Nitration of phenol catalyzed by horseradish peroxidase

Horseradish peroxidase, an acidic peroxidase from the horseradish, is one of the most important enzymes as analytical reagent. The enzymatic nitration of phenol by oxidation of nitrite was studied using horseradish peroxidase in the presence of H₂O₂. The results showed that nitration occur at 2-and 4-positions of phenol. There were also minor products of hydroquinone and catechol. The influence of various reaction parameters, including pH, organic solvent, and concentration of H₂O₂, on nitration products were discussed. The best nitration pH was 7.0, and H₂O₂ should be added to the reaction mixture slowly.