Preparation And Antibacterial Properties Of Nanoemulsion Of Plant Essential Oils From Different Species

Natural plant oil is a natural aromatic product obtained from raw plant materials and has a wide range of biological activities.The main challenges in the use of natural plant essential oils as antimicrobial agents are low stability and volatility.Formulating natural plant essential oils into nanoemulsions could be a way to improve their performance and practical application in food.This paper selects natural plant essential oils derive from three different species,such as peppermint oil,cinnamaldehyde,and tea tree oil.They were prepared as nanoemulsions and the optimal prescriptions for the nanoemulsions were screened.The properties,antimicrobial properties,and mechanisms of action of nanoemulsions were studied,and their safety at different cellular levels was evaluated.The following results are:(1)Peppermint oil is one of the most popular and widely used essential oils.Through Turbiscan Lab? Scanning analysis,dynamic light scattering,confocal laser scanning microscope and series of characterization methods,the best nanoemulsion formulation was peppermint oil at 10%w/w,surfactant at 8%w/w(Tween-60:EL-20=3:1)and deionized water at 82%(w/w).The levels of ROS and MDA in S.aureus and E.coli treated with peppermint oil nanoemulsion were detected,and the morphology of bacteria was observed by SEM.The results showed that peppermint oil nanoemulsion had strong inhibitory effect on E.coli and weak inhibitory effect on S.aureus.Therefore,0.02 ?g/?L-0.2 ?g/?L in peppermint oil nanoemulsion,in the range of concentration,the apoptosis rate of BEAS-2B lung cells were 10%lower than the control cells.In conclusion,the peppermint oil nanoemulsion prepared according to the formula is stable,which provides a reference for further exploring peppermint oil as a natural antibacterial material in the future.(2)Cinnamaldehyde has strong biological activity and an obvious killing effect on foodborne pathogens.The best formula of cinnamaldehyde nanoemulsion was screened out,and analyzed by the Malvern particle analyzer,confocal laser scanning microscope and Turbiscan Lab?.The cinnamaldehyde nanoemulsion was characterized by scanning analysis.The results showed that the best formula was cinnamaldehyde at 6%w/w,surfactant EL-90 at 10%w/w and deionized water at 84%w/w.The droplet size of cinnamaldehyde nanoemulsion is diminutive,up to 48 nm,and the droplet distribution is uniform.The fluctuation of the multiple light scattering spectrum of cinnamaldehyde nanoemulsion is quite stable.It was found that cinnamaldehyde nanoemulsion had strong antibacterial activity against E.coli and S.aureus due to its lipophilicity and oxidative stress.The minimum bactericidal concentration of E.coli is 0.5 mg/?L.Compared with E.coli,cinnamaldehyde nanoemulsion had less inhibitory effect on S.aureus.We also found that cinnamaldehyde nanoemulsion had high cytocompatibility with L02 hepatocytes.The survival rate of the control group was 96.7%,the total apoptosis rate was 3.25%,and the concentration of treated group were 0.05?g/?L?0.15 ?g/?L and 25.0?g/?L the survival rates of L02 cells in were 95.6%,95.1%and 86.3%,respectively.The results of this study provide an effective reference for the development of food antimicrobial agents in the future.(3)The antibacterial properties of a tea tree oil is the best among the essential oils and is a potential natural antibacterial agent.Through Turbiscan Lab? Scanning analysis,dynamic light scattering,confocal laser scanning microscope and a series of characterization methods,the best tea tree oil nanoemulsion formulations were identified as tea tree oil at 10%w/w,surfactant Tween-40 at 8%w/w and deionized water at 82%w/w.The optimal tea tree oil nanoemulsion particle size is 134 nm,the nanoemulsion droplets are evenly distributed and stable,and the multiple light scattering spectrum is stable at the content of surfactant of at 8%w/w.It has been found that tea tree oil nanoemulsion has strong antibacterial activity against E.coli and S.aureus.The bacteria are treated with the same mixture of tea tree oil,Tween-40 and deionized water without shear,and the sterilization effect is far less than that of tea tree oil nanoemulsion.Compared with E.coli,tea tree oil nanoemulsion had less inhibitory effect on S.aureus.In addition,tea tree oil nanoemulsion has high Biosafety to L02 hepatocytes.The survival rates of the control group and each concentration treated group are more than 90%.When the concentration of tea tree oil nanoemulsion is 0.05 ?g/?L,the survival rate was 93.3%,which is almost the same as that in the control group.In concentration 0.25 ?g/?L,the survival rate of hepatocytes was 90%.The total apoptosis rate of hepatocytes were less than 10%at all experimental concentrations.The results showed that tea tree oil nanoemulsion had high safety.Finally,the stability and safety problems of nanoemulsion were studied.The conclusion is that natural plant nanoemulsion can become a candidate and substitute for common synthetic antibacterial agents in practical pharmaceutical and food systems.The results of this study are great significant for the design and application of plant essential oil nanoemulsion as a potential antibacterial agent in medicine and food industry.