Ruthenium (II) complexes containing a new asymmetric ligand: DNA interaction, photocleavage and topoisomerase I inhibition

A new asymmetric ligand 2-(pyridine-2-yl)-1-H-imidazo[4,5-g]acenaphtho[1′,2′:2,3]quinoxaline (piaq) and its ruthenium complexes with [Ru(L)2(piaq)]2+ (L = bpy (2,2′-bipyridine), phen (1,10-phenanthroline)), have been synthesized, and their DNA-binding, photocleavage and DNA topoisomerase I inhibition properties were measured. Results suggested that both Ru(II) complexes can intercalate into DNA base pairs. Furthermore, the two complexes are efficient DNA-photocleavers under irradiation at 365 nm, and singlet oxygen (1O2) is the active specie in DNA photocleavage. Topoisomerase inhibition and DNA strand passage assay suggested that both complexes are efficient inhibitors of DNA topoisomerase I.