INTERACTION OF THE ANTITUMOR DRUG STREPTONIGRIN WITH PALLADIUM(II) IONS - EVIDENCE OF THE FORMATION OF A SUPEROXO-PALLADIUM(II)-STREPTONIGRIN COMPLEX

Streptonigrin, a potent antitumor agent of the quinone type, is able to form several types of complexes with Pd(II) ions. Using Potentiometric and spectroscopic measurements, we have shown that, at pH 7 in aqueous solution, [PdCl4]2− reacts with streptonigrin, forming a 1:1 Pd(II)-streptonigrin complex. This complex is able to catalyze the oxidation of NADH by dioxygen. Using EPR measurements, we have shown that NADH reduces the quinone group of the Pd(II)-streptonigrin complex to semiquinone. In the absence of dioxygen, the Pd(II)-streptonigrin (semiquinone) complex is very stable. The subsequent addition of dioxygen yields the formation of a superoxo-Pd(II)-streptonigrin complex, which, as time elapses, releases the initial Pd(II)-streptonigrin complex. © 1990, American Chemical Society. All rights reserved.