title: 2,3-Dimethoxybenzo[i]phenanthridines: topoisomerase I-targeting anticancer agents.
abstract: Appropriately substituted benzo[i]phenanthridines structurally related to nitidine, a benzo[c]phenanthridine alkaloid with antitumor activity, are active as topoisomerase I-targeting agents. Studies on benzo[i]phenanthridines have indicated analogues that possess a 2,3-methylenedioxy moiety and at least one and preferably two methoxyl groups at the 8- and 9-positions, such as 8,9-dimethoxy-2,3-methylenedioxybenzo[i]phenanthridine, 2, are active as topoisomerase I-targeting agents. Tetramethoxylated benzo[i]phenanthridines, wherein the 2,3-methylenedioxy moiety is replaced with methoxyl groups at the 2- and 3-position, are inactive as a topoisomerase I-targeting agent. These results initially suggested that the 2,3-methylenedioxy moiety was critical to the retention of potent activity. Further studies revealed that 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine, 7a, is more potent than 2 as a topoisomerase I-targeting agent. The observation that 2,3-dimethoxylated benzo[i]phenanthridines can actually exhibit enhanced activity prompted the present study in which several 8-substituted 2,3-dimethoxybenzo[i]phenanthridines were prepared and their pharmacological activities evaluated. The influence of NH(2), CN, CH(2)OH, OBn, OCH(3), OH, and NHCOCH(3 )substituents at the 8-position on the relative activity of these 2,3-dimethoxybenzo[i]phenanthridines was examined. Relative to these derivatives, 7a was the most potent topoisomerase I-targeting agent, possessing similar cytotoxicity to that of nitidine in the human lymphoblast tumor cell line, RPMI8402.
authors.affiliation: Department of Pharmaceutical Chemistry, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, NJ 08854-8020, Piscataway, USA.
authors.forename: Dajie
authors.initials: D
authors.lastname: Li
authors.forename: Baoping
authors.initials: B
authors.lastname: Zhao
authors.forename: Sai Peng
authors.initials: SP
authors.lastname: Sim
authors.forename: Tsai Kun
authors.initials: TK
authors.lastname: Li
authors.forename: Angela
authors.initials: A
authors.lastname: Liu
authors.forename: Leroy F
authors.initials: LF
authors.lastname: Liu
authors.forename: Edmond J
authors.initials: EJ
authors.lastname: LaVoie
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology*; D006801:Humans; D007202:Indicators and Reagents; D010617:Phenanthridines / Q000138:chemical synthesis* / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013778:Tetrazolium Salts; D013844:Thiazoles; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D010617:Phenanthridines; D013778:Tetrazolium Salts; D013844:Thiazoles; D059004:Topoisomerase I Inhibitors; D004247:DNA; C022616:thiazolyl blue; D002166:Camptothecin