Fumaric acid

• USP–NFFumaric Acid

Allomaleic acid; boletic acid; (E)-butenedioic acid; trans-butenedioic acid; lichenic acid; E297

(E)-Butenedioic acid · [110-17-8]

UNII 88XHZ13131 · PubChem CID 444972

C4H4O4 · 116.07

pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Solid

Used as an acidulant and flavouring agent in foods, beverages and oral pharmaceutical preparations, and as the acid component of effervescent tablets, where its low hygroscopicity is an advantage. It is also used as a pH modifier in solid dosage forms to improve the release of weakly basic drugs, and as the counter-ion for fumarate salts of drugs. It is used at the levels needed to achieve the required acidity or pH.

The trans isomer of butenedioic acid and a normal intermediate of the citric acid cycle. White, odourless or almost odourless granules or crystalline powder with a strongly acidic, fruit-like taste.

pKa

pKa1 ≈ 3.0; pKa2 ≈ 4.4

Melting point

about 287 °C in a sealed tube; sublimes at about 200 °C

Solubility

slightly soluble in water (about 0.6–0.7 g per 100 mL at 25 °C); soluble in ethanol; slightly soluble in ether

Hygroscopicity

non-hygroscopic

Stable and not hygroscopic. Store in a well-closed container in a cool, dry place.

Reacts with bases and with carbonates and bicarbonates (with release of carbon dioxide). Incompatible with strong oxidising agents.

Made mainly by catalytic isomerisation of maleic acid, obtained from maleic anhydride produced by oxidation of butane or benzene. It can also be produced by fermentation, for example with Rhizopus species.

As a normal metabolic intermediate, fumaric acid is of low oral toxicity at the levels used in foods and medicines. The concentrated powder and its solutions can irritate the eyes, skin and respiratory tract.

Observe normal precautions for the quantity handled. Eye protection, gloves and, where dust is generated, a dust mask are recommended.

Permitted as a direct food additive in the USA. Accepted as a food additive in Europe (E297) and evaluated by JECFA. Included in the FDA Inactive Ingredient Database (oral preparations).

Citric acid; malic acid; maleic acid; tartaric acid.

Its low water solubility gives a slow, sustained acidifying effect, which is useful as a microenvironmental pH modifier but makes it react more slowly than citric acid in effervescent systems; it is often combined with more soluble acids for that purpose.