Antibiofilm and Antihemolytic Activities of Actinostemma lobatum Extract Rich in Quercetin against Staphylococcus aureus

<i>Staphylococcus aureus</i> biofilm formation is a pivotal mechanism in the development of drug resistance, conferring resilience against conventional antibiotics. This study investigates the inhibitory effects of <i>Actinostemma lobatum</i> (<i>A. lobatum</i>) Maxim extracts on <i>S. aureus</i> biofilm formation and their antihemolytic activities, with a particular focus on identifying the active antibiofilm and antihemolysis compound, quercetin. Seven solvent extracts and twelve sub-fractions were evaluated against four <i>S. aureus</i> strains. The ethyl acetate fraction (10 to 100 μg/mL) significantly hindered biofilm formation by both methicillin-sensitive and -resistant strains. Bioassay-guided isolation of the ethyl acetate extract identified quercetin as the major antibiofilm compound. The ethyl acetate extract was found to contain 391 μg/mg of quercetin and 30 μg/mg of kaempferol. Additionally, the <i>A. lobatum</i> extract exhibited antihemolytic activity attributable to the presence of quercetin. The findings suggest that quercetin-rich extracts from <i>A. lobatum</i> and other quercetin-rich foods and plants hold promise for inhibiting resilient <i>S. aureus</i> biofilm formation and attenuating its virulence.