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EPR detection of phytophenoxyl radicals stabilized by zinc ions: evidence for the redox coupling of plant phenolics with ascorbate in the H 2 O 2 ‐peroxidase system
Author(s) -
Yamasaki Hideo,
Grace Stephen C
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00048-9
Subject(s) - chemistry , electron paramagnetic resonance , radical , peroxidase , ascorbic acid , horseradish peroxidase , redox , guaiacol , zinc , chlorogenic acid , nuclear chemistry , inorganic chemistry , organic chemistry , chromatography , enzyme , food science , physics , nuclear magnetic resonance
Chlorogenic acid (CGA; 3‐ o ‐caffeoylquinic acid), a phenylpropanoid metabolite of plants, was oxidized by H 2 O 2 in the presence of horseradish peroxidase. The primary and secondary oxidized products both were free radicals which gave EPR multiline signals at g =2.0044 and 2.0042 in the presence of zinc as a spin stabilizing agent. The EPR kinetics showed that ascorbate functioned as a cooperative reductant by regenerating CGA from its corresponding radicals. These results provide evidence to support the idea that the ascorbate‐phenolic redox couple in conjunction with guaiacol peroxidase is an efficient H 2 O 2 scavenging mechanism in higher plants.