This study was undertaken to assess the antibacterial potential of a polyphenolic compound (+)-lariciresinol isolated from Rubia philippinensis against selected foodborne pathogens Staphylococcus aureus KCTC1621 and Escherichia coli O157:H7. (+)-Lariciresinol at the tested concentrations (250 μg/disk) evoked a significant antibacterial effect as a diameter of inhibition zones (12.1-14.9 mm) with minimum inhibitory concentration (MIC), and minimum bactericidal concentration values of 125-250 and 125-250 μg/mL, respectively. Furthermore, (+)-lariciresinol at MIC showed reduction in bacterial cell viabilities, efflux of potassium (K+) ions and release of 260 nm materials against E. coli O157:H7 and S. aureus KCTC1621. Moreover, deteriorated cell wall morphology of E. coli O157:H7 and S. aureus KCTC1621 cells treated with (+)-lariciresinol at MIC further confirmed its inhibitory effect against the tested pathogens, suggesting it to be an alternative means of antimicrobials.
Keywords: (+)-lariciresinol; Rubia philippinensis; antimicrobial effect; foodborne pathogens; scanning electron microscopy.