Abstract
A series of novel 5-methoxy-2,3-naphthalimide derivatives were designed, synthesized and evaluated for their biological activities. In particular, the ability of the compounds to synergize with antimicrobials, to inhibit Nile Red efflux, and to target AcrB was assayed. The results showed that the most of the tested compounds more sensitized the Escherichia coli BW25113 to the antibiotics than the parent compounds 7 c and 15, which were able to inhibit Nile Red efflux. Significantly, compound A5 possessed the most potent antibacterial synergizing ac-tivity in combination with levofloxacin by 4 times and 16 times at the concentration of 8 and 16 mu g/mL, re-spectively, whilst A5 could effectively abolish Nile Red efflux at 100 mu M. Additionally, target effect of A5 was confirmed in the outer- or inner membrane permeabilization assays. Therefore, A5 is an excellent lead com-pound for further structural optimization.