Ascorbic acid (vitamin C) is a water-soluble vitamin. It occurs as a white or slightly yellow crystal or powder with a slight acidic taste. Ascorbic acid is an electron donor, and this property accounts for all its known functions. As an electron donor, ascorbic acid is a potent water-soluble antioxidant in humans. Ascorbic acid acts as an antioxidant under physiologic conditions exhibiting a cross over role as a pro-oxidant in pathological conditions. Oxidized ascorbic acid (dehydroascorbic acid (DHA) directly inhibits IkappaBalpha kinase beta (IKKbeta) and IKKalpha enzymatic activity in vitro, whereas ascorbic acid did not have this effect. These findings define a function for vitamin C in signal transduction other than as an antioxidant and mechanistically illuminate how vitamin C down-modulates NF-kappaB signaling. Vitamin C is recommended for the prevention and treatment of scurvy. Its parenteral administration is desirable for patients with an acute deficiency or for those whose absorption of orally ingested ascorbic acid (vitamin c) is uncertain. Symptoms of mild deficiency may include faulty bone and tooth development, gingivitis, bleeding gums, and loosened teeth. Febrile states, chronic illness, and infection (pneumonia, whooping cough, tuberculosis, diphtheria, sinusitis, rheumatic fever, etc.) increase the need for ascorbic acid (vitamin c). Hemovascular disorders, burns, delayed fracture and wound healing are indications for an increase in the daily intake.

Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid. Ascorbic acid is transported in its oxidized form via GLUT1 across the blood-brain barrier. Dehydroascorbic acid delay low-density lipoprotein (LDL) oxidation when added before the initiation of the process, they accelerate the process if added to minimally oxidized LDL. Dehydroascorbic acid is used as biochemical markers of oxidative stress in clinical investigations. Dehydroascorbic acid has been used as a vitamin C dietary supplement.

Ascorbyl gamolenate, an aldehyde reductase inhibitor, participated in phase-I clinical trials for Diabetic neuropathies in the United Kingdom but these studies were discontinued.