| In this study,essential oil from Guanxi pomelo peel was respectively extracted by steam distillation and cold pressure,and the ingredient composition and physical properties between the two essential oils were differentiated.The antioxidant and free radical scavenging properties of Guanxi pomelo essential oil were evaluated by four different chemical detection methods in vitro.B16 melanoma cells were used to study the effect of Guanxi pomelo essential oil and its effect on melanin production.This study provides the basis which can further expand the the application of Guanxi pomelo essential oil in medicine,cosmetics,food industry and other aspects.The main results are as follows:1.Physicochemical characteristics and composition analysis of Guanxi pomelo essential oilThe essential oil of Guanxi pomelo was extracted by steam distillation and cold pressure,and the physicochemical index and composition of the two essential oils were analyzed.(1)The extraction rate by cold pressure method is 0.82%,the essential oil is light yellow clear liquid,the aroma is natural and fresh,the relative density is 0.5691%,the refractive index is 1.4935;the extraction rate by steam distillation is 1.07,the essential oil is colorless clear liquid with a strong aroma of heated grapefruit.The relative density is 0.8435 and the refractive index is 1.4687.(2)31 substances are detected in the cold-pressure oil,21 kinds in hydrothermal oil.d-Limonene,?-Myrcene,Ocimene,?-Pinene,?-Pinene,and citral are detected in the essential oil obtained by the two extraction methods.The essential oils extracted from both methods also have their special labeling components.The total content of the water-hot oil terpene compound is higher than that of the cold-pressure oil,but the oxygen-containing compound is 0.54%lower than that of the cold-pressure oil.The physical and chemical indexes of essential oils obtained by the cold-pressure method and the steam distillation method are similar and the quality is good.2.Analysis of antioxidant properties of Guanxi pomelo essential oilThe antioxidant properties of Guanxi pomelo essential oil were evaluated by DPPH radical scavenging rate,hydroxyl radical scavenging rate,superoxide anion radical scavenging rate and total antioxidant activity.Guanxi pomelo essential oil shows good antioxidant activity and concentration dependent effect.The hydroxyl radical scavenging activity and total antioxidant activity of high concentration essential oil were higher than those of positive control Vc and BHT.The IC50 of hydroxyl radical scavenging rate was 0.88 mg/mL.The free radical scavenging activity of DPPH and superoxide anion radical scavenging activity was lower than that of positive control,but the IC50 of free radical scavenging activity was 79.12 mg/mL and 1.35 mg/mL.3.Whitening effect of Guanxi pomelo essential oil based on B16 melanoma cell evaluation system(1)Guanxi pomelo essential oil with low concentration of 5 ?g/mL had proliferative effect on B16 cells.With the increase of essential oil concentration,cell survival rate decreased significantly.When the essential oil concentration of Guanxi pomelo was 150?g/mL,the cell survival rate was only 29.35%(P<0.05).(2)The morphological changes of B16 cells were observed by Hoechst fluorescence staining.With the increase of essential oil concentration,the number of cell death and fluorescence increased gradually,and the cells showed typical apoptotic state.In the positive control group(kojic acid 500 ?mol/mL),the number of cell death is small,the fluorescence was more homogeneous,and the cells were slightly marginalized.(3)The inhibition rate of melanin in Guanxi pomelo essential oil was determined by NaOH pyrolysis method.The essential oil in the concentration range of 50 ?g/mL?150 ?g/mL significantly inhibited melanin synthesis in B16 cells.When the concentration of essential oil was 150 ?g/mL,melanin production decreased by 50.28%,28.71%lower than that of positive control group(70.53 ?g/mL).(4)The expression of tyrosinase protein was detected by ELISA and Western blot.The inhibitory effect of pomelo essential oil on Tyr activity of B16 cells showed a good dose-effect relationship.The higher the concentration,the smaller the activation rate of Tyr.The inhibition rate of Tyr in Guanxi pomelo essential oil at high concentration was higher than that in positive control group,which suggested that Guanxi pomelo essential oils play a whitening effect by inhibiting the activity of Tyr. |
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