Aloe-emodin derived azoles as a new structural type of potential antibacterial agents: design, synthesis, and evaluation of the action on membrane, DNA, and MRSA DNA isomerase‡

As serious global drug resistance motivated the exploration of new structural drugs, we developed a type of novel structural aloe-emodin azoles as potential antibacterial agents in this work. Some target aloe-emodin azoles displayed effective activity against the tested strains, especially tetrazolyl aloe-emodin 4b showed a low MIC value of 2 μg mL−1 towards MRSA, being more efficient than the reference drug norfloxacin (MIC = 8 μg mL−1). Also, the active molecule 4b exhibited low cytotoxicity against LO2 cells with no distinct tendency to induce the concerned resistance towards MRSA. The tetrazolyl derivative 4b was preliminarily investigated for the possible mechanism; it was revealed that tetrazolyl derivative 4b could both disrupt the integrity of MRSA membrane and form 4b–DNA supramolecular complex by intercalating into DNA. Moreover, tetrazolyl aloe-emodin 4b could bind with MRSA DNA isomerase at multiple sites through hydrogen bonds in molecular simulation.