Abstract
Peroxynitrite (ONOO-) is a reactive nitrogen species (RNS) that can be produced through the reaction between the reactive oxygen species (ROS) superoxide and the RNS nitric oxide (NO). ONOO- has been considered to be the most toxic RNS in mammalian systems because of its capability to nitrate tyrosine residue. Here we report that as similar to tyrosine, plant phenolic compounds also can be nitrated by an ONOO--independent mechanism. The phenolic compound p-coumaric acid (p-CA) was nitrated in the presence of horseradish peroxidase (HRP), NaNO2 and H2O2. The nitrating reaction was inhibited by KCN, an inhibitor for HRP. The antioxidant ascorbate suppressed p-CA nitration and its suppression time strongly depended on ascorbate concentration. The results suggest nitrogen dioxide radical is involved in the HRP-dependent p-CA nitration.
