New insights into the underlying mechanism involved in the Frangula alnus antivirulence potential directed toward Staphylococcus aureus

Staphylococcus aureus is a leading cause of persistent infections which are difficult to treat due to its biofilm formation capability and increased resistance to available drugs. Our previous research showed the high antibiofilm potential of the ethyl-acetate extract of Frangula alnus and its main component emodin against S. aureus so this study was conducted to elucidate the mechanism behind the observed activity. The main goal of this research was to examine the inhibitory effect of F. alnus ethyl-acetate extracts and emodin on S. aureus biofilm matrix components (exopolysaccharides and eDNA), persister cells, and the staphyloxanthin pigment. It was demonstrated that both substances significantly reduced the production of exopolysaccharides and the amount of eDNA, and decreased the number of persister cells in the studied strains and isolates. However, the effect on staphyloxanthin production was less pronounced, with emodin being more effective. Based on the obtained results, it could be concluded that both the ethylacetate extract of F. alnus and emodin are good candidates for novel antibiofilm agents acting on S. aureus biofilm at different levels.