Evidence for hemin inducing the cleavage of peroxide bond of artemisinin (Qinghaosu): cyclic voltammetry and in situ FT IR spectroelectrochemical studies on the reduction mechanism of artemisinin in the presence of hemin

Cyclic voltammetry and in situ FT IR spectroelectrochemistry (SEC) were use d to monitor the change of the peroxide group of artemisinin in the presenc e of hemin. On the glassy carbon electrode, artemisinin alone was reduced a t potentials more negative than -1.0 V in CH2Cl2; no well-defined reduction peak was observed. In the presence of a concentration of hemin as low as 1 0(-7) M, artemisinin can be irreversibly reduced via hemin catalysis. In si tu FT IR SEC experiments confirmed the catalysis of hemin for the reduction of artemisinin. The changes of IR spectra for the peroxide bond of artemis inin at 1114 cm(-1) clearly showed hemin inducing the cathodic cleavage of the peroxide bond. These results might contribute to an understanding of th e antimalarial action of artemisinin. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.