In Vitro Study of Biological Activity of Teucrium Davaeanum Extracts on Strains of Pathogenic Bacteria

Abstract

The major purpose of this study was to recognize the role of different extraction techniques (decoction, Soxhlet, and soaking) and solvents (water, ethanol, ethyl acetate, ether, and chloroform) on the antimicrobial activities of extracts of Teucrium davaeanum. These solvents were examined to determine the conditions for which extracts with a higher content of bioactive compounds. The Kirby-Bauer disk diffusion method was used to assess in vitro antimicrobial activity of the different crude botanical extracts against Gram-positive (Staphylococcus aureus) and -negative (Escherichia coli and Pseudomonas aeruginosa). The antibiotics Gentamycin, Ciprofloxacin, and Azithromycin were used for antimicrobial susceptibility tests. The microbial growth was determined by measuring the diameter of the zone of inhibition and the mean values are presented with ± S.E.M. The ethyl acetate extract showed the highest inhibition diameter of 20±1 mm at a concentration of 0.1 g/mL against S. aureus, so it is considered to have higher efficacy than Ciprofloxacin, which showed an inhibition diameter of 15 mm. The isolated essential oil is also showed powerful inhibition effect with a diameter of 12±2 mm against S. aureus and 10±2 mm towards P. aeruginosa at a concentration of 0.1 g/mL, so it is a higher antimicrobial effect than Gentamycin and Azithromycin, which showed an inhibition diameter of 10 mm. The cold aqueous extract afforded an inhibiting diameter of 7 mm against S. aureus at a concentration of 0.1 g/mL, so it is considered to be less effective compared to the antibiotics that used as control. Moreover, hot water showed a low inhibitory effect on E. coli with 3±1 mm at a concentration of 0.1 g/mL. The results of applying ethanol extract showed an inhibitory effect on S. aureus only with 4±1 mm, otherwise, the results of applying chloroform extract and diethyl ether showed no inhibitory effect. Therefore, the most active extract was ethyl acetate extract, followed by volatile oil and then the cold aqueous extract. This could be attributed to the higher content of bioactive compounds in both extracts of ethyl acetate extract and essential oil.