Screening of Natural Products and Derivatives for the Identification RND Efflux of Pump Inhibitors

Aim and objective: Overexpression of efflux pumps belonging to the Resistance Nodulation cell Division (RND) family is the most important intrinsic resistance mechanism of Pseudomonas aeruginosa. Hence, it is imperative to identify suitable efflux pump inhibitors (EPI) that can lead to increased intracellular concentration of antibiotics by blocking the pump. This study was undertaken to identify a putative plant based efflux pump inhibitor for RND efflux pump of P. aeruginosa. Material and method: Using molecular docking approach, 328 secondary plant metabolites have been screened for their inhibitory activity against cytoplasmic exporter protein MexB of MexAB-OprM efflux pump of P. aeruginosa. After the initial in silico screening, the shortlisted compounds were subjected to in vitro test for efflux pump inhibitory activity using double disc synergy test. A combinatorial library of 1000 molecules was generated from active p-coumaric acid and docked with MexB protein to find a suitable EPI with better binding efficacy compared to the p-coumaric acid. Results: Preliminary screening resulted in five plant-based natural products with significant docking score and were subsequently subjected to double disc synergy test. p-Coumaric acid, amongst the five, was found to potentiate activity of ciprofloxacin in MexAB-OprM overexpressing P. aeruginosa strain. Library compound 482, i.e 4-(4-((Z)-2-carboxy-2-((Z)-2,3-dihydrobenzo[e][1,4]diazepin-l-yl)-1-(4-hydroxyphenyl)vinylamino) phenylsulfonamido)-2-hydroxybenzoic acid, a derivative of p-coumaric acid exhibited the highest docking score of-42.1030 Kcal/mol, which was much higher than parent compound (-17.9403 Kcal/mol) and also known EPI, MC-207,110 (-28.0960 Kcal/mol). Conclusion: p-Coumaric acid and its derivative, 4-(4-((Z)-2-carboxy-2-((Z)-2,3-dihydrobenzo[e][1,4] diazepin-l-yl)-1-(4-hydroxyphenyl)vinylamino)phenylsulfonamido)-2-hydroxybenzoic acid may be used as potential lead molecules for effective RND efflux pump inhibition in P. aeruginosa.