Methyl anthranilate

Description

Methyl anthranilate, also known as MA, is a benzoate ester that is the methyl ester of anthranilic acid. It has a role as a metabolite and a flavouring agent.  Methyl anthranilate has been reported in Camellia sinensis, Citrus reticulata, and other organisms with data available. It is an essential aroma chemical for orange flower notes, as well as jasmine and tuberose. It has a distinctly grape-like odour which makes it great for fruit bases also. 

Chemical properties

Methyl Anthranilate occurs in a large number of blossom essential oils (e.g., neroli, ylang-ylang, and jasmine oils), grapes, and citrus oils. It occurs as white crystals (mp 24–25°C), or a yellowish liquid, that show blue fluorescence and have an orange blossom odor. Methyl anthranilate is prepared by esterification of anthranilic acid with methanol or by reaction of isatoic anhydride with methanol.
It is used in a large number of blossom fragrances. However, its use in perfumes for soaps and cosmetics is limited because it causes discoloration. It is used in flavor compositions (e.g., in grape and citrus flavors).

Occurrence

Methyl anthranilate naturally occurs in the Concord grapes and other Vitis labrusca grapes or hybrids thereof, and in bergamot, black locust, champaca , gardenia, jasmine, lemon, mandarin, neroli, oranges, rue oil, strawberry, tuberose, wisteria, galangal and ylang ylang. It is also a primary component of the essential apple flavor, along with ethyl acetate and ethyl butyrate.It is also secreted by the musk glands of foxes and dogs, and lends a "sickly sweetness" to the smell of rotting flesh.

The Uses of Methyl anthranilate

Methyl anthranilate acts as a bird repellent. It is food-grade and can be used to protect corn, sunflowers, rice, fruit, and golf courses. Dimethyl anthranilate (DMA) has a similar effect. It is also used for the flavor of grape Kool Aid. It is used for flavoring of candy, soft drinks (e.g. grape soda), gums, and drugs.
Methyl anthranilate both as a component of various natural essential oils and as a synthesised aroma-chemical is used extensively in modern perfumery . It is also used to produce Schiff's Bases with aldehydes, many of which are also used in perfumery. In a perfumery context the most common Schiff's Base is known as aurantiol - produced by combining methyl anthranilate and hydroxyl citronellal.

Definition

ChEBI: Methyl anthranilate is a benzoate ester that is the methyl ester of anthranilic acid. It has a role as a metabolite and a flavouring agent. It derives from an anthranilic acid.

Preparation

By heating anthranilic acid and methyl alcohol in the presence of sulfuric acid and subsequent distillation.

Synthesis Reference(s)

Tetrahedron Letters, 33, p. 3599, 1992 DOI: 10.1016/S0040-4039(00)92512-7

Air & Water Reactions

Methyl anthranilate is sensitive to air and light. Slightly water soluble .

Reactivity Profile

An amine and ester. Amines are chemical bases. They neutralize acids to form salts plus water. These acid-base reactions are exothermic. The amount of heat that is evolved per mole of amine in a neutralization is largely independent of the strength of the amine as a base. Amines may be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen is generated by amines in combination with strong reducing agents, such as hydrides. Esters react with acids to liberate heat along with alcohols and acids. Strong oxidizing acids may cause a vigorous reaction that is sufficiently exothermic to ignite the reaction products. Heat is also generated by the interaction of esters with caustic solutions. Flammable hydrogen is generated by mixing esters with alkali metals and hydrides.

Fire Hazard

Methyl anthranilate is combustible.

Safety Profile

Moderately toxic by ingestion. Experimental reproductive effects. A skin irritant. See also ESTERS. Combustible liquid. When heated to decomposition it emits toxic fumes of NOx.

Toxicology

Methyl anthranilate is a colorless liquid that has a sweet, fruity, grape-like flavor. It is found in the essential oils of orange, lemon, and jasmine and has been widely used to create imitation Concord grape flavor. Table 10.8 shows the acute toxicity of methyl anthranilate. Methyl anthranilate promotes some allergic reactions on human skin, which has led to it being prohibited for use in cosmetic products.

Safety

Methyl anthranilate is a plant-based compound with a long history of use as a flavor additive for foods and  beverages, and as an aromatic used extensively in perfumery. As such,  the US Department of Agriculture (USDA) and the Food and Drug  Administration (FDA) have approved MA as "generally recognized as safe".

Metabolism

It is probable that this ester is hydrolysed and the anthranilate is excreted mostly as oaminobenzoyl glucuronide (Charconnet-Harding, Dalgliesh & Neuberger, 1953).

Solubility in organics

Methyl anthranilate is soluble in ethanol and propylene glycol. It is insoluble in paraffin oil.

Toxicity evaluation

Even though MA is palatable to humans, it is an irritant to birds. The bird-repellent properties of MA and related compounds were discovered in the late 1950s (25). The mode of action is via the trigeminal nerve. Thus, all avian species tested so far perceive MA as an irritant, not as a taste repellent per se.