Cyprus St. John’s Wort, Hypericum repens L.: Major Constituents, Antioxidant, Antimicrobial, and Anticholinesterase Activities

Chemical analysis of the hydroethanolic <i>Hypericum repens</i> L. extracts was performed using the LC/Q-TοF/HRMS technique. The majority of compounds identified belonged to phenolics, particularly flavonoids. The extract was also studied for its possible bioactivities, demonstrating high antioxidant properties compared to the control (IC₅₀ values ranging from 4.6 to 9.42 μg/mL). Significant antibacterial activity was also detected against <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, <i>Enterococcus faecalis,</i> and <i>Salmonella enteritidis,</i> with MIC values from 125 to 625 μg/mL. <i>S. aureus</i> presented the highest susceptibility among all bacteria tested. Additionally, the extract showed very mild anticholinesterase activity in the AChE and BChE inhibition assays. These findings provide the first insights into the phytochemical composition, as well as the antioxidant, antimicrobial, and anticholinesterase activities of <i>H. repens</i> extract, suggesting that the endemic Cyprus <i>H. repens</i> is a valuable natural rich source of bioactive compounds with a potentially broad range of bioactivities.