*3.1.3. Synthesis by plants*

There is a vast distribution of phenolic compounds in the plant kingdom. Synthesis of phe‐ nolic compounds in plants occurs in the chlorophyll under the influence of certain external stimuli or factors including ultraviolet radiation from sunlight, chemical stressors (cations, pesticides), and microbial infections. Phenylalanine is a precursor for phenolic compound synthesis in plants. Typically, phenylalanine is deaminated to cinnamate through phenylala‐ nine ammonia‐lysase catalysis. A hydroxylation process catalysed by cinnamate‐4‐hydroxy‐ lase then results in the conversion of cinnamate to coumaric acid which becomes the starting material for the synthesis of stilbenes, flavonoids and furanocoumarines including other classes of phenolics catalysed by different enzymes [20]. These compounds are stored in the leaves, roots and stems of plants. Roots and leave exudates of plants contain these phenolic compounds, which are finally introduced into the soil by the exudates. Decomposition of dead leaves, roots and plants also introduces the phenolic compounds into the soil. Runoff from land then washes these compounds into the nearby water bodies.
