title: Formation of methemoglobin and phenoxyl radicals from p-hydroxyanisole and oxyhemoglobin.
abstract: The reaction of p-hydroxyanisole with oxyhemoglobin was investigated using electron spin resonance spectroscopy (ESR) and visible spectroscopy. As a reactive reaction intermediate we found the p-methoxyphenoxyl radical, the one-electron oxidation product of p-hydroxyanisole. Detection of this species required the rapid flow device elucidating the instability of this radical intermediate. The second reaction product formed is methemoglobin. Catalase or SOD had no effect upon the reaction kinetics. Accordingly, reactive oxygen species such as hydroxyl radicals or superoxide could not be observed although the spin trapping agent DMPO was used to make these short-lived species detectable. When the sulfhydryl blocking agents N-ethylmaleimide or mersalyl acid were used, an increase of the methemoglobin formation rate and of the phenoxyl radical concentration were observed. We have interpreted this observation in terms of a side reaction of free radical intermediates with thiol groups.
authors.affiliation: Institute of Pharmacology and Toxicology, Vet. Med. University of Vienna.
authors.forename: K
authors.initials: K
authors.lastname: Stolze
authors.forename: H
authors.initials: H
authors.lastname: Nohl
mesh_terms: D000840:Anisoles / Q000009:adverse effects / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D066298:In Vitro Techniques; D008706:Methemoglobin / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism; D010636:Phenols / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D000840:Anisoles; D000970:Antineoplastic Agents; D005609:Free Radicals; D010108:Oxyhemoglobins; D010636:Phenols; C042329:phenoxy radical; C009760:mequinol; D008706:Methemoglobin