<i>Lycopus europaeus</i>: phenolic fingerprint, antioxidant activity and antimicrobial effect on clinical <i>Staphylococcus aureus</i> strains

<div><p><i>Lycopus europaeus</i> L. leaves water extract (LEL) was subjected to phytochemical analysis, and evaluated for its antibacterial and antioxidant effects. Antibacterial activity testing was performed on <i>Staphylococcus aureus</i> clinical strains from catheter-related and skin infections by broth microdilution test. LEL showed bactericidal activity at concentrations from 2500 to 5000 μg/mL against all, including methicillin resistant and polyresistant nosocomial, strains. Antioxidant activity was examined using DPPH and ABTS (11.3 and 9.8 μg/mL, respectively) and by ferric reducing ability of the plasma method (891 μmol AAE/g dry extract). Phytochemical analysis of LEL was performed by LC-DAD-MS/MS. Ten phenolic compounds were identified; two minor compounds (glucopyranosyl rosmarinic acid and sagerinig acid) have not been described in <i>Lycopus</i> yet. The major compounds, considered to be responsible for biological activities detected in the study, were determined as rosmarinic acid (76 mg/g) and luteolin-7-<i>O</i>-glucuronide (23 mg/g). <i>L. europaeus</i> arises from our study as a promising source of antibacterial agent for topical usage.</p></div