Natural and nature-inspired compounds targeting E. coli WrbA as antibiofilm agents: computational studies, synthesis, and biological evaluation

Antimicrobial Resistance (AMR) represents one of the main concerns of modern medicine and a challenge for the medicinal chemistry community. The formation of biofilm by many microbial species further contributes to worsening this phenomenon. In biofilms, microbial cells can tolerate stressful conditions, becoming resilient to most antibiotics and increasing the persistence of infections. Hence, anti-biofilm agents represent useful tools in the treatment of infectious diseases, enhancing the effectiveness of traditional antimicrobial agents and preventing resistance mechanisms. In this context, the tryptophan (W)-repressor binding protein A (WrbA) plays a key role in the formation of biofilm in E. coli. However, its specific function is still poorly understood, and only few inhibitors are reported in the literature. Therefore, considering the promising therapeutic potential of interfering with the function of this enzyme, our research group is working towards the development of new WrbA inhibitors as antibiofilm agents. Recently, we identified a pool of natural products showing a high affinity towards WrbA by employing a target-based virtual database screening; the most promising molecules were purchased for biophysical and biological evaluation. The results of these assays allowed us to select a natural scaffold to create a new library of compounds and perform a second virtual screening, leading to five candidate inhibitors that were synthesized and tested. Both the natural and the synthetic compounds were assayed on recombinant E. coli WrbA by MicroScale Thermophoresis (MST), allowing the determination of their dissociation constants (Kd). One of the natural compounds displayed a Kd in the nanomolar range, demonstrating a superior binding affinity to the reference compounds, salicylic and cinnamic acid. On the other hand, the synthesized compounds bound WrbA with Kd values in the low micromolar range. The analysis of their antibiofilm potential revealed very promising activities in both groups. The results of this investigation will be illustrated, along with potential applications in the pharmaceutical field.