Phenolic acids are a large group of phenolic compounds, which are found in foods of plant origin. Phenolic acids have different functions in plants including nutrient assimilation, protein synthesis, enzyme activity and photosynthesis. Share on derivatives cimetne and hydroxybenzoic acid. Most abundant hydroxy benzoic acid derivatives are phydroxybenzoates, vanilla, gallic, protokatehin and ellagic acid.
Protokatehinska acid is present in plants of different families, and gallic acid is a component of many substances taninskih (galotanini). For the aromatic nucleus can bind and methoxy groups, as is the case with vanilla acids.
The molecules of gallic acid can build a new CC link, which produces heksahidroksidifenska acid arises from the elimination of ellagic acid.
Phenolic acidsare known antioxidants because of the ability to turn hydrogen or an electron and because their stable radicals interemedijeri prevent oxidation of the various components, particularly fatty acids and oils.
Hydroxy derivatives of benzoic acid and cimetne are present in foods of plant origin (fruits, vegetables, cereals). They are found in all parts of plants (roots, stems, leaves, seeds). In different parts of plants are different concentrations of phenolic acids. In addition, in various stages of development are present in different plant phenolic acids. Growth conditions, such as temperature, affect the content of phenolic acids.
A small part of the phenolic acids in free form while most related ester, ether or acetal bond with structural components of plants (cellulose, lignin and protein) or with small organic molecules (glucose, kvinska, maleic and tartaric acid) and other natural products ( terpenes).
Hydroxybenzoic acids in free form and esterifikovanoj proven only in some higher plants. Cimetne acid (p-kumarna, tea, and ferulna sinapinska acid) are represented in more than hidroksibenzovu acid. Tea and acid forming kininska hlorogensku acid which is found in many fruits, and higher concentrations of coffee (one cup contains 70-350 mg hlorogenske acid). Cimetna acid is found in all parts of the fruit, and the highest content was found in the outer layer of ripe fruit. Brown acid is isolated from coffee. In a free and esterified form is the most zastupljna phenolic acids and is 75 to 100% of the total content of acid derivatives cimetne in fruit. The most important source of acid ferulne the grains in which the dominant phenolic acids.