| Fingered citron(Citrus medica L.var.sarcodactylis Swingle)is a variation of Citrus genus Citrus,which has extremely high ornamental value,medicinal value and abundant economic value.Fingered citron essential oil is clear,colorless liquid,lighter in density than water,and its aroma is extremely rich,with the unique taste of citrus plants.The essential oil has lots of biological activities such as anti-oxidation,anti-microbial,anti-parasitic,anti-tumor,anti-inflammatory,anxiolytic and anti-depressant.The optimum extraction process of the essential oil was determined,and formula and process of fingered citron essential oil nanoemulsion prepared by high pressure homogenization were explored.Moreover,the antibacterial and antitumor activities of both of fingered citron essential oil and its nanoemulsion were also studied.It provided theoretical basis for the development and application of Jinhua fingered citron essential oil.The results were as follows:(1)Fingered citron essential oil was extracted by hydrodistillation method(HD)and enzymatic assisted hydrodistillation,taken by extraction rate as evaluation index.The results were as follows: The optimum process for extracting fingered citron essential oil by hydrodistillation was: Liquid ratio 1:4,adding 2.0% NaCl,distillation 3.0 h,and the essential oil yield was 1.26%;Enzymatic assisted hydrodistillation optimal conditions: pH 5.0,50°C water bath enzymatic hydrolysis 1.0 h,fingered citron essential oil yield was 1.13%.The main components of essential oils were detected by GC-MS combined with retention index method.The results showed that the main components of fingered citron essential oils were D-limonene and γ-terpinene.(2)Fingered citron essential oil nanoemulsion(O/W)was prepared by high-pressure homogenization using fingered citron essential oil and MCT mixed as the oil phase and Tween-80 as the surfactant.To obtain the optimum process of nanoemulsion,we took the particle size and PDI(Polydispersity Index)as evaluation indicators.The results showed the particle size was 112.53±2.25 nm,PDI was below 0.3 under following conditions,ie: 10 wt% oil phase(mass ratio of fingered citron essential oil and MCT 4: 1)and 2.0 wt% emulsifier homogenization pressure 69 Mpa and homogenization 3 times.The nanoemulsion prepared by this method was preferable stable.(3)Oxford cup method was used to investigate the common pathogenic bacteria such as Campylobacter jejuni,Escherichia coli,Salmonella typhimurium,Listeria monocytogenes,Staphylococcus aureus and Candida albicans;Norfloxacin solution was used as a positive control to determine the minimum inhibitory concentration(MIC)of fingered citron essential oil and its nanoemulsion.The results showed that fingered citron essential oil and its nanoemulsion had good inhibitory effects on Escherichia coli and Staphylococcus aureus.It also had certain inhibitory effects on Candida albicans and Campylobacter jejuni,and the inhibitory effect of nanoemulsion group was more obvious than that of pure essential oil group.(4)The inhibitory effect of fingered citron essential oil and its nanoemulsion on the proliferation of human colon cancer cells(HT-29 cells)was also investigated.Inverted microscope was used to observe the cell morphology;MTT assay was used to detect the effect of nanoemulsion on the inhibition of cell proliferation;apoptosis was observed by flow cytometry.The results showed that fingered citron essential oil and its nanoemulsion had a significant inhibitory effect on the proliferation of HT-29 cells and was dose-dependent.Moreover,at higher concentrations,the inhibitory effect of nanoemulsion was higher than that of pure fingered citron essential oil(P<0.05). |
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