Spectroscopic studies on the anticancer antibiotic Altromycin H and the interaction with copper(II) ions.

The antitumor antibiotic Altromycin H was studied using electronic absorption (UV-Vis.) and circular dichroism (CD) spectroscopy. The dissociation constants of the phenolic groups on C(5) and C(11) were estimated as pK(1)=6.7 and pK(2)=11.8 at 25 degrees C, respectively, and a complete assignment of the CD and UV-Vis. bands is proposed. The interaction of Cu(II) ions with the Altromycin H has been also investigated by UV-Vis., CD and electron paramagnetic resonance (EPR) spectroscopy. A pH depended stepwise complex formation was observed. At pH<4 no copper-Altromycin H interactions were detected. At the 4