ABSTRACT
The different classes of phenolics serve a variety of functions within plants, from poisons to antibacterial compounds and plant pigments and scents. Plant phenolics serve a range of biological functions. They can provide visual signals, scents, and flavors that attract pollinators and deter herbivores. The flavors produced by the phenolics range from the pleasant-tasting vanillins, through to the pungent or astringent flavors of ginger (gingerols), capsicum peppers (capsaicin), and the tannins. Many of the phenolic compounds are important in protecting plants against bacterial and fungal pathogens. This chapter describes the biological functions and biochemical pathways leading to the synthesis of the four most abundant plant phenolic groups: simple phenolics, flavonoids, lignin, and tannins. Almost all plant phenolic compounds are synthesized from phenylpropanoid precursors. Hydrolyzable tannins are polymers of carbohydrates and the simple phenolics, gallic and ellagic acids. The early steps in monolignol biosynthesis are the core reactions of the phenylpropanoid pathway.
