Antimicrobial Assessment of Extracts of Garlic, Onion, and Pelargonium sidoides Chasity Eisenhart Department of Biological Sciences, York College of Pennsylvania Garlic extracted with water was effective against all microorganisms tested The Pelargonium extract showed the lowest MIC against S. aureus (other than AMP) The Pelargonium extract also appeared to encourage growth of S. cerevisiea Conclusions: Extraction method had a direct impact on efficacy of plant extracts. The three plants tested in this study vary widely in efficacy levels against various microorganisms indicating the likelihood of different active antimicrobial components. Active antimicrobial component of garlic extract is likely not allicin, as the extract treated with BME was still effective Literature Cited: Amagase, H Clarifying the real bioactive constituents of garlic. Journal of Nutrition 136: Benkeblia, N Antimicrobial activity of essential oil extracts of various onions (Allium cepa) and garlic (Allium sativum). Lebensmittel Wissenschaft & -Technologie/Food Science & Technology 37(2): Groppo, F., Ramacciato, J., Motta, R., Ferraresi, P., and Sartoratto, A Antimicrobial activity of garlic against oral streptococci. International Journal of Dental Hygiene 5(2): Rahman, M Allicin and Other Functional Active Components in Garlic: Health Benefits and Bioavailability. International Journal of Food Properties 10(2): Introduction:  Herbs, spices, and other plants contain naturally occurring chemicals which can function as antimicrobial agents.  Onions, garlic, and Pelargonium sidoides have all been shown through multiple different studies to be effective against various bacteria (both Gram-positive and Gram-negative) and some fungi (Benkeblia 2003, Rahman 2007, Groppo et. al. 2007).  The method of extraction (drying technique and solvent) has a large impact on chemical composition of the extract and thus on efficacy of the extract (Amagase 2006). Objectives:  Determine an effective method for making plant extracts -Most effective solvent and drying technique  Determine whether the plant extracts have an effect on microorganisms -Which extract has a greater inhibitory effect -Do some plant extracts affect different microorganisms differently? Gram+ vs. Gram- Methods: Freeze dry plant material for 24 hours Powder dried plant material 24 hour extraction using 5 different solvents (acetone, ethanol, methanol, DMSO, distilled water) Antimicrobial assay against S. aureus Antimicrobial assays of effective extracts against various microorganisms ReplicationTesting for active component Table 1. Average Minimum Inhibitory Concentrations (MIC) of garlic extracted with water, onion extracted with methanol, and Pelargonium sidoides extract against various microorganisms Figure 5. A representation of an antimicrobial assay using a 96-well micro titer plate. Numbers indicate determinations of turbidity. Figure 1. The effect of a garlic extract prepared with water on Staphylococcus aureus, Escheria coli, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. Results are averages of three replicates. P. aeruginosa Figure 2. The effect of an onion extract prepared with methanol on Staphylococcus aureus, Escheria coli, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. Results are averages of three replicates. Figure 3. The effect of a commercially available extract of Pelargonium sidoides (Umcka® Cold Care) on Staphylococcus aureus, Escheria coli, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. Results are averages of two replicates. Figure 4. The effect of an antibiotic control, ampicillin, on Staphylococcus aureus, Escheria coli, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. Results represent one data set. Results: a Mean MIC b Only one of three trials showed inhibition c One trial only d Represents one standard deviation from the mean ExtractMicroorganism Inhibitory Result MIC a SD d Garlic H 2 O S. aureus (+) B. cereus (+) E. coli (-) P. aeruginosa (-) S. cerevisiae (yeast) Onion Methanol S. aureus (+) B. cereus (+)- - - E. coli (-) P. aeruginosa (-)+b+b S. cerevisiae (yeast) 0 -- Pelargonium sidoides S. aureus (+) B. cereus (+)+b+b E. coli (-) P. aeruginosa (-)+b+b S. cerevisiae (yeast) --- AMP S. aureus (+) c B. cereus (+) c E. coli (-) c P. aeruginosa (-) c S. cerevisiae (yeast) 0-c-c