Synthesis and in vitro cytotoxic effect of 6-amino-substituted 11H- and 11Me-indolo[3,2-c]quinolines

• 11N–H and 11N–Me indolo[3,2-c]quinolines were tested.
• The 3-aminopropylamino groups at C6 enhanced cytotoxicity.
• High cytotoxicity was achieved with 11N–Me derivatives.
• The nitro group at C2 best contributed to cytotoxicity.
• 11N–Me group slightly enhances the DNA intercalating constant.

A series of 6-amino-11H- indolo[3,2-c]quinoline derivatives with various substituents on the quinoline ring were synthesized. A methyl group introduced to N-11 of the intermediate 4 to elaborate novel analog 7. The cytotoxic effect of these 6-amino-substituted 11H- and 11-methyl-indolo[3,2-c]quinoline derivatives in vitro were tested against MV4-11 (human leukemia), A549 (non-small cell lung cancer) and HCT116 (colon cancer) and BALB/3T3 (normal murine fibroblasts). All the N-11 methylated compounds significantly increased the cytotoxicity. Compound 7p was most active with the IC50 value of 0.052 μM against the MV4-11 cell line, and also exhibited a selective activity against A549, HCT116 and BALB/3T3 cell line, with the respective IC50 values of 0.112, 0.007 and 0.083 μM, which were higher or comparable to those of the anticancer drug doxorubicin HCl. The binding constants of 5g and 7h to salmon fish sperm DNA were also evaluated using UV–vis absorption spectroscopy, indicating intercalation binding with constants of 1.05 × 106 L/mol and 4.84 × 106 L/mol.

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