Chemistry of ascorbic acid organic acids as an alcohol forming esters such as ascorbyl palmitate and ascorbyl stearate. Nucleophilic attack of ascorbic acid on a proton results in a 1,3-diketone: The ascorbate ion is the predominant species at typical biological pH values. It is a mild reducing agent and antioxidant. It is oxidized with loss of one electron to form a radical cation and then with loss of a second electron to form dehydroascorbic acid. It typically reacts with oxidants of the reactive oxygen species, such as the hydroxyl radical. Ascorbic acid is special because it can transfer a single electron, owing to the
Vitamin C and also regenerator of other antioxidants. Plants use multiple pathways to synthesize vitamin C. The major pathway starts with glucose, fructose or mannose (all simple sugars) and proceeds to L-galactose, L-galactonolactone and ascorbic acid. There is feedback regulation in place, in that the presence of ascorbic acid inhibits enzymes in the synthesis pathway. This process follows a diurnal rhythm, so that enzyme expression peaks in the morning to support biosynthesis later on when mid-day sunlight intensity demands high ascorbic acid concentrations. Minor pathways may be specific to certain parts of plants; these can be either identical to the vertebrate pathway