The Antimicrobial Acitivty of Three Species of Echinacea (Asteraceae: Heliantheae)
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Echinacea was identified as a potential medicinal plant native to Missouri and extracts were prepared from the leaves and roots of three species. A priori consideration was given to taxonomic information, phytochemical, ethnobotanical and current research data. Antimicrobial agar disk diffusion and broth microdilution susceptibility testing was used to determine if the extracts had antimicrobial activity, if the species, plant part or concentration had an effect on the antimicrobial activity and to quantitate antimicrobial activity of gram positive and gram negative bacteria and fungi. Echinacea extracts had antimicrobial activity. Echinacea paradoxa extracts had greater activity than E. pallida extracts. Four microbial species tested were susceptible to all extracts tested. Similar activity was indicated for the root and leaf extracts. Twenty mg/mL extract concentrations had greater activity than 10 mg/mL. The microbial spectrum of the Echinacea extracts was broad, with activity against all microbial types; however the activity was less in fungi. All Echinacea extracts had minimum inhibitory concentration values greater than 10 mg/mL against all microbes tested.