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Abstract
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Objectives: Despite the considerable potential of herbal essential oils as antioxidants and antimicrobials, some problems such as high volatility of phenolic compounds and low solubility in water causes restrictions in their usage. In order to protect hydrophobic bioactive compounds against environmental adverse conditions and improve their solubility and stability, different encapsulation methods such as nanoencapsulation, microemulsion and nanoemulsion are used. The objective of this study was to formulate tarragon nanoemulsion and investigate its antimicrobial properties. Materials and methods: Oil in water emulsions (O/W) of tarragon EO was formed at ambient temperature by ultrasound method through blending 10 wt% of tarragon EO, 85 wt% water and mixture of 5 wt% surfactants (Tween® 80/Span® 80). Antibacterial activity of tarragon EO and its nanoemulsion (NEO) was evaluated determining minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) using the micro dilution method by 96-well microtitre plates. The bacterial pathogens Staphylococcus aureus (ATCC 29213), Listeria monocytogenes (PTCC 1298), Salmonella entritidis (ATCC 14028), Shigella dysenteriae (ATCC 25922), Escherichia coli (ATCC 25922) were kindly supplied by Department of Microbiology, Faculty of Veterinary Science, University of Tehran (Tehran, Iran). Results: The in vitro inhibitory activities of tarragon EO and its nanoemulsion were as follows: S. aureus (MICEO: 4.25; MBCEO: 5.00; MICNEO: 2.5 and MBCNEO: 3.25 mg/mL), L. monocytogenes (MICEO: 4.75; MBCEO: 5.50; MICNEO: 3.25 and MBCNEO: 3.75 mg/mL),, S. entritidis (MICEO: 6.75; MBCEO: 7.25; MICNEO: 4.75 and MBCNEO: 5.75 mg/mL), Shigella dysenteriae (MICEO: 5.30; MBCEO: 6.10; MICNEO: 3.80 and MBCNEO: 4.45 mg/mL) and E. Coli (MICEO: 7.25; MBCEO: 8.00 MICNEO: 5.75; and MBCNEO: 6.25 mg/mL).
Conclusions: S. aureus and L. monocytogenes (Gram positive) were the most sensitive bacteria against both EO and nanoemulsion, while E.
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