Phenolic compounds
Phenolic compounds are secondary metabolites that are responsible for sensory properties of foods, like taste, color, aroma and texture.

 

 

Chemically, they are a very diverse group of compounds with at least one aromatic ring and one –OH group bound to this aromatic ring. They are called phenolics or polyphenols, too. Many different ways of classifying the phenolics can be found in the literature. The classification that is becoming generally more accepted and more recognized is based on the number of C-atoms in their basic skeleton. One of the many classifications found in literature divides them in simple phenols and polyphenols, possessing at least two phenol subunits, including stilbenes and flavonoids and those compounds having three or more phenol subunits (tannins). So far more than 20.000 compounds have been identified with flavonoids (more than 8.000) as the most numerous among them. They are mainly found in fruits and vegetables, and in micro-organisms, but not in animal organisms. The richest sources of phenolics are green and black tea, red wine, coffee, cocoa and chocolate. Fruits and vegetables in general have much lower levels of phenolics, although along with herbs, spices, nuts, olive oil and algae, they are potentially significant sources of these phytochemicals. A database giving the contents of different phenolics in various foods has been set up by INRA, Clermont-Ferrand, France, and is available on the webpage (http://www.phenol-explorer.eu).

In vitro, phenolic compounds have been shown to have many biological effects. Food industry is interested in them particularly because they are good antioxidants and can therefore prevent oxidation processes and prolong the stability of foods, and because they can act as antimicrobials. In human diet, phenolics are believed to provide health benefits that have been associated with a reduced risk of chronic diseases, acting as antioxidants.  Antioxidants have the ability to reduce free radicals by donating hydrogen atom or electrons, and to quench singlet oxygen and bind metal ions in complexes.

The researchers are aware that a fate of phenolic compounds in human body is very important when confirming and explaining their in vivo effects. Practically, it is very difficult to investigate cellular and tissue uptake in humans and the data on tissue distribution come from animal studies mainly.

The text was prepared by Veronika Abram, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.

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