EPR detection of phytophenoxyl radicals stabilized by zinc ions: evidence for the redox coupling of plant phenolics with ascorbate in the H2O2-peroxidase system.
Chlorogenic acid (CGA; 3-o-caffeoylquinic acid), a phenylpropanoid metabolite of plants, was oxidized by H2O2 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 H2O2 scavenging mechanism in higher plants.
Yamasaki
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Photobioenergetics Group, Research School of Biological Sciences, The Australian National University, Canberra, ACT. yamasaki@sci.u-ryukyu.ac.jp
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D001205:Ascorbic Acid / Q000378:metabolism; D002726:Chlorogenic Acid / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000378:metabolism; D005609:Free Radicals / Q000032:analysis / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis* / Q000737:chemistry; D010944:Plants / Q000378:metabolism; D015032:Zinc / Q000737:chemistry
D016166:Free Radical Scavengers; D005609:Free Radicals; D010636:Phenols; D002726:Chlorogenic Acid; C042329:phenoxy radical; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D015032:Zinc; D001205:Ascorbic Acid