Preparation And Optimization Of Cymbopogon Citratus(DC.) Stapf Essential Oil Microemulsions And Research On Its Antioxidant/Antitumor Activities

Cymbopogon citratus?DC.?Stapf essential oil?C.citratus essential oil?,natural plant extract,has the pharmacological activities of antibacterial,antioxidant,anti-inflammatory and antitumor.However,due to the characteristics of poor stability,high volatility,insolubility in water,etc.,its active components would be damaged,and the active efficacy would be reduced during the storage periods.C.citratus essential oil was analyzed in this study and O/W microemulsion was constructed to improve the essential oil characteristics of water solubility,poor stability,and enhance the bioavailability.The pseudo-ternary phase diagram was used to investigate the influence of the microemulsion system components on the phase behavior to select optimal constituents.Then the antioxidant and antitumor activities of C.citratus essential oil microemulsion?M-EO?was explored.?1?C.citratus essential oil was extracted using steam distillation method and the volatile compounds were analyzed by GC-MS.There were 65 volatile substances identified in C.citratus essential oil.Aldehydes,alcohols and alkene were the main substance,accounting for36.07%,32.06%and 8.82%separately.The four highest content components were D-citronellal?35.69%?,geraniol?16.56%?,citronellol?12.66%?and D-limonene?3.77%?.?2?The optimized recipe of M-EO was obtained and the phase characteristic was studied using conductivity method and rheological method.The O/W microemulsion was prepared by using Tween 80 as surfactant,anhydrous ethanol as cosurfactant,and the mass ratio of surfactant to co-surfactant was K_m=3:1,the mass ratio of mixed surfactant to essential oil was S_mix=8:2,the moisture content was 70%.The particle size was about 16.50 nm,and the PDI value was about 0.47.?3?DPPH,ORAC,and PSC methods were used to analyze the antioxidant activity of the M-EO with moisture content of 70%?O/W?,50%?B.C?,and 15%?W/O?respectively.In the DPPH experiment,the reaction rate of M-EO was higher than C.citratus essential oil.Only the O/W M-EO performed a stronger DPPH radical scavenging activity than essential oil.In the DPPH scavenging capacity test,the EC₅₀ value of C.citratus essential oil was significantly lower than that of the O/W M-EO.In the water-soluble system of ORAC and PSC methods,the antioxidant activity of M-EO with 70%water content was better than C.citratus essential oil?the ORAC value and PSC value of essential oil were 0.35?mol TE/mg and 1.53?mol VE./g,the value of M-EO were 1.94?mol TE/mg and 32.15?mol VE/g,respectively?.In the experiments to compare the antioxidant activity in different storage time and store temperature,the results of the three methods showed the antioxidant activity of M-EO did not change obviously within one month.M-EO was more suitable storing at room temperature rather than 4?condition.?4?The antitumor activities of C.citratus essential oil and M-EO with 70%,50%moisture content were researched using human hepatoma cells HepG2 and breast cancer cells MDA-MB-231.All the essential oil and M-EO had inhibitory effect on the two tumor cell lines,and the M-EO with 70%moisture content had the strongest activity,then was the M-EO with 50%moisture content,the C.citratus essential oil had the weakest effect.The cell morphology was affected by different doses of the M-EO with 70%moisture content acting on,and developing into malformation or rupture eventually.The activity of M-EO stored at room temperature had no significant change against HepG2 cells after a month of storage,while the activity against MDA-MB-231 cells was slightly reduced.The M-EO stored at room temperature showed a better tumor cell inhibitory activity than that of storing at low temperature conditions.Then the flow cytometry experiment showed the M-EO with 70%moisture content could induce the apoptosis of HepG2 and MDA-MB-231 cells in a dose-dependent manner.