Preparation of peppermint oil nanoemulsions: Investigation of stability, antibacterial mechanism and apoptosis effects.

Peppermint oil (PO) is one of the most popular and widely used essential oils. However, due to volatile and poor water solubility of volatile oil, its application in the fields of medicine and food is limited. In order to solve this problem, the high speed shearing technology was used to prepare the nanoemulsion from PO. By using a series of characterization methods, such as turbiscan scanning spectrum, dynamic light scattering (DLS), confocal laser scanning microscope (CLSM), the best nanoemulsion formula was identified as PO 10 %, surfactant 8 % (Tween-60: EL-20 = 3:1) and deionized water 82 % (w/w). The inhibition strength of nanoemulsion on bacteria was evaluated by detecting the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) treated with peppermint oil nanoemulsion (PON) and observing the morphology of bacteria with biological scanning electron microscope (SEM). The results showed that PON had strong inhibitory effect on E. coli. At the concentration range of 0.02 μg/μL-0.2 μg/μL, the apoptosis rate of BEAS-2B cells was less than 10 % compared with control cells. All in all, the PON prepared under this formula is stable, which provides a reference for further exploration of essential oil as natural antibacterial materials in the future.