Synthesis and structure-activity relationships of novel neocryptolepine derivatives

Herein we reported the synthesis of a novel series of neocryptolepine(5-methyl-5H-indolo[2,3-b]quinoline) derivatives containing different substituents at C11 using methyl 1H-indole-3-carboxylate and N-methylaniline as starting material. The target 21 compounds were evaluated for their antibacterial activity in vitro against gram-positive bacteria(B. subtilis and S. aureus) and gram-negative bacteria(E.coli and S. typhi). Almost all the tested compounds showed moderate to high activities against the four bacterial strains at the minimum inhibitory concentrations(MICs) of 1—10 μg/mL. The obtained results suggest that part of the novel synthetic neocryptolepine derivatives exhibit significant antibacterial effect against all the tested organisms.