EPR DETECTION OF PHYTOPHENOXYL RADICALS STABILIZED BY ZINC IONS - EVIDENCE FOR THE REDOX COUPLING OF PLANT PHENOLICS WITH ASCORBATE IN THE H2O2-PEROXIDASE SYSTEM
H. Yamasaki et Sc. Grace, EPR DETECTION OF PHYTOPHENOXYL RADICALS STABILIZED BY ZINC IONS - EVIDENCE FOR THE REDOX COUPLING OF PLANT PHENOLICS WITH ASCORBATE IN THE H2O2-PEROXIDASE SYSTEM, FEBS letters, 422(3), 1998, pp. 377-380
Chlorogenic acid (CGA; 3-o-caffeoylquinic acid), a phenylpropanoid met
abolite of plants, was oxidized by H2O2 in the presence of horseradish
peroxidase. The primary and secondary oxidized products both were fre
e radicals which gave EPR multiline signals at g = 2.0044 and 2.0042 i
n the presence of zinc as a spin stabilizing agent. The EPR kinetics s
howed that ascorbate functioned as a cooperative reductant by regenera
ting CGA from its corresponding radicals. These results provide eviden
ce to support the idea that the ascorbate-phenolic redox couple in con
junction with guaiacol peroxidase is an efficient H2O2 scavenging mech
anism in higher plants. (C) 1998 Federation of European Biochemical So
cieties.