Antibacterial and antibiofilm properties of dichloromethane fraction of extracts from adventitious roots of Eurycoma longifolia against Staphylococcus aureus

Adventitious root (AR) cultures of Eurycoma longifolia are the alternative plant materials. However, the biological effects of the ARs are rarely investigated, leading to a delay in their practical application. In this study, antibacterial activities of sub-fractions of E. longifolia ARs extracted by different organic solvents were examined. Furthermore, antibacterial mechanism and antibiofilm effect of the dichloromethane fraction (DCM) against Staphylococcus aureus were explored. Results showed that petroleum ether, DCM, ethyl acetate, and n-butyl alcohol fractions inhibited growth of the tested bacterial species, and the highest inhibitory effect was observed in DCM against S. aureus with a minimum inhibitory concentration of 0.25 mg/mL. DCM promoted the leakage of cell contents of S. aureus, indicating cell permeability increased. After DCM treatment, S. aureus respiration was inhibited, and the activity of a key enzyme in hexose monophophate pathway (HMP) decreased, suggesting an involvement of DCM in regulating the HMP. DCM possessed the ability of scavenging S. aureus biofilm; nearly 50% biofilm was scavenged at 0.5 mg/mL DCM, at which the extracellular polysaccharides and proteins of the biofilm structure were reduced. The findings of this study indicate that DCM can be expected to be used in the production of food or pharmaceutical products.