Inhibition of 3,3QUOTATION_MARK,5,5QUOTATION_MARK-Tetramethylbenzidine and o-Phenylenediamine Peroxidation with 1-Amino-2-Naphtol-4-Sulfonic Acid and Its Polydisulfide

• Published in: Applied biochemistry and microbiology 2001-11, Vol.37 (6), p.610-617
• Main Authors: Karaseva, E I, Losev, YuP, Metelitsa, DI
• Format: Article
• Language: English
• ISSN: 0003-6838; 1608-3024
• DOI: 10.1023/A:1012311302920

The kinetics of coupled peroxidation of 3,3QUOTATION_MARK,5,5QUOTATION_MARK-tetramethylbenzidine (TMB) and 1-amino-2-naphtol-4-sulfonic acid (ANSA) or its polydisulfide (poly(ADSNSA)) was studied in a 0.01 M phosphate buffer (pH 6.4) at 20C. Both ANSA and poly(ADSNSA) strongly inhibited the TMB oxidation resulting in a marked delay in the product formation. Stoichiometric inhibition coefficients f, i. e., the average numbers of free-radical particles terminated by one inhibitor molecule, were estimated. The free-radical trapping effect of poly(ADSNSA) was 7.5 times greater than that of ANSA. Kinetics of coupled o-phenylenediamine (PhDA) and ANSA or poly(ADSNSA) oxidation was studied in phosphate-citrate buffers at pH 3 to 7. No lag periods in oxidation product accumulation were observed under any of the reaction conditions. A weak activation of PhDA conversion depending on pH and PhDA/ANSA ratios was observed at low ANSA concentrations, whereas increased ANSA or poly(ADSNSA) concentrations were inhibitory. The degree of PhDA-inhibition was maximal in acid media, reached minimum at pH 5 to 6, and than again increased at pH above 6. A tentative mechanism of coupled aromatic amine-phenol bi-substrate system peroxidation is discussed.