Chilean medicinal plants traditionally used for wound healing therapy studied for activity against resistant Staphylococcus aureus strains
Plants traditionally used for wound healing therapy by the Huilliche people in Chile were investigated for their activity against a selection of Staphylococcus aureus strains. S. aureus is a frequently encountered pathogen in skin infections and ethnopharmacological knowledge on treatment of infected wounds may prove valuable in the search for anti-staphylococcal compounds.
30 plant samples of 24 species were collected in the Valdivian rainforest west of Osorno in Chile. Material was extracted with three different organic solvents and antibacterial activity against susceptible and resistant S. aureus was evaluated. An agar-overlay diffusion assay and a MIC-determination were utilized for comparative purposes. Total phenolics and tannins were determined and antibacterial contribution of the tannins evaluated.
Extracts of 19 species were active against susceptible S. aureus at 100µg extract. At the same concentration 16 species showed activity against resistant S. aureus. Extracts without tannins rendered only six samples active. The MIC-determination showed antibacterial activity of 20 extracts on all eight strains, and the highest effect was 64µg/ml. Species Aristotelia chilensis (Mol) Stuntz, Baccharis magellanica (Lam.) Pers., Baccharis sphaerocephala Hook et Arn., Berberis buxifolia Lam. and Crinodendron hookerianum Gay being among the most active. Activity against multidrug resistant Vanthida strain was remarkable with 36 active extracts.
The results support Huilliche traditional knowledge, and the hypothesis that their wound healing plants are potential sources of anti-staphylococcal agents. These results will form the basis for a selection of plant species for further investigation of new antibacterials in the fight against resistant pathogens.
Acknowledgement: Robert Leo Skov, SSI, the National Reference Center in Denmark, for strains and helpful advice. Arife Önder and Betül Asar for technical support and Sara Nilean for valuable knowledge during plant collection.