Synthesis and Metabolism of Phenolic Compounds

This chapter concentrates on the synthesis and metabolism of phenolic compounds, and how the activities of these pathways and the compounds produced affect product quality. Phenolic compounds encompass a diverse group of molecules which include flavonoids, stilbenes, tannins, lignans, and lignin. Of the tens of thousands of phenolics found in plants, some are soluble in organic solvents, some are water soluble, and others are large insoluble polymers. Plant metabolism can be divided into primary pathways that are found in all cells and deal with the manipulation of a uniform group of basic compounds, and secondary pathways that occur in specialized cells and produce a wide variety of unique compounds. Precursors of phenylpropanoids are synthesized by two basic pathways: the shikimic acid pathway and the malonic pathway. The shikimic acid pathway produces most plant phenolics. The malonic pathway is an important source of phenolics in fungi and bacteria, but is less significant in higher plants.