Name: Malic Acid
CAS No: Hydroxybutanedioic acid [6915-15-7], (RS)-()-Hydroxybutanedioic acid [617-48-1]
BP: Malic Acid PhEur: Malic Acid USP-NF: Malic Acid
Acidum malicum; apple acid; E296; 2-hydroxy-1,4-butanedioic acid; hydroxybutanedioic acid; 1-hydroxy-1,2-ethanedicarboxylic acid; hydroxysuccinic acid; 2-hydroxysuccinic acid; DL-malic acid.
Hydroxybutanedioic acid [6915-15-7], (RS)-()-Hydroxybutanedioic acid [617-48-1]
C4H6O5 134.09
Malic acid is used in pharmaceutical formulations as a generalpurpose acidulant. It possesses a slight apple flavor and is used as a flavoring agent to mask bitter tastes and provide tartness. Malic acid is also used as an alternative to citric acid in effervescent powders, mouthwashes, and tooth-cleaning tablets. In addition, malic acid has chelating and antioxidant properties. It may be used with butylated hydroxytoluene as a synergist in order to retard oxidation in vegetable oils. In food products it may be used in concentrations up to 420 ppm. Therapeutically, malic acid has been used topically in combination with benzoic acid and salicylic acid to treat burns, ulcers, and wounds. It has also been used orally and parenterally, either intravenously or intramuscularly, in the treatment of liver disorders, and as a sialagogue.(1)
White or nearly white, crystalline powder or granules having a slight odor and a strongly acidic taste. It is hygroscopic. The synthetic material produced commercially in Europe and the USA is a racemic mixture, whereas the naturally occurring material found in apples and many other fruits and plants is levorotatory.
See Table I.
Data shown below are for the racemate. See Section 17 for other data for the D and L forms. Acidity/alkalinity pH = 2.35 (1% w/v aqueous solution at 258C) Boiling point 1508C (with decomposition) Density (bulk) 0.81 g/cm3 Density (tapped) 0.92 g/cm3 Dissociation constant pKa1 = 3.40 at 258C; pKa2 = 5.05 at 258C. Melting point 131–1328C NIR spectra see Figure 1. Solubility Freely soluble in ethanol (95%) and water but practically insoluble in benzene. A saturated aqueous solution contains about 56% malic acid at 208C. See Table II. Specific gravity 1.601 at 208C; 1.250 (saturated aqueous solution at 258C). Viscosity (dynamic) 6.5 mPa s (6.5 cP) for a 50% w/v aqueous solution at 258C
Malic acid is stable at temperatures up to 1508C. At temperatures above 1508C it begins to lose water very slowly to yield fumaric acid; complete decomposition occurs at about 1808C to give fumaric acid and maleic anhydride. Malic acid is readily degraded by many aerobic and anaerobic microorganisms. Conditions of high humidity and elevated temperatures should be avoided to prevent caking. The effects of grinding and humidity on malic acid have also been investigated.(2) The bulk material should be stored in a well-closed container, in a cool, dry place.
Malic acid can react with oxidizing materials. Aqueous solutions are mildly corrosive to carbon steels.
Malic acid is manufactured by hydrating maleic and fumaric acids in the presence of suitable catalysts. The malic acid formed is then separated from the equilibrium product mixture.
Malic acid is used in oral, topical, and parenteral pharmaceutical formulations in addition to food products, and is generally regarded as a relatively nontoxic and nonirritant material. However, concentrated solutions may be irritant. LD50 (rat, oral): 1.6 g/kg(3) LD50 (rat, IP): 0.1 g/kg
Observe normal precautions appropriate to the circumstances and quantity of material handled. Malic acid, and concentrated malic acid solutions may be irritant to the skin, eyes, and mucous membranes. Gloves and eye protection are recommended.
GRAS listed. Both the racemic mixture and the levorotatory isomer are accepted as food additives in Europe. The DL and L forms are included in the FDA Inactive Ingredients Database (oral preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Nonmedicinal Ingredients
Citric acid; fumaric acid; D-malic acid; L-malic acid; tartaric acid. D-Malic acid Empirical formula C4H6O5 Molecular weight 134.09 CAS number [636-61-3] Synonyms (R)-(þ)-Hydroxybutanedioic acid; D-(þ)-malic acid. Melting point 99–1018C Specific rotation [a]D 20 = þ5.28 (in acetone at 188C). L-Malic acid Empirical formula C4H6O5 Molecular weight 134.09 CAS number [97-67-6] Synonyms Apple acid; (S)-(–)-hydroxybutanedioic acid; L-(–)- malic acid. Boiling point 1408C (with decomposition) Melting point 99–1008C Solubility Practically insoluble in benzene. See also Table III. Specific gravity 1.595 at 208C Specific rotation [a]D 20 = 5.78 (in acetone at 188C)
A specification for malic acid is contained in the Food Chemical Codex (FCC).(4) The EINECS number for malic acid is 202-601-5. The PubChem Compound ID (CID) for malic acid is 525.