Aromatic amino acids are organic compounds that contain a carboxyl group, a benzene ring, an amino group. The presence of several functional groups explains the dual properties of these organic substances.
Being in nature
Aromatic amino acids are part of the tissues and cells of living organisms. Despite the diversity of representatives of this class, only 20 amino acids are monomers for building proteins and peptides. Benzoic acid, such as found in cranberries, has excellent antioxidant properties.
Many microorganisms and plants are able to independently synthesize some of the aromatic amino acids necessary for full functioning.
They take an active part in carbohydrate and protein metabolism, are part of nucleic acids,vitamins, hormones, pigments, alkaloids, antibiotics, toxins. Some mediate the transmission of nerve impulses.
Classification
There is a division of representatives of this class of organic oxygen-containing compounds according to structural features.
Taking into account the location of the amino and carboxyl functional groups, they are isolated
α-, β-, γ-, δ-, ε- acids.
According to the number of groups, basic, neutral, acidic substances are distinguished.
Depending on the structure of the hydrocarbon radical, aromatic amino acids, aliphatic, heterocyclic, sulfur-containing substances are isolated.
Important information
To name these organic compounds, systematic nomenclature is used. Aromatic amino acids are derivatives of benzene, in the side chain of which one or more carboxyl (acid) groups appear. The simplest representative of this class is benzoic acid. The introduction of a hydroxyl group into the side chain leads to the formation of salicylic acid.
Derivatives of aromatic amino acids - esters and amides - are used in the chemical industry.
Historical note on benzoic acid
Benzoic acid has been known to mankind since ancient times. In the sixteenth century, it was isolated by sublimation from resin. In the 19th century, German chemists studied the chemical properties of this compound, compared it with hippuricacid. Due to its antifungal and antimicrobial effects, benzoic acid has been used as a food preservative in the food manufacturing process. It is indicated on product labels as additive E 210.
Physical and chemical properties
In appearance, benzoic acid is similar to oblong thin white needles with a specific luster. It is highly soluble in various media: alcohols, fats, water. The melting point of this aromatic amino acid is 122 degrees Celsius. It goes from solid to gas.
In large volumes, benzoic acid is produced by the oxidation of toluene (methylbenzene).
It is a natural compound, as it is found in some berries: lingonberries, blueberries, cranberries. In addition, benzoic acid is formed in such fermented milk products as yogurt, curdled milk. The compound is non-toxic, not dangerous to humans if consumed in small amounts.
Chemical properties
Qualitative reaction for aromatic amino acids - electrophilic substitution in the aromatic ring (nitration with concentrated nitric acid). The xantoprotein reaction is used to detect the following aromatic acids: tyrosine, phenylalanine, tryptophan, histidine. The process is accompanied by the formation of a bright yellow product.
Another qualitative reaction for aromatic amino acids is ninhydrin, which is used when conductingquantitative and qualitative determination of not only amino acids, but also amines. When ninhydrin is heated in an alkaline solution with compounds in which primary amino groups are present, a blue-violet product is obtained.
This chemical reaction is also used to identify secondary amino groups in aromatic acids: hydroxyproline and proline. Their presence can be judged by the formation of a stable bright yellow product. When conducting modern chemical analysis of aromatic amino acids, it is the ninhydrin reaction that is used.
Paper chromatography method makes it possible to detect each amino acid in the taken mixture in an amount of two to five micrograms.
Application
Food preservative E 210 (benzoic acid) is used in the confectionery, brewing, and baking industries. Here is a list of products whose production is inextricably linked with the use of benzoic acid: ice cream, canned vegetables, beer, liqueurs, sugar substitutes, pickled and s alted fish, chewing gum, butter, margarine.
Not without this aromatic acid and the manufacture of some cosmetics. Often it is added to medicines, for example, to antiseptic ointments. Pharmacists are turning to benzoic acid for its preservative properties.
This organic compound copes well with a variety of fungi, microbes, and simple parasites. That is why benzoic acidadded to children's cough syrups. It has an expectorant effect, softens sputum, removes it from the bronchi. Highly effective medical solutions intended for foot baths, which contain benzoic acid.
Organic compound helps to eliminate excessive sweating of the feet. Benzoic acid is considered an effective remedy for fighting fungal skin lesions. In the chemical industry, benzoic acid is used as the main reagent in the manufacture of many organic compounds.
When it enters the human body, benzoic acid enters into chemical interaction with protein molecules.
It is transformed into hippuric acid, then it is excreted in the urine from the body.
