Antimicrobial activity of Otostegia persica Boiss. extracts

Plants produce a diverse array of secondary metabolites, many of which have antimicrobial activity. Otostegia persica Bioss. (Labiatae) grows in south east of Iran. No previous investigation on antimicrobial effects of this plant has been reported. Thus, the aim of this work was to examine the antimicrobial effect of O. persica extracts with different polarity on several microorganisms. Aerial parts of O. persica were collected from Sistan-Baluchestan province (Iran). Powdered aerial parts of the plant were extracted with ethanol. The extract was concentrated under reduced pressure. The dried extract was extracted with hexane, followed by chloroform and methanol, respectively. Antimicrobial activities of three extracts were tested on several microorganisms using well plate method, MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) methods. O. persica extracts showed antimicrobial activity against Gram positive strains including Listeria monocytogens, Enterococcus fecalis, Staphylococcus aureus, and Staphylococcus epidermidis with MIC values from 0.62 to 20 mg/ml. The MBC values were identical, two, four or eight times higher than MIC values for the corresponding MIC for extracts. The Gram negative strains; Escherichia coli, Pseudomonas aeruginosa, Salmonella spp., Klebsiella spp., and Proteus spp. were not inhibited by O. persica polar, semi-polar, and non-polar extracts. It can be concluded that the tested extracts of O. persica exhibit significant antibacterial activity. This investigation supports the idea of using O. persica extracts as a candidate for further antimicrobial and phytochemical researches.