*2.5.2 Biosynthesis of phenolic acids*

Phenolic acids are not abundant in most plants. There are in the form of gallic acid and salicylic acid. Gallic acid may be a precursor for the ellagitannins and gallotannins. Salicylic acid is an important defense property that mediates systemic acquired resistance (SAR), and it is also used as a signaling molecule to relay information on pathogen attack to other parts of the plant. After receiving the SA signal, a defense response is trigger the biosynthesis of pathogenesis-related (PR) proteins [8, 10].
