Abstract SecA, a key component of bacterial Sec-dependent secretion pathway, is an attractive target for exploring novel antimicrobials. Rose bengal (RB), a polyhalogenated fluorescein derivative, was found from our previous study as a potent SecA inhibitor. Here we describe the synthesis and structure–activity relationships (SAR) of 23 RB analogues that were designed by systematical dissection of RB. Evaluation of these analogues ...