ABSTRACT
Plant phenolic compounds belong to a poorly defined group of products called secondary metabolites. Originally, secondary products were those regarded as either metabolic wastes or substances with no role in fundamental life processes; they were also thought to be unusual compounds limited in distribution among plants. The evolution of phenolic compounds may have been in response to the lack of motility in plants. These compounds may have offered protection from predators and from ultraviolet (UV) radiation, which was much more intense when higher plants were evolving. One of the products of phenolic biosynthesis is lignin, a cell-wall component of all vascular plants. Lignin precursors are formed in the endoplasmic reticulum, packaged into vesicles, and transported to the cell walls. Phenolic compounds are also involved in the growth status of plants. Phenolic compounds are involved in plant responses to environmental stresses including wounding, pathogen attack, mineral deficiencies, and temperature stress.
