Biocatalytic oxidation of phenolic compounds by bovine methemoglobin in the presence of H2O2: Quantitative structure–activity relationships

[Display omitted] ► The kinetics of metHb-catalyzed oxidation of a group of phenols were analyzed. ► Unusual kinetic behaviour was observed for the phenols here tested. ► QSAR equations for a number of physicochemical parameters were established. ► A relationship between the peroxidase and catalase activities of metHb was found. ► Bovine metHb might represent a good economical alternative to other peroxidases. In the present work, 13 p-substituted phenols with different functional groups have been systematically evaluated as metHb substrates by means of HPLC analysis. Non-hyperbolic kinetics were observed and Hill coefficients in the 0.37–1.00 range were obtained. The catalytic constants and the Hill coefficients were found to be quantitatively correlated with two independent variables: the energy level of the highest-occupied molecular orbital (EHOMO), which describes the intrinsic redox activity of the substrates and the pKa-values, which are related to substrate ionization. Oxygen evolution in the presence of each phenol derivative was also measured, and good correlation between peroxidase-like and catalase-like activities of the protein was observed. It is also shown that bovine metHb, although less active than other peroxidases, may represent a good alternative from an economical point of view for phenol removal processes. The equations here obtained may serve as a basis to further explore the potential use of metHb-mediated reactions in the treatment of phenols in wastewaters and to predict which phenol will be removed most efficiently under this treatment with satisfactory reliability.