Topoisomerase I inhibitory and photocleavage activity by ruthenium complexes containing a new polyaza ligand

Two new ruthenium complexes containing a new polyaza ligand were found to inhibit the DNA supercoiled relaxation mediated by topoisomerase I (topo I), cleave DNA under irradiation and interact with CT-DNA by intercalation. Both complexes exhibited fast singlet oxygen generation rate, and DNA photocleavage reaction should be initiated by 1O2. Furthermore, complex 2 showed higher photocleavage activity, topo I inhibition activity, and DNA affinity than complex 1. This work shows that two complexes can act as DNA binders with high affinity and good DNA photocleavers. Furthermore, complex 2 can act as a good topo I inhibitor.