**5. Phenolic compounds**

Phenolics are organic compounds containing one aromatic ring to which is attached one or more hydroxyl groups [11]. Phenolic compounds represent one of the most extensive groups of plants' secondary metabolites [20]. They are contained in a great share in the daily diet due to their countless benefits for human health and well- being. Henceforth, the consumption of phenolic-rich fruits and vegetables, such as berries and spinach, is increasingly recommended [20].

They are synthesized either through the shikimic acid or the acetic acid pathways. Phenylpropanoids are the result compounds of the shikimic acid pathway while simple phenols result from the acetic acid pathway acid. However, both pathways result in the formation of flavonoids, abundant phenolic compounds [21].

In addition to the presence of aromatic rings and hydroxyl substitutions, phenolic compounds are less likely to be found in the free form, rather, they are most frequently bound to other complex compounds as sugars to reduce their toxicity [21].
