The interaction of plant flavones with amphotericin B: Consequences for its pore-forming ability.

The growth of antibiotic resistance to antifungal drugs contributes to the search for new ways to enhance their effectiveness and reduce toxicity. The undeniable advantage of polyene macrolide antibiotic amphotericin B (AmB) which ensures low pathogen resistance is its mechanism of action related to the formation of transmembrane pores in target lipid membranes. Here, we investigated the effects of plant flavones, chrysin, wogonin, baicalein, apigenin, scutellarein, luteolin, morin and fisetin on the pore-forming activity of AmB in the sterol-enriched membranes by electrophysiological assays. Сhrysin, wogonin, baicalein, apigenin, scutellarein, and luteolin were shown to decrease the AmB pore-forming activity in the bilayers composed of palmitoyloleylphosphocholine independently of their sterol composition. Morin and fisetin led to the increase and decrease in the AmB pore-forming activity in the ergosterol- and cholesterol-containing bilayers respectively. Differential scanning microcalorimetry of the gel-to-liquid crystalline phase transition of membrane forming lipids, molecular dynamics simulations, and absorbance spectroscopy revealed the possibility of direct interactions between AmB and some flavones in the water and/or in the lipid bilayer. The influence of these interactions on the antibiotic partitioning between aqueous solution and membrane and/or its transition between different states in the bilayer was discussed.

Triggering the Amphotericin B Pore-Forming Activity by Phytochemicals.

The macrolide polyene antibiotic amphotericin B (AmB), remains a valuable drug to treat systemic mycoses due to its wide antifungal activity and low probability of developing resistance. The high toxicity of AmB, expressed in nephropathy and hemolysis, could be partially resolved by lowering therapeutic AmB concentration while maintaining efficacy. This work discusses the possibility of using plant polyphenols and alkaloids to enhance the pore-forming and consequently antifungal activity of AmB. We demonstrated that phloretin, phlorizin, naringenin, taxifolin, quercetin, biochanin A, genistein, resveratrol, and quinine led to an increase in the integral AmB-induced transmembrane current in the bilayers composed of palmitoyloleoylphosphocholine and ergosterol, while catechin, colchicine, and dihydrocapsaicin did not practically change the AmB activity. Cardamonin, 4'-hydroxychalcone, licochalcone A, butein, curcumin, and piperine inhibited AmB-induced transmembrane current. Absorbance spectroscopy revealed no changes in AmB membrane concentration with phloretin addition. A possible explanation of the potentiation is related to the phytochemical-produced changes in the elastic membrane properties and the decrease in the energy of formation of the lipid mouth of AmB pores, which is partially confirmed by differential scanning microcalorimetry. The possibility of AmB interaction with cholesterol in the mammalian cell membranes instead of ergosterol in fungal membranes, determines its high toxicity. The replacement of ergosterol with cholesterol in the membrane lipid composition led to a complete loss or a significant decrease in the potentiating effects of tested phytochemicals, indicating low potential toxicity of these compounds and high therapeutic potential of their combinations with the antibiotic. The discovered combinations of AmB with plant molecules that enhance its pore-forming ability in ergosterol-enriched membranes, seem to be promising for further drug development in terms of the toxicity decrease and efficacy improvement.