A PEROXIDASE PHENOLICS/ASCORBATE SYSTEM CAN SCAVENGE HYDROGEN-PEROXIDE IN PLANT-CELLS/

The function of a peroxidase/phenolics/ascorbic acid system in plant v acuoles has not yet been well elucidated. We wished to study the redox reactions among hydrogen peroxide, phenolics and ascorbic acid (AA) i n the presence of horseradish peroxidase. Horseradish peroxidase oxidi zed rutin and chlorogenic acid (CGA), compounds present in many kinds of plant. The oxidation was inhibited by AA. As a result of the inhibi tion, AA was oxidized and when almost all of it had been oxidized, oxi dation of the phenolics commenced. Monodehydroascorbic acid (MDA) radi cal was detected during the oxidation of AA, suggesting that the inhib ition of oxidation of rutin and CGA was due to reduction of phenoxyl r adicals by AA. By comparison of time courses of changes in levels of A A and MDA radicals, and by kinetic calculation, it is suggested that i n addition to AA, MDA radicals may also reduce phenoxyl radicals. It i s proposed that the peroxidase/phenolics/AA system can function as a h ydrogen peroxide scavenging system.