Phytochemicals increase the antibacterial activity of antibiotics by acting on a drug efflux pump.
Bottom Line: In silico screening was used to predict the bioactivity of plant compounds and to compare that with the known EPI, phe-arg-β-naphthylamide (PAβN).Subsequently, promising products have been tested for their ability to inhibit efflux.We demonstrated the feasibility of in silico screening to identify compounds that potentiate the action of antibiotics against drug-resistant strains and which might be potentially useful lead compounds for an EPI discovery program.
Affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, United Kingdom.Show MeSH
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Mentions: An EPI must also be able to reduce the level of extrusion of efflux pump substrates (Lomovskaya et al. 2001). We used the inhibition of Nile Red efflux to determine the ability of the natural products to reduce efflux pump activity (Bohnert et al. 2010). Nile Red is only weakly fluorescent in aqueous solutions, but undergoes a significant increase in fluorescent quantum yield when in nonpolar environments such as the cell membrane. Cells were preloaded with Nile Red in the absence or presence of the natural products. Once the cells were energized by the addition of glucose, the efflux of Nile Red could be observed as a drop in fluorescence. All the compounds tested were able to inhibit Nile Red efflux to an extent (Fig. 5). Plumbagin was the most efficient and complete inhibition of Nile Red efflux was observed using 50 μmol/L of plumbagin. At much higher concentrations (500 μmol/L), mangiferin was also able to inhibit the efflux, presumably through competition for the binding site, which would again be supportive of mangiferin being a low-affinity substrate rather than an inhibitor (Fig. 5).
Affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, United Kingdom.