Purpose: To determine the chemical composition and anti-biofilm activity of burdock leaf fractions
against
Staphylococcus aureus
Methods: The anti-biofilm activity of burdock leaf fractions obtained by column chromatography against
S. aureus was determined by minimum inhibitory concentration (MIC). Scanning electron microscopy
was employed to further investigate the inhibitory activity. Analysis of the chemical composition of the
fractions was performed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS).
Results: The 20 and 34 % ethanol fractions each inhibited the formation of biofilm by
S. aureus, with
half maximal inhibitory concentration (IC
50) ranging from 110 to 150 μg/ml. The 70 % ethanol elution
fraction exhibited the strongest inhibitory activity against biofilm formation with IC
50 of 13 μg/ml. The
minimum inhibitory concentration of the 70 % ethanol fraction completely inhibited the formation of
biofilm at a concentration of 0.5 mg/ml, which was lower than the MIC for the growth of the test
bacterium (1.25 mg/ml). Scanning electron microscopy (SEM) showed that there was no biofilm
formation for cultures treated with burdock leaf fraction, thus confirming the inhibitory efficiency of
burdock leaf fraction against biofilm formation. UPLC-MS data identified five active compounds, namely,
:caffeic acid, p-coumaric acid, cynarin, quercetin and luteolin.
Conclusion: The biofilm formation inhibitory effect of burdock leaf was not only due to its inhibitory
effect on bacterial growth but appear to be influenced by its effect on bacterial surface hydrophobicity,
and aggregation. Thus, the leaf fractions may be useful in the control of biofilms.
