Ascorbic acid

• BPAscorbic Acid
• JPAscorbic Acid
• Ph. Eur.Ascorbic Acid
• USP–NFAscorbic Acid

Acidum ascorbicum; L-ascorbic acid; 3-oxo-L-gulofuranolactone (enol form); vitamin C; E300

(5R)-5-[(1S)-1,2-Dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one · [50-81-7]

UNII PQ6CK8PD0R · PubChem CID 54670067

C6H8O6 · 176.13

Antioxidant, chelating agent

Typical concentrations: — · Dosage forms: Liquid, Sterile (parenteral/ophthalmic), Solid

Used as a water-soluble antioxidant in aqueous oral, parenteral and topical preparations, typically at 0.01–0.1% w/v, and as an acidifying agent. It acts synergistically with chelating agents and with lipophilic antioxidants such as tocopherols. It is also widely used as a food antioxidant and is the active form of vitamin C.

White or slightly yellow, odourless crystals or crystalline powder with a pleasant, sharp acidic taste. It gradually darkens on exposure to light.

Melting point

≈ 190–192 °C, with decomposition

pKa

pKa1 ≈ 4.2; pKa2 ≈ 11.6

pH

about 2.1–2.6 (5% w/v aqueous solution)

Specific rotation

+20.5° to +21.5° (10% w/v in water)

Solubility

freely soluble in water (about 1 in 3.5); sparingly soluble in ethanol; practically insoluble in ether, chloroform and fixed oils

Reasonably stable in dry air, but in solution it is rapidly oxidised, especially at neutral to alkaline pH and in the presence of copper, iron and other metal ions; light and heat also accelerate degradation. Store in an airtight, non-metallic container protected from light in a cool, dry place. Solutions should be made with deoxygenated water and may be protected with a chelating agent and an inert gas headspace.

Incompatible with alkalis, heavy-metal ions (especially copper and iron), oxidising agents, methenamine, phenylephrine hydrochloride, pyrilamine maleate, salicylamide, sodium nitrite, sodium salicylate and theobromine salicylate. As a reducing agent it can reduce some drugs and dyes.

Made from glucose via sorbitol and sorbose (the Reichstein process), or by more modern two-step fermentation processes that convert sorbitol to 2-keto-L-gulonic acid, which is then converted chemically to ascorbic acid and purified by crystallisation.

An essential nutrient, well tolerated at excipient levels. Large oral doses can cause gastrointestinal upset and diarrhoea and may increase urinary oxalate, with a risk of renal stones in predisposed people. JECFA has allocated an ADI 'not specified'.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended; the dust may irritate the eyes.

GRAS listed. Accepted as a food additive in Europe (E300). Included in the FDA Inactive Ingredient Database (inhalation, injections, oral and topical preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Ascorbyl palmitate; erythorbic acid; sodium ascorbate; calcium ascorbate.

Ascorbic acid protects formulations by being oxidised preferentially, so it is consumed over the shelf-life; its degradation products can discolour solutions yellow or brown. The pH of the formulation strongly influences its stability, which is best in mildly acidic conditions.