Annona glabra Flavonoids Act As Antimicrobials by Binding to Pseudomonas aeruginosa Cell Walls

Abstract

<i>Pseudomonas aeruginosa</i> is an important pathogen in opportunistic infections in humans. The increased incidence of antimicrobial-resistant <i>P. aeruginosa</i> isolates has highlighted the need for novel and more potent therapies against this microorganism. <i>Annona glabra</i> is known for presenting different compounds with diverse biological activities, such as anti-tumor and immunomodulatory activities. Although other species of the family display antimicrobial actions, this has not yet been reported for <i>A. glabra</i>. Here, we investigated the antimicrobial activity of the ethyl acetate fraction (EAF) obtained from the leaf hydroalcoholic extract of <i>A. glabra</i>. EAF was bactericidal against different strains of <i>P. aeruginosa</i>. EAF also presented with a time- and concentration-dependent effect on <i>P. aeruginosa</i> viability. Testing of different EAF sub-fractions showed that the sub-fraction 32-33 (SF32-33) was the most effective against <i>P. aeruginosa</i>. Analysis of the chemical constituents of SF32-33 demonstrated a high content of flavonoids. Incubation of this active sub-fraction with <i>P. aeruginosa</i> ATCC 27983 triggered an endothermic reaction, which was accompanied by an increased electric charge, suggesting a high binding of SF32-33 compounds to bacterial cell walls. Collectively, our results suggest that <i>A. glabra</i>-derived compounds, especially flavonoids, may be useful for treating infections caused by <i>P. aeruginosa</i>.