Ascorbic acid occurs as a white to light-yellow-colored, nonhygroscopic, odorless, crystalline powder or colorless crystals with a sharp, acidic taste. It gradually darkens in color upon exposure to light.
BP: Ascorbic AcidJP: Ascorbic AcidPhEur: Ascorbic AcidUSP: Ascorbic Acid
Synonyms: Acidum ascorbicum; C-97; cevitamic acid; 2,3-didehydro-L-threohexono- 1,4-lactone; E300; 3-oxo-L-gulofuranolactone, enol form; vitamin C.
Chemical Name and CAS Registry Number
L-(þ)-Ascorbic acid [50-81-7]
Empirical Formula and Molecular Weight: C6H8O6 176.13
Functional Category: Antioxidant; therapeutic agent.
Applications in Pharmaceutical Formulation or Technology
Ascorbic acid is used as an antioxidant in aqueous pharmaceutical formulations at a concentration of 0.01–0.1% w/v. Ascorbic acid has been used to adjust the pH of solutions for injection, and as an adjunct for oral liquids. It is also widely used in foods as an antioxidant. Ascorbic acid has also proven useful as a stabilizing agent in mixed micelles containing tetrazepam.
Acidity/alkalinity: pH = 2.1–2.6 (5% w/v aqueous solution)Density (bulk): 0.7–0.9 g/cm3 for crystalline material; 0.5–0.7 g/cm3 for powder.Density (particle): 1.65 g/cm3Density (tapped): 1.0–1.2 g/cm3 for crystalline material; 0.9–1.1 g/cm3 for powder.Density (true): 1.688 g/cm3Dissociation constant: pKa1 = 4.17; pKa2 = 11.57.Melting point: 1908°C (with decomposition)Moisture content: 0.1% w/w
Method of Manufacture
Ascorbic acid is prepared synthetically or extracted from various vegetable sources in which it occurs naturally, such as rose hips, blackcurrants, the juice of citrus fruits, and the ripe fruit of Capsicum annuum L. A common synthetic procedure involves the hydrogenation of D-glucose to D-sorbitol, followed by oxidation using Acetobacter suboxydans to form L-sorbose. A carboxyl group is then added at C1 by air oxidation of the diacetone derivative of Lsorbose and the resulting diacetone-2-keto-L-gulonic acid is converted to L-ascorbic acid by heating with hydrochloric acid.