Acetaminophen, hydrogen peroxide determination

Various hydroxyl and amino derivatives of aromatic compounds are oxidized by peroxidases in the presence of hydrogen peroxide, yielding neutral or cation free radicals. Thus the phenacetin metabolites p-phenetidine (4-ethoxyaniline) and acetaminophen (TV-acetyl-p-aminophenol) were oxidized by LPO or HRP into the 4-ethoxyaniline cation radical and neutral V-acetyl-4-aminophenoxyl radical, respectively [198,199]. In both cases free radicals were detected by using fast-flow ESR spectroscopy. Catechols, Dopa methyl ester (dihydrox-yphenylalanine methyl ester), and 6-hydroxy-Dopa (trihydroxyphenylalanine) were oxidized by LPO mainly to o-semiquinone free radicals [200]. Another catechol derivative adrenaline (epinephrine) was oxidized into adrenochrome in the reaction catalyzed by HRP [201], This reaction can proceed in the absence of hydrogen peroxide and accompanied by oxygen consumption. It was proposed that the oxidation of adrenaline was mediated by superoxide. HRP and LPO catalyzed the oxidation of Trolox C (an analog of a-tocopherol) into phenoxyl radical [202]. The formation of phenoxyl radicals was monitored by ESR spectroscopy, and the rate constants for the reaction of Compounds II with Trolox C were determined (Table 22.1). 

Soc., 1999, 121, 3435 T. Hoshi, H. Saiki, S. Kuwazawa, Y. Kobayama and A. Anzai, Polyelectrolyte multilayer film-coated electrodes for amperometric determination of hydrogen peroxide in the presence of ascorbic acid, uric acid and acetaminophen, Anal. Sci., 2000, 16, 1009 E.S. Forzani, VM. Solis and E.J. Calvo, Electrochemical behavior of polyphenol oxidase immobilized in self-assembled structures layer by layer with cationic polyallylamine, Anal. Chem., 2000, 72, 5300 Y.M. Lvov, Z. Lu, J.B. Schenkman, X. Zu and J.F. Rusling, Direct electrochemistry of myoglobin and cytochrome P450cam in alternate layer-by-layer film with DNA and other polyions, J. Am. Chem. Soc., 1998, 120, 4073. 

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