INFLUENCE OF QUINOLINE-CONTAINING ANTIMALARIALS IN THE CATALASE ACTIVITY OF FERRIPROTOPORPHYRIN-IX

A kinetic study of the catalytic activity of ferriprotoporphyrin IX in the decomposition of the hydrogen peroxide was carried oat at (30.0 /- 0.1)degrees C, in 0.10 M NaCl, in the absence and irt the presence of quinoline-containing antimalarials, i.e., chloroquine, quinine, qui nidine, and quinacrine. An inhibitory effect on the catalase activity was observed, for all the studied drugs, at concentrations Icp to 20 m u M. For chloroquine the determined rate constants, in the range of [c atalyst] from 0.5 to 16 mu M, were k(obs) = (2.23 +/- 0.06) X 10(-2) s (-1) and (6.23 +/- 0.15) X 10(-1) s(-1), respectively, in the absence and in the presence of the drug. Catalase activity was accompanied by pel oxidase activity, as verified try degradative oxidation of the hem e itself. Chloroquine inhibited both the catalyse and the peroxidase a ctivities of hemin, the latter against the catalyst itself. The effect on the catalase activity, however is more pronounced. Based on the ob tained results, a mechanism is proposed to explain the effect of antim alarials on the reactivity of the ferriprotoporphyrin IX, suggesting t hat the interaction of the drug with the heme ring plays a fundamental role. (C) 1997 Elsevier Science Inc.