(phenols) Compounds containing a benzene ring directly substituted with one or more hydroxyl groups. The simplest member is phenol (carbolic acid), formula C6
OH. Plant phenolics are widespread and extremely diverse and include the *flavonoids
. Simple phenolic compounds containing one or two rings are not as common as the flavonoids, though hydroquinone, coumarin, and the cinnamic acids are widely distributed. The amino acid tyrosine also contains a phenolic ring. Less common are such phenolics as catechol, phloroglucinol, and pyrogallol. Lignin is a phenolic, probably being formed from coniferyl alcohol, a derivative of cinnamic acid. Tannins are also derived from phenolics.