Inhibition of Peroxidase-Catalyzed Oxidation of Aromatic Amines by Substituted Phenols

• Published in: Applied biochemistry and microbiology 2003-07, Vol.39 (4), p.352-362
• Main Authors: Metelitza, D I, Naumchik, I V, Karasyova, E I, Polozov, G I, Shadyro, O I
• Format: Article
• Language: English
• Subjects: Amines; Ethanol; Oxidation; Phenols
• ISSN: 0003-6838; 1608-3024
• DOI: 10.1023/A:1024508215662

Peroxidase-catalyzed oxidation of o-phenylene diamine (OPD) was competitively inhibited by trimethylhydroquinone (TMHQ), 4-tert-butylpyrocatechol (InH5), and 4,6-di-tert-butyl-3-sulfanyl-1,2-dihydroxybenzene (InH6). InH6 was the most efficient inhibitor (K^sub i^ = 11 μM at 20°C in 0.015 M phosphate-citrate buffer, pH 6.0). The effects of InH5 and InH6 were not preceded by periods of induction of OPD oxidation products (contrary to TMHQ). Peroxidase-catalyzed oxidation of tetramethylbenzidine (TMB) was noncompetitively inhibited by InH6 and 3-(2-hydroxyethylthio)-4,6-di-tert-butylpyrocatechol (InH4), whereas o-aminophenol acted as a mixed-type inhibitor. The effects of all three inhibitors were preceded by an induction period, during which TMB oxidation products were formed. Again, InH6 was the most efficient inhibitor (K^sub i^ = 16 μM at 20°C in 0.015 M phosphate-citrate buffer supplemented with 5% ethanol, pH 6.0). Judging by the characteristics of the inhibitors taken in aggregate, it is advisable to use the pairs OPD-InH5 and OPD-InH6 in systems for testing the total antioxidant activity of human biological fluids.[PUBLICATION ABSTRACT]