Two flavonols from Artemisa annua which potentiate the activity of berberine and norfloxacin against a resistant strain of Staphylococcus aureus.

Bioassay-guided fractionation of an extract of Artemisia annua L. (Asteraceae) was conducted in order to assess the possible presence in the plant material of inhibitors of bacterial multidrug resistance pumps. Fractions were tested for Staphylococcus aureus growth inhibition in the presence of a subinhibitory dose of the weak antibacterial alkaloid berberine. Active fractions yielded the flavones chrysosplenol-D and chrysoplenetin, which themselves had very weak growth inhibitory action, but which made a potent combination with berberine. In comparison with work on other flavonols, it is likely that potentiation is due to the inhibition of an S. aureus multidrug resistance (MDR) pump. These same two flavonols were earlier reported to potentiate the activity of artemisinin against Plasmodium falciparum.