fruits, berries, guava, capsicum and green leafy vegetables. Tomato juice, if it has been processed properly, is a fair source of this vitamin. Green peppers, cabbage, broccoli, and sprout are excellent to good sources of vitamin C.

Deficiency of vitamin C causes scurvy (spongy gums, loose teeth, swollen joints, hemorrhages in various tissue, etc) and impaired healing of wounds. Orange juice is an excellent source of vitamin C.
Ascorbic Acid