Comparative study of aclacinomycin versus adriamycin by means of resonance Raman spectroscopy

Resonance Raman spectra of adriamycin and aclacinomycin A were examined in their H2O and D2O solutions. These spectra appear totally different from each other, but the differences are found to be similar to those between 1,4‐ and 1,8‐dihydroxyanthraquinone, which are considered to be model chromophores of adriamycin and aclacinomycin, respectively. Surface‐enhanced resonance Raman spectra of these two drugs were also compared by the use of silver sols. The effects of DNA binding on the resonance Raman spectra are also significantly different for these two drugs. Adriamycin was found to be intercalated in the CpG (or GpC) site of the DNA duplex, but aclacinomycin in the TpA (or ApT) site. Most of the differences in the spectra and sequence specificity are explained in terms of the molecular structures of their chromophores, i.e. in the adriamycin chromophore (1,4‐dihydroxyanthraquinone) two OH groups are hydrogen bonded to different CO groups, whereas in the aclacinomycin chromophore (1,8‐dihydroxyanthraquinone) two OH groups form hydrogen bonds with the same CO group, leaving the other CO group free from any intramolecular hydrogen bonding.