Design and synthesis of Aza-boeravinone derivatives as potential novel topoisomerase I inhibitors

•Two types of novel 6H-chromeno[3,4-b]quinoline derivatives were designed and synthesized and evaluated for cytotoxic activity against six human tumor cell lines.•Compounds ZML-8 and ZML-14 exhibited effective inhibitory activities against HepG2 cell lines with IC50 values of 0.58 and 1.94 μM, respectively.•Compounds ZML-8 and ZML-14 exhibited selective toxicity against HepG2 and L-02 cells.•Compounds ZML-8 and ZML-14 merit further development for cancer treatment.