The ability of two platinum(IV) antitumor agents, cis,cis,trans-PtIV[(CH3)2CHNH2]2Cl2(OH)2 (2) and cis,-cis,tranS-PtIV(NH3)2Cl2OH)2 (4), to interact with PM2 DNA was examined. Analysis using gel electrophoresis showed that neither compound is able to alter the electrophoretic mobihties of the three forms of PM2 DNA in the gel. However, incubation of 2 and 4 with 2 equiv of Fe(ClO4)2·6H2O or 1 equiv of ascorbic acid results in reduction to yield the divalent complexes m-PtII(NH3)2Cl2 (1) and cis-PtII-[(CH3)2CHNH2]2C12 (3). The structures of the reduction products were characterized by using elemental analysis as well as infrared and 195Pt NMR spectroscopies. Both 1 and 3 were found to bind to and unwind supercoiled form I PM2 DNA. The aforementioned observations support the suggestion that reduction is a means of activating the antitumor properties of 2 and 4.
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