THE DIRECT REDUCTION OF CYTOCHROME-C BY SOME ANTHRAQUINONE ANTITUMOR COMPOUNDS

The ability of various anthraquinone antitumor agents to undergo oxida tive metabolism with concomitant cytochrome c reduction has been exami ned. The reduction of cytochrome c by the compounds had enzymatic char acter and occurred without the formation of oxygen radicals. We have f ound that the presence of at least two phenolic groups in ring A of th e compounds studied was indispensable for their oxidative metabolism. It is suggested that these groups are essential for the binding to cyt ochrome c. Furthermore, it has been shown that the existence of hydrox y groups in side chains of these compounds augments their interaction with this hemoprotein. On the basis of the results obtained for a seri es of analogs of mitoxantrone. we can conclude that the structural fac tor directly responsible fur cytochrome c reduction is the primary or secondary amino group of the side chains.