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.
