Preparation And Properties Of Litsea Cubeba Essential Oil Microemulsion

Litsea cubeba essential oil,with abundant yield and strong aroma,is one of the unique plant resources in China.It has antibacterial activity,antioxidant activity,anti-inflammatory,anti-cancer,insecticidal activity and so on.However,Litsea cubeba essential oil has low water-solubility,volatility,and oxidation,which is not only unfavorable to its storage and transportation,but also reduces its bioavailability,limiting its application and the development of its entire industry.The microemulsification of Litsea cubeba essential oil into Litsea cubeba essential oil microemulsion can not only effectively solve the above problems,but also further improve its antioxidant and bacteriostatic activities and extend its action time,which has important practical significance and research value.In this study,the oil-in-water type(O/W type)Litsea cubeba essential oil microemulsion was successfully prepared for the first time by discussing the preparation conditions of Litsea cubeba essential oil microemulsion,which filled the research gap of Litsea cubeba essential oil in microemulsion.Then through the test of its stability,water solubility,viscosity,inclusion rate and other physical and chemical properties,it provides theoretical support for the development and utilization of subsequent products.Finally,by testing its antioxidant activity and bacteriostatic activity,it was found that compared with Litsea cubeba essential oil,Litsea cubeba essential oil microemulsion has better antioxidant and bacteriostatic properties,which provided the research basis for increasing the added value and expanding its application.During preparation of Litsea cubeba essential oil microemulsion by adding-water method,single factor experiment was used to investigate the effect of surfactants,co-surfactants,the ratio of the surfactant to the co-surfactants(Km value)and preparation temperature on the formation of Litsea cubeba essential oil microemulsion.The preparation conditions were further optimized by orthogonal experiment.Based on the results,the optimized conditions were identified as Triton X-100 used as surfactant,anhydrous ethanol used as co-surfactant,the Km value was 2,and the preparation temperature is 25℃.A series of Litsea cubeba essential oil microemulsion with different ratio of mixed surfactant to oil phase(S/O value)and water content were prepared at optimized conditions.The electrical conductivity of the microemulsion was measured.The results showed that for microemulsion with S/O value of 6:4,7:3,8:2,when the water content is less than 60%,the type of microemulsion is water-in-oil type(W/O type),when the water content is between 60%and 70%,the type of microemulsion is mostly double continuous type(B.C type),when the water content is more than 70%,the type of microemulsion is O/W type.For microemulsion with S/O value of 9:1 when the water content is more than 60%,the type of microemulsion is O/W type.The results of temperature stability validated that microemulsion with S/O value of 9:1 showed better temperature stability at the water content of 80%and 90%.Besides,microemulsion with S/O value of 9:1 had better uniform distribution at the water content of 90%.Hence,microemulsion with S/O value of 9:1 and the water content of 90%(sample 1 of Litsea cubeba essential oil microemulsion)was prepared at optimized conditions.Sample 1 of Litsea cubeba essential oil microemulsion has good centrifugal stability.The water-soluble test results showed that the water solubility of Sample 1 of Litsea cubeba essential oil microemulsion is better than that of the essential oil itself,which revealed that microemulsification of Litsea cubeba essential oil benefited to improving the water solubility of essential oil.The results of TEM demonstrated that the microemulsion droplets were spherical and well dispersed.In addition,the physicochemical properties of sample 1 of Litsea cubeba essential oil microemulsion were as follows:average particle size was 16.75 nm,PDI was 0.084,viscosity was 0.038 mPa·s,conductivity was 60.6 μs/cm,and the encapsulation efficiency was 70.1%.The results of 2,2’-Azinobis-(3-ethylbenzthiazoline-6-sulphonate)radical(ABTS+·)scavenging experiments indicated that ABTS+·scavenging rate of sample 1 of Litsea cubeba essential oil microemulsion was significantly higher than that of essential oil in the concentration range of 2 mg/mL～10 mg/mL.The ABTS+·scavenging rate of Litsea cubeba essential oil microemulsion sample 1 at 10 mg/L concentration was 28.93%,while that of Litsea cubeba essential oil was only 6.06%,indicating that Litsea cubeba essential oil prepared as microemulsion can significantly improve its antioxidant properties.In addition,the antioxidant activity of Litsea cubeba essential oil microemulsion sample 1 increased with increasing concentration.The mycelial growth rate method was used to determine the effect of sample 1 of Litsea cubeba essential oil microemulsion on Phytophthora parasitica var.nicotianae,Rhizoctonia solani,and Sphaeropsis sapinea.The results showed that the microemulsion have stronger bacteriostasis than essential oils for the three type of test bacteria.What’s more,Sorting the bacteriostasis of microemulsion agsinst the three type of test bacteria from big to small is Rhizoctonia solani(EC50=1.40)>Phytophthora parasitica var.Nicotianae(EC50=18.21)>Sphaeropsis sapinea(EC50=143.78).