Synthesis, Topoisomerase I and II Inhibitory Activity, Cytotoxicity, and Structure-activity Relationship Study of Rigid Analogues of 2,4,6-Trisubstituted Pyridine Containing 5,6-Dihydrobenzo(h)quinoline Moiety

DNA topoisomerases are nuclear enzymes that transiently break one or two strands of DNA, passing a single or double stranded DNA through the break and again resealing the breaks which allow to solve various DNA topological problems ge-nerated during vital cellular proce sses such as replication, trans-cription, recombination, repair, chromatin assembly and chromo-some segregation.