Synthesis, biological activity and comparative analysis of DNA binding affinities and human DNA topoisomerase I inhibitory activities of novel 12-alkoxy-benzo[c]phenanthridinium salts

New antitumor 12-alkoxy-benzo[c]phenanthridinium derivatives were obtained in high yields through multistep syntheses. Analysis of DNA binding and human DNA topoisomerase I inhibitory activities demonstrates that new compounds, combining 2, 6, and 12 substitutions, interact strongly with DNA and exhibit important topoisomerase I inhibition. The cytotoxicities against solid tumor cell lines are also determined and compared with those for fagaronine and ethoxidine