METABOLISM OF THE ANTITUMOR DRUG N(2)-METHYL-9-HYDROXY ELLIPTICINIUM - IDENTIFICATION BY SURFACE-ENHANCED RAMAN-SPECTROSCOPY OF ADDUCTS FORMED WITH AMINO-ACIDS AND NUCLEIC-ACIDS

The bioxidative transformation of the antitumor drug N(2)-methyl-9-hyd roxy ellipticinium (NMHE) by the peroxidase-H2O2 system leads to a hig hly electrophilic quinoneimine species. This species may react with bi ological macromolecules such as proteins or nucleic acids, that contai n suitable nucleophilic groups, to give covalent adducts through a Mic hael addition at C(10). When this reaction takes place in the presence of aliphatic primary amines, recyclisation process occurs during coup ling leading to adducts of which the oxazolopyridocarbazole (OPC) stru cture has been established. Surface-enhanced Raman scattering (SERS) s pectra of these OPC were recorded and analyzed to serve as references. On the basis of these spectral data, the SERS investigation of adduct s obtained with aliphatic amino acids indicated that these species pre sent the same chromophoric OPC-type structure as those obtained with a liphatic amines. On the other hand, we have studied the covalent bindi ng of the drug to calf thymus DNA obtained under the same oxidative en zymatic procedure. Since previous studies have shown that adenosine wa s the preferential binding target within DNA, to determine the precise structure of DNA adducts we have synthesized a model adduct from this nucleoside to be used as a reference. Characterization by Fourier Tra nsform infrared spectroscopy (FTIR), Near-IR FT Raman, and SERS of thi s adenosine-NMHE adduct suggests that the covalent binding occurs betw een the C(10) of the ellipticinium chromophore and the N(6) primary am ine of the adenine. Finally, from hydrolysis of DNA adducts, their iso lation by high-performance liquid chromatography, and the analysis of the SERS spectrum of the main adduct formed, it appears that the struc ture is probably the same as that proposed for the adenosine-NMHE addu ct. (C) 1996 John Wiley & Sons, Inc.