Preparation Of Mesona Chinensis Benth Essential Oil Microemulsions And Research On Its Stability And Bioactivities

Mesona Chinensis Benth is an annual herb of the Lamiaceae family and a species in the genus Platostoma.M.Chinensis is rich in resources and low in price in China,but its processing and utilization is low.Mesona Chinensis Benth essential oils(M.EO)is a natural secondary metabolite with high value and many potential bioactivities.However,its poor water solubility and stability limit its application.In this paper,the chemical composition of M.EO was analyzed and M.EO microemulsion(M.EO-ME)was prepared.The effects of components and ratios on the formation of M.EO-ME were studied.The dilution,storage and in vitro digestion stability of M.EO-ME were evaluated,and the antioxidant and antiproliferative activities of M.EO and M.EO-ME were compared.The main results of this paper are as follows:(1)M.EO was extracted by hydrodistillation and characterized by GC-MS analysis.The major compounds were alloaromadendrene(25.53%),?-caryophyllene(19.31%),isocaryophyllene(11.30%),?-humulene(8.30%)and eremophilene(7.62%).A pseudo ternary diagram was constructed to study the effects of components and ratios on the formation of microemulsion,a M.EO-ME system with Tween 60 as surfactant,ethanol as co-surfactant,K_m=2:1 and S_mix=8:2 was obtained,and found that microemulsion had good stability for ionic strength and p H.The electrical conductivity and viscosity changes of M.EO-ME and the diffusion of methylene blue dye solution showed that the transition of W/O microemulsions with water content from 0-30%to bicontinuous structures at a water content of 30-60%,after more than 60%of water content,the structures transited to O/W microemulsions.(2)After M.EO-ME was diluted multiple times,the particle size became smaller,the distribution was more concentrated,and it had good dilution stability.During storage at room temperature and 4?for 60 days,the particle size and PDI of the M.EO-ME fluctuated within a small range,indicating that M.EO-ME had good storage stability.In in vitro digestion experiments,it was found that the particle size,PDI,p H value and electrical conductivity of M.EO-ME in the oral and gastric phases changed little,while the corresponding indexes in the intestinal phase changed markedly.The microscopic morphology of M.EO-ME was characterized by transmission electron microscopy,and it showed that the particle size of the oral phase and the gastric phase were close to the initial state,with a good spherical profile,while some amorphous-shaped structures appeared in the intestinal phase image,and the particle size increased.In in vitro release experiment,M.EO-ME had a certain degree of release of M.EO in the oral and gastric phase,while the release rate of M.EO increased significantly in the intestinal phase.The above results indicated that M.EO-ME had good stability in oral phase and gastric phase,but had a targeted release in the intestinal phase.(3)The antioxidant activity of M.EO and M.EO-ME were evaluated by five different antioxidant assays,including DPPH radical scavenging activity,ABTS radical scavenging activity,reducing power assays,oxygen radical absorbance capacity(ORAC)and peroxyl radical scavenging capacity(PSC).In DPPH and ABTS assays,the antioxidant activity of M.EO was slightly increased.In reducing power,ORAC and PSC assays,the antioxidant activity of M.EO was significantly increased by 17%,2.6 times and 8.4 times,respectively,indicating that microemulsification could improve the antioxidant activity of M.EO.(4)Three tumor cell lines(Hep G2,A375,and MDA-MB-231 cells)were selected to compare the antiproliferative activity of M.EO and M.EO-ME.The results showed that microemulsification technology could significantly enhance the antiproliferative activity of M.EO against three tumor cell lines.The effects of M.EO-ME on the cell cycle and apoptosis of MDA-MB-231 cells were study by flow cytometry.It turned out that the percentage of G0/G1 phase cells and total apoptotic cells increased significantly,which indicated that M.EO-ME could arrest the cell cycle of MDA-MB-231 cells in G0/G1 phase and induce apoptosis.The effect of M.EO-ME on the expression of proliferation related genes in MDA-MB-231 cells was investigated with RT-q PCR technology,and it was found that the antiproliferation mechanism of M.EO-ME may be as follows:one is to downregulated the expression of Cyclin E and CDK2 to interfere with transition from G0/G1 phase to S phase in the cell cycle.The second is to downregulated the expression of PI3K,AKT and Bcl-2,upregulated the expression of BAD,induced cell apoptosis through PI3K/AKT/BAD/Bcl-2 signaling pathway.