title: An electron spin resonance study of free radicals from catechol estrogens.
abstract: Electron spin resonance spectroscopy has been used to demonstrate production of semiquinone free radicals from the oxidation of the catechol estrogens 2- and 4-hydroxyestradiol and 2,6- and 4,6-dihydroxyestradiol. Radicals were generated by horseradish peroxidase/H2O2 or tyrosinase/O2, or by autoxidation, and were detected as their complexes with spin-stabilizing metal ions (Zn2+ and/or Mg2+). Radical production occurs via one- or two-electron oxidation of catechol estrogens, depending on the type of activating system. Autoxidation of catechol estrogens produces superoxide and H2O2 at physiological pH values. The present results also indicate a difference in the reactivity of quinones derived from 2- and 4-hydroxyestradiol. The toxicological significance of these reactions is discussed.
mesh_terms: D000818:Animals; D016227:Benzoquinones; D055598:Chemical Phenomena; D002621:Chemistry; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism; D002393:Estrogens, Catechol / Q000378:metabolism*; D005260:Female; D005609:Free Radicals; D006735:Horseradish Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008954:Models, Biological; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D009195:Peroxidase; D010544:Peroxidases / Q000378:metabolism; D011809:Quinones / Q000378:metabolism / Q000633:toxicity; D014599:Uterus / Q000201:enzymology; D015032:Zinc / Q000494:pharmacology
chemical_list: D016227:Benzoquinones; D002393:Estrogens, Catechol; D005609:Free Radicals; D007527:Isoenzymes; D011809:Quinones; C025232:semiquinone radicals; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; C001390:2-hydroxyestradiol; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; D009195:Peroxidase; D014442:Monophenol Monooxygenase; D008274:Magnesium; D015032:Zinc; D010100:Oxygen