Uses of Ascorbic Acid: Overview, Questions, Preparation

Vitamin C, an organic compound, also referred to as ascorbic acid and chemically as hexuronic acid, is a water-soluble carbohydrate like a molecular compound that is widely known for its antioxidant properties and is also involved in some metabolic processes of animals. Most of the animals can synthesise their own ascorbic acid. Still, some mammals cannot, humans being one of them, as they lack the ability to synthesise ascorbate due to defective pseudogene (ψGULO) which codes for the enzyme L-gulonolactone oxidase, the final enzyme required for the synthesis of ascorbate. 

Since humans cannot synthesise ascorbic acid, they have a compensatory mechanism to recycle Vitamin C wherein ascorbic acid is oxidised to dehydroascorbic acid(DHA) which can be further reduced back to replenish ascorbic acid by an NADH system or by the action of Glutathione(GSH). This is of great importance in the erythrocytes as DHA is transported via GLUT1 transporters into the erythrocyte. It is immediately reduced to ascorbic acid, hence allowing the recycling of ascorbate. Ascorbic acid is essential for the maintenance of tissue and plasma reductive capacity to remove superoxide via its oxidation to ascorbic acid. 

Another function of ascorbic acid is in the hydroxylation of Proline to Collagen, where it acts as a cofactor. So, in a way, it is also necessary for bone remodelling because the organic matrix of the bone contains collagen.

Scurvy is a clinical condition of collagen deficiency, which in turn is caused by acute Vitamin C deficiency. It is characterised by haemorrhage that can occur in any organ, altered bone formation and brittle bones. Collagen type IV is the primary constituent of skin, blood vessel walls, and specifically, the basement membrane zone separating the epidermis from the dermis. Lack of Vitamin C decreases the transcription of pro-collagen and causes epigenetic DNA hypermethylation, which also inhibits the transcription of collagen found in skin, blood vessels, and tissues.

It is also involved in the synthesis of epinephrine from amino acid tyrosine. This hormone secreted by the medulla of the adrenal gland is responsible for increasing the cardiac output and raising the blood glucose level in humans. When depleted of ascorbate due to severe stress, the adrenal store requires ascorbate, which further plays a role in the synthesis of cortisol as well.

Hydroxylation of hypoxia-inducible factor 1α (HIF-1α) mediated by ascorbate regulates the transcription of genes encoding for proteins involved in angiogenesis, cell proliferation and iron homeostasis. Several studies have also shown that Vitamin C has some important role in vascular function. According to some studies, it is believed that Vitamin C appears to recycle tetrahydrobiopterin from its oxidised form, which further results in the synthesis of endothelial Nitric Oxide(eNO), which in turn generates NO, responsible for vasorelaxation.

Finally, apart from all these enzymatic processes, it is also a strong antioxidant with the ability to scavenge free radicals and reactive oxygen species. Vitamin C can also regenerate Vitamin E from its oxidised form, allowing Vitamin C to directly inhibit lipid peroxidation.

This topic is briefly discussed in a table under the chapter Acid, Bases and Salts.

This topic is briefly discussed in a table under the chapter Biomolecules, wherein its sources and deficiency diseases were discussed.

Q: What is the Chemical Formula of ascorbic acid?

Q: Is ascorbate the same as ascorbic acid?

Q: What are some of the rich natural sources of ascorbic acid?

Q: Various pathophysiology associated with Vitamin C or Ascorbic acid deficiency.

Q: Does Ascorbic acid decrease the ph of the stomach?