Chemical Properties
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.
Uses
Malic Acid is an acidulant that is the predominant acid in apples.
it exists as white crystalline powder or granules and is considered
hygroscopic. as compared to citric acid, it is slightly less soluble but
is still readily soluble in water with a solubility of 132 g/100 ml at
20°c. it has a stronger apparent acid taste and has a longer taste
retention than citric acid which peaks faster but does not mask the
aftertaste as effectively. a quantity of 0.362–0.408 kg of malic acid is
equivalent to 0.453 kg of citric acid and to 0.272–0.317 kg of fumaric
acid in tartness. at temperatures above 150°c it begins to lose water
very slowly to yield fumaric acid. it is used in soft drinks, dry-mix
beverages, puddings, jellies, and fruit filling. it is used in hard can-
dies because it has a lower melting point (129°c) than citric acid
which improves the ease of incorporation.
Uses
Malic acid, HOOCCH(OH).CH2COOH, also known as hydroxysuccinic acid, is a colorless solid. It is soluble in water and alcohol. Malic acid exists in two optically active forms and a racemic mixture. It is used in medicine and found in apples and other fruits.
The naturally occuring isomer is the L-form which has been found in apples and many other fruits and plants. Selective α-amino protecting reagent for amino acid derivatives. Versatile synthon for the preparation of chiral compounds including κ-opioid rece
Uses
malic acid is the third smallest alpha hydroxy acid in terms of molecular size. Although it is used in numerous cosmetic products, particularly those indicating a “fruit acid” content and generally designed for anti-aging, unlike glycolic and lactic acids, its skin benefits have not been extensively studied. Some formulators consider it difficult to work with, particularly when compared to other AHAs, and it can be somewhat irritating. It is rarely used as the only AHA in a product. It is found naturally occurring in apples.
Production Methods
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.
Definition
ChEBI: Malic acid is a 2-hydroxydicarboxylic acid that is succinic acid in which one of the hydrogens attached to a carbon is replaced by a hydroxy group. It has a role as a food acidity regulator and a fundamental metabolite. It is a 2-hydroxydicarboxylic acid and a C4-dicarboxylic acid. It derives from a succinic acid. It is a conjugate acid of a malate(2-) and a malate.
Biotechnological Production
DL-malic acid as well as L-malic acid can be used in beverage, food, and animal
nutrition. DL-malic acid is mainly derived from chemical synthesis, whereas L-malic
acid is produced biotechnologically by enzymatic or fermentative processes.
Fumaric acid can be converted to L-malic acid using fumarases. Different
microorganisms (e.g. Brevibacterium flavum, Brevibacterum ammoniagenes, and
Corynebacterium species) are able to form naturally high amounts of fumarase
intracellularly. For example, B. flavum has been immobilized in j-carrageenan
and polyethyleneimine for whole-cell biocatalysis. A fumarase activity of
2.16 mmol.ml(gel)-1.h -1 at 55 C has been reported. This process has been
used to produce 30 metric tons of L-malic acid per month in a continuous process
with a 1,000 L column fed at a flow rate of 450 L.h-1 of 1 M sodium fumarate
solution. Genetic engineering has been used to improve productivity, by
which S. cerevisiae is modified to overexpress fumarase. With this method, a
conversion rate of 65 mmol.g-1.h -1 has been observed.
Another possibility is the cultivation of an L-malic acid forming microorganism
(e.g. Aspergillus flavus or Schizophyllum commune). The best results have
been achieved by cultivation of A. flavus on glucose.Afinal product concentration of
113 g.L-1 with a yield of 1.26 mol of malic acid per mole of glucose and a productivity
of 0.59 g.L-1.h-1 has been measured. Moreover, new biotechnological
routes have been described using metabolically engineered S. cereviciae. In batch
cultivations, concentrations up to 59 g.L-1 with a yield of 0.42 mol of malic acid per
mole of glucose and a productivity of 0.19 g.L-1.h-1 have been observed.
General Description
The chiral resolution of DL-malic acid by ligand-exchange capillary electrophoresis was studied.
Flammability and Explosibility
Non flammable
Pharmaceutical Applications
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.
Biochem/physiol Actions
Malic acid is a dicarboxylic acid and an important regulatory metabolite. It has been implicated in process of fruit ripening. Malic acid is important for the starch metabolism; low malic acid content results in transient accumulation of starch. Mitochondrial-malate metabolism modulates ADP-glucose pyrophosphorylase activity and redox status of plastids.
Mechanism of action
Malic acid is absorbed from the gastrointestinal tract from whence it is transported via the portal circulation to the liver. There are a few enzymes that metabolize malic acid. Malic enzyme catalyzes the oxidative decarboxylation of L-malate to pyruvate with concomitant reduction of the cofactor NAD+ (oxidized form of nicotinamide adenine dinucleotide) or NADP+ (oxidized form of nicotinamide adenine dinucleotide phosphate). These reactions require the divalent cations magnesium or manganese. Three isoforms of malic enzyme have been identified in mammals: a cytosolic NADP+-dependent malic enzyme, a mitochondrial NADP+- dependent malic enzyme and a mitochondrial NAD(P)+-dependent malic enzyme. The latter can use either NAD+ or NADP+ as the cofactor but prefers NAD+. Pyruvate formed from malate can itself be metabolized in a number of ways, including metabolism via a number of metabolic steps to glucose. Malate can also be metabolized to oxaloacetate via the citric acid cycle. The mitochondrial malic enzyme, particularly in brain cells may play a key role in the pyruvate recycling pathway, which utilizes dicarboxylic acids and substrates, such as glutamine, to provide pyruvate to maintain the citric acid cycle activity when glucose and lactate are low.
Safety Profile
A poison by
intraperitoneal route. Moderately toxic by
ingestion. A skin and severe eye irritant.
When heated to decomposition it emits
acrid smoke and irritating fumes.
Safety
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.
LD
50 (rat, oral): 1.6 g/kg(3)
LD
50 (rat, IP): 0.1 g/kg
storage
Malic acid is stable at temperatures up to 150°C. At temperatures
above 150°C it begins to lose water very slowly to yield fumaric
acid; complete decomposition occurs at about 180°C 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.
The bulk material should be stored in a well-closed container, in
a cool, dry place.
Purification Methods
Crystallise the acid from acetone, then from acetone/CCl4, or from ethyl acetate by adding pet ether (b 60-70o). Dry it at 35o under 1mm pressure to avoid formation of the anhydride. [Beilstein 3 IV 1124.]
Incompatibilities
Malic acid can react with oxidizing materials. Aqueous solutions
are mildly corrosive to carbon steels.
Regulatory Status
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.
