In silico screening and in vitro validation of phytocompounds as multidrug efflux pump inhibitor against E. coli

Multiple drug resistance (MDR) in bacteria has increased globally in recent times. This has reduced the efficacy of antibiotics and increasing the rate of therapeutic failure. Targeting efflux pump by natural and synthetic compounds is one of the strategies to develop an ideal broad-spectrum resistance-modifying agent. Very few inhibitors of AcrB from natural sources have been reported till date. In the current study, 19 phytocompounds were screened for efflux pump inhibitory activity against AcrB protein of E. coli TG1 using molecular docking studies. The molecular dynamics simulation provided stability the protein (AcrB) and its complex with chlorogenic acid under physiological conditions. Moreover, the detailed molecular insights of the binding were also explored. The Lipinski rule of 5 and the drug-likeness prediction was determined using Swiss ADME server, while toxicity prediction was done using admetSAR and PROTOX-II webservers. Chlorogenic acid showed the highest binding affinity (-9.1 kcal mol(-1)) with AcrB protein among all screened phytocompounds. Consequently, all the phytocompounds that accede to Lipinski's rule, demonstrated a high LD50 value indicating that they are non-toxic except the phytocompound reserpine. Chlorogenic acid and capsaicin are filtered out based on the synergy with tetracycline having FIC index of 0.25 and 0.28. The percentage increase of EtBr fluorescence by chlorogenic acid was 36.6% followed by piperine (24.2%). Chlorogenic acid may be a promising efflux pump inhibitor that might be employed in combination therapy with tetracycline against E. coli, based on the above relationship between in silico screening and in vitro positive efflux inhibitory activity. Communicated by Ramaswamy H. Sarma.