The Antimicrobial Effects of Hydro-Extract of Mentha Piperita Lamiaceae Essential Oil Nanoemulsion on Gram-negative Bacteria of Escherichia coli: A Laboratory Study

Since infectious microbial diseases belong to the most common sicknesses in the world, it is necessary to discover and explore new antibacterial materials. Mentha Piperita Lamiaceae is one of the most consumed medicinal plants in the world; having outstanding antimicrobial, pesticide, antiparasitic, antifungal and therapeutic properties. Therefore, aim of this study was to determine the antimicrobial effects of hydroalcoholic extract of Mentha piperita essential oil nanoemulsions against gram-negative bacteria of E.coli. In this laboratory study, Mentha piperita essential oil and tween 80 were mixed by ultrasonification. Then parameters of surfactant concentration, essential oil percentage, and sonication time were studied. The size of nanoemulsion formulations were then analyzed by dynamic light scattering. The antibacterial activity against gram-negative bacteria, i.e. E.coli was studied using 2 different quantitative and qualitative methods of Colony Forming Unit (CFU) and Disc Diffusion Method (DDM), respectively. The results were reported as mean ± standard deviation. The nanoemulsion formulations were obtained in the concentration ranges of 1 to 5 percent Mentha piperita essential oil with the mean droplets size of about 12 nm and antibacterial activity of quantitative method of around 75 percent (based on CFU) and qualitative method of 3.12 mm inhibitory zone diameter around the disc (based on DDM) against gram-negative bacteria of E.coli. The nanoemulsion system was appropriately stable and showed high antibacterial activity against gram-negative bacteria, i.e. E.coli, in which with increasing essential oil concentration, a significant increase in antibacterial activity was observed. Therefore, it seems that synthesized nanoemulsion formulations have remarkable antibacterial activity with nano-scale properties.