Abstract
The popular herbal remedy goldenseal (Hydrastis canadensis L.) is traditionally used to treat skin infections. With this study, we show activity
of H. canadensis extracts in vitro against methicillin-resistant Staphylococcus aureus (MRSA). An extract from H. canadensis leaves demonstrated more potent antimicrobial activity than the alkaloid berberine
alone (MICs of 75 µg/mL and 150 µg/mL, respectively). LC-MS detected alkaloids and
efflux-pump inhibitory flavonoids in the extract, and the latter may explain the enhanced
efficacy of the extract compared to berberine alone. We also show evidence of anti-virulence
activity as a second mechanism by which H. canadensis acts against S. aureus. The H. canadensis leaf extract (but not the isolated alkaloids berberine, hydrastine, and canadine)
demonstrated quorum quenching activity against several clinically relevant MRSA isolates
(USA300 strains). Our data suggest that this occurs by attenuation of signal transduction
through the AgrCA two-component system. Consistent with this observation, the extract
inhibited toxin production by MRSA and prevented damage by MRSA to keratinocyte cells
in vitro. Collectively, our results show that H. canadensis leaf extracts possess a mixture of constituents that act against MRSA via several
different mechanisms. These findings lend support for the traditional application
of crude H. canadensis extracts in the prevention of infection.
Key words
Hydrastis canadensis
- Ranunculaceae - quorum quenching - berberine - methicillin-resistant
Staphylococcus aureus
- anti-virulence
