Evaluation of antimicrobial activity of macroemulsion and nanoemulsion of Salvia chorassanica essential oil against pathogenic and food spoilage microorganisms

In this study, chemical compounds of Salvia chorasanica essential oil were identified by GC-MS method. Then, nanoemulsion of essential oil was prepared by ultrasound method and the stability of its particle size during two weeks of storage was evaluated by DLS at room temperature. The antimicrobial activity of macroemulsion and nanoemulsion of S. chorasanica essential oil against six pathogenic bacteria and three food spoilage molds was investigated by microdilution method. The results showed that the essential oil had 20 different chemical compositions. The particle size of the nanoemulsion increased from 91.83 to 193.61 nm during two weeks. The nanoemulsion form of the essential oil had higher antimicrobial effect than its macroemulsion against all the studied microorganisms. Also, the antimicrobial activity of macroemulsion and nanoemulsion of essential oil on gram-positive bacteria was more than gram-negative. Among the pathogenic bacteria, the gram-positive bacterium Bacillus cereus indicated the highest sensitivity to the nanoemulsion of essential oil and had the lowest MIC, 3.125 µl/ml. In addition, MIC and MFC of essential oil nanoemulsion against all three molds were determined to be 6.25 µl/ml and 12.5 µl/ml, respectively. Thus, a lower effective concentration of essential oil in the form of nanoemulsion will be required to control food microorganisms and prevent the effects of the use of high concentrations of essential oil.