In Vitro Antibacterial Activity of Selected Medicinal Plants Traditionally Used in Iran Against Plant and Human Pathogenic Bacteria

Medicinal plants are widely used for the treatment of different plant diseases and hospital infections caused by bacteria. The present study aims at determining the in vitro antibacterial activity of the medicinal plants traditionally used in Iran against the bacterial species associated with plant diseases and hospital infections. The antibacterial usefulness of methanol extracts of five medicinal plants is tested against seven Gram-negative bacteria and three Gram-positive bacteria using the agar disc diffusion method. Some of the plant extracts showed antibacterial activity against Gram-positive bacteria and Gram-negative bacteria. The high antibacterial activity against the Gram-positive species and Gram-negative was in the extract of Geum urbanum against Bacillus subtilis (+++) and Pseudomonas aeruginosa (+++). Consequently, plant Geum urbanum was subjected to gas chromatography-mass spectrometry (GC-MS) analysis. Results show that its antibacterial activity may be due to the presence of eugenol, phenolic acid and tannin. The present study finds clear evidence supporting the traditional use of the plants in treating plant diseases and hospital infections related to bacteria. These plant species showed a moderate to a high antibacterial activity against the bacteria tested.