Maleic acid does not have a specific pharmacological target as a therapeutic agent. Instead, it is primarily used as a pharmaceutical excipient and chemical intermediate. Maleic acid forms maleate salts with basic drugs, improving their aqueous solubility, stability, and oral bioavailability. It is also used in the production of various polymers, resins, and agrochemicals. Maleic acid has mild antimicrobial properties.

WT 10403S has MICs of 34 mM, 25 mM, 31 mM, and 30 mM against acids (such maleic acid), which translate to pre-growth pH values of 4.84, 5.14, 5.32, and 5.02, in that order. Maleic acid, which functions at a lower pH (4.84), exhibited the least inhibitory effect of all the chemicals examined. At pH 3, 8.6 mM and 4.3 mM of each organic acid were given to the strains that were the least acid-tolerant (EGD-e) and the most acid-tolerant (10403S), respectively. Maleic acid had the greatest bactericidal effect on these two strains [2].
In vitro, maleic acid has been shown to exhibit mild antimicrobial activity against certain microorganisms. Its primary pharmaceutical application is as a salt-forming agent to improve the solubility and stability of basic drugs. Maleic acid's ability to form stable salts with amine-containing drugs is well characterized. The compound is also used as a standard in various biochemical assays.

In vivo, maleic acid is metabolized through the citric acid cycle and is excreted as carbon dioxide and water. As a pharmaceutical excipient, it is generally considered safe at the concentrations used in drug formulations. Maleic acid is not used as a therapeutic drug but rather as an excipient to improve drug properties.

In non-cell-based biochemical assays, maleic acid is used as a standard or reagent. Its properties as a dicarboxylic acid are characterized using standard chemical analysis methods. The compound may be evaluated for its antimicrobial activity using standard susceptibility testing methods. However, these assays are not typically performed as maleic acid is not primarily used as a bioactive agent.

In vitro cellular assays for maleic acid are not commonly performed as the compound is primarily used as a pharmaceutical excipient and chemical intermediate. When evaluated, its effects on cell viability and proliferation may be assessed to confirm its safety as an excipient. However, these assays are not typically required for its approved uses.

In vivo animal studies for maleic acid have been conducted to establish its safety as a pharmaceutical excipient. These studies have shown that maleic acid is well-tolerated at the concentrations used in drug formulations. The compound is metabolized and excreted through normal metabolic pathways.

Maleic acid is absorbed and metabolized in the body. It enters the citric acid cycle and is ultimately converted to carbon dioxide and water. The compound has a relatively short half-life and is rapidly eliminated. Its pharmacokinetic properties support its use as a pharmaceutical excipient.

Maleic acid is generally considered safe as a pharmaceutical excipient and food additive at typical concentrations. However, at high concentrations, it can cause irritation to the skin, eyes, and respiratory tract. The compound should be handled with appropriate safety precautions, including the use of personal protective equipment and adequate ventilation.

[1]. Glutamate decarboxylase. Substrate specificity and inhibition by carboxylic acids. Biochemistry. 1972 Mar 28;11(7):1304-9.

[2]. A novel approach in acidic disinfection through inhibition of acid resistance mechanisms; Maleic acid-mediated inhibition of glutamate decarboxylase activity enhances acid sensitivity of Listeria monocytogenes. Food Microbiol. 2018 Feb;69:96-104.

Maleic acid is a colorless crystalline solid with a slight odor. It is flammable, but requires some effort to ignite. It is soluble in water. It is used in the manufacture of other chemicals and in the dyeing and finishing of natural fibers. Maleic acid is a butenedioic acid with a cis (Z) configuration of its double bonds. It is a plant metabolite, an algal metabolite, and a mouse metabolite. It is the conjugate acid of maleate (1-) and maleate. Maleic acid has been reported to be found in European aspen (Populus tremula), spotted madder (Psychotria punctata), and several other organisms with relevant data. Maleic acid is an organic salt or ester of maleic acid that can be combined with free base compounds/drugs to improve its physicochemical properties, including stability, solubility, and dissolution rate. (NCI) Maleic acid is an industrial feedstock for the ozone decomposition process to produce glyoxylic acid. Maleic acid is an organic compound belonging to the dicarboxylic acid family (containing two carboxyl groups in the molecule). The molecule consists of one vinyl group and two carboxyl groups. Maleic acid is the cis isomer of butenic acid, while fumaric acid is its trans isomer. The cis isomer is less stable, and their heats of combustion differ by 22.7 kJ/mol. The physical properties of maleic acid are drastically different from those of fumaric acid. Maleic acid is soluble in water, while fumaric acid is insoluble; the melting point of maleic acid (130-131°C) is also much lower than that of fumaric acid (287°C). These properties of maleic acid can be attributed to the formation of intramolecular hydrogen bonds, which weaken intermolecular interactions. Maleic acid undergoes dehydration to produce maleic anhydride, hydration to produce malic acid, and hydrogenation to produce succinic acid. It reacts with thionyl chloride or phosphorus pentachloride to produce maleyl chloride (which cannot be isolated to obtain monoacyl chloride). Maleic acid is a reactant in many Diels-Alder reactions. See also: Surfactants (monomers); Iron polymers (monomers)... See more...

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Mechanism of Action
Systemic toxicity of maleic acid has been observed to cause kidney damage. Intraperitoneal injection (100–350 mg/kg; rats, dogs) and inhalation of approximately 720 mg/mc (rat) both caused morphological and functional changes in the kidneys. Damage to distal and proximal tubular reabsorption caused by maleic acid is similar to known (congenital or acquired) Fanconi syndrome in humans. This damage appears to be caused by the interaction of maleic acid with glutathione in renal tubular cells, leading to excessive concentrations of free radicals and peroxides. In addition to the resulting cellular damage, maleic acid appears to affect Na+ and H+ ion transport in the proximal tubules [RE5]. In male rats, prolonged exposure to maleic acid (250, 500, 750 mg/kg/day for up to two years) resulted in increased mortality, kidney damage, and growth retardation in all dose groups. Liver and testicular damage were also observed in the highest dose group. No carcinogenic activity of maleic acid was found with long-term administration, but this study was not intended to conduct a carcinogenicity study.
Maleic acid is a dicarboxylic acid used primarily as a pharmaceutical excipient, chemical intermediate, and food additive. It forms maleate salts with basic drugs, improving their aqueous solubility, stability, and oral bioavailability. Maleic acid is also used in the production of resins, agrochemicals, and polymers. It is generally recognized as safe for use in pharmaceutical and food applications at typical concentrations.

C4H4O4

116.07

116.01

110-16-7

Maleic Acid-d2;24461-33-4

444266

Monoclinic prisms from water
White crystals from water, alcohol and benzene
Colorless crystals

1.5±0.1 g/cm3

355.5±25.0 °C at 760 mmHg

134-138ºC

183.0±19.7 °C

0.0±1.7 mmHg at 25°C

1.526

-0.01

2

4

2

8

119

0

O([H])C(/C(/[H])=C(/[H])\C(=O)O[H])=O

VZCYOOQTPOCHFL-UPHRSURJSA-N

InChI=1S/C4H4O4/c5-3(6)1-2-4(7)8/h1-2H,(H,5,6)(H,7,8)/b2-1-

2-Butenedioic acid (2Z)-

Maleic acid Kyselina maleinova 2-Butenedioic acidcis-Butenedioic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~100 mg/mL (~861.55 mM)

Solubility in Formulation 1: 100 mg/mL (861.55 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)