Studies on the interactions of bioactive quinone avarone and its methylamino derivatives with calf thymus DNA

The interactions of avarone, a quinone from the marine sponge Dysideaavara, and the methylamino derivatives of avarone (2), 3′-(methylamino)avarone (3) and 4′-(methylamino)avarone (4) with calf thymus DNA (CT-DNA) were studied. Agarose gel electrophoreticanalysis showed that binding of the quinones quenched fluorescence of ethidium bromide (EB). The extent of fluorescence quenching of intercalator EB by competitive displacement from EB–CT-DNA system and of groove binder Hoechst 33258 (H) from H–CT-DNA system with the quinones was analyzed by fluorescence spectroscopy. The obtained results demonstrated that the quinones reduced binding of both the intercalator EB and the minor groove binder H, indicating possible degradation of DNA. The substituent on the quinone moiety determined the extent of DNA damaging effect of the quinone, which was the most extensive with 3′-(methylamino)avarone and the least extensive with its regioisomer 4′-(methylamino)avarone. The results were confirmed by the observed hyperchromic effects in UV–visible spectra measured after interactions of the derivatives with CT-DNA.