FIGURE 1.

Main groups of natural polyphenolic compounds (A–B). (A) Phenolic compounds (polyphenols) constitute one of the most numerous and widespread groups of plant substances. The structure of polyphenols can contain both simple molecules (phenolic acids) and highly polymerized compounds (condensed tannins). (B) It should be noted that the main share here falls on flavonoids. Structural changes in the rings subdivide flavonoids into several families: flavonols, flavones, flavanols, isoflavones, anthocyanins, etc. These families are often found in the form of glycosides. Various variations of flavonoids are linked by a common biosynthesis.