Natural biophenols are a wide group of molecules (over 8000 described so far) found only in the plant kingdom; their molecules display one or more aromatic rings carrying one or more hydroxyl groups; these molecules display remarkable antioxidant power and are produced as secondary metabolites by the plant for protection against the attack by bacteria, fungi, and insects (phytoalexins). Plant polyphenols include non-flavonoids or flavonoids; the latter are further divided into flavonols, flavononols, flavones, anthocyanins, procyanidins, phenolic acids, stilbenes, and tannins depending on the number of hydroxyls in the molecule and on the nature and the position of other substituents.