The present study aimed to investigate, for the first time, the rate of the oxidation reaction of some derivatives of phenol and aromatic amines, that is, pyrogallol, catechol, resorcinol, ortho-aminophenol, meta-aminophenol, para-aminophenol, ortho-phenylenediamine, and para-phenylenediamine, in the presence of hydrogen peroxide in pure and magnetized solvents using horseradish peroxidase enzyme. The reaction was studied in the absence and presence of a magnetized solvent under completely identical conditions. The results showed that magnetized solvent could change the structure of the enzyme and reduce its activity. In addition, it affected the rate of oxidation of the selected derivatives through altering the strength of the hydrogen bonds of the system. The changes in the structure and activity of the enzyme were examined using UV-Vis and fluorescence spectroscopy as well as viscosity measurement technique. Examination of the secondary structure via the far UV-CD spectrum indicated the increase in the alpha helical structure in the magnetized solvent. When dissolved in a magnetized solvent, hydrogen peroxide as an enzyme substrate reduced the rate of enzymatic reaction and provided lower saturation conditions for the enzyme compared with when it was dissolved in the pure solvent.