A comparison of the anti-staphylococcus aureus activity of extracts from commonly used medicinal plants

Background: Resurgences of Staphylococcus aureus infection continue globally, with antibiotic resistance increasing dramatically, making these infections more difficult to treat. S. aureus epidemics impose public health threats, and economic burdens on health care costs worldwide, presenting challenges modern medicine struggles to control. Objective: In order to answer today's call for effective treatments against S. aureus, we evaluated and compared various botanical extracts that have historically been suggested as useful for their antimicrobial properties against S. aureus. Design: Briefly, S. aureus cultures were treated with selected botanical extracts and the minimum inhibitory concentration (MIC) determined. In addition, to obtain more quantitative measures on bacterial growth, 24-hour growth studies were done to examine the temporal activity and stability of various botanicals on bacterial replication. Results: The antimicrobial activity observed for the botanical extracts used in this comparative evaluation of efficacy included both bacteriostatic and bacteriocidal activity against S. aureus. Highly effective botanicals including Salvia officinalis, Eucalyptus globulus, Coleus forskohlii, Coptis chinensis, Turnera diffusa, and Larrea tridentata exhibited MIC values ranging from 60 to 300μg/mL and a 10⁶-fold reduction in bacterial replication. Arctostaphylos uva-ursi and Allium sativum were slightly less effective, exhibiting MIC values ranging from 90 to 400μg/mL and a 10 ⁵-fold reduction, while Anemopsis californica gave MIC value of 360μg/mL and a 10⁴-fold reduction in bacterial replication. Many botanicals, especially at lower doses, had an initial inhibitory effect followed by a recovery in bacterial replication. Such botanicals included E. globulus, C. chinensis, T. diffusa, A. californica, and Berberis vulgaris. Conclusions: Our data demonstrate that S. officinalis, E. globulus, C. forskohlii, A. uva-ursi, C. chinensis, T. diffusa, A. californica, A. sativum, and L. tridentata all show promising direct antimicrobial activity against S. aureus. For many of these botanicals, strong bacteriocidal activity was observed at higher concentrations, but even at lower concentrations, bacteriostatic activity was evident. Other botanicals including B. vulgaris, Baptisia tinctoria, and Glycyrrhiza glabra showed moderate activity against S. aureus, while Schisandra chinensis, Echinacea angustifolia, and Polygonum multiflorum were shown to be ineffective.