| Tea is rich in antioxidant ingredients,and has been investigated at various levels.Due to differences in research methods and systems,there are controversies regarding the antioxidant activities of tea and the related chemical constituents.In addition,the comparison and application of the methods are also given much attention for selection and evaluation of the methods themselves,and till now the researches on the antioxidant activity of tea has progressed from vitro tests to cell and animal experiments.Non-alcoholic fatty liver disease(NAFLD)derives from steatosis and the resulting Oxygen stress,lipid peroxidation and inflammatory cytokines involved in the core system of reactive oxygen which further leads to inflammation,necrosis and fibrosis of the liver,and is featured with fat accumulation.Antioxidants may slow down the occurrence of the disease,and tea especially white tea,is worthy of studying in this fields.In this study,white teas including silver needle,white peony,longevity eyebrow(all produced in 2017)and white peony(produced in 2014)were detected respectively on their antioxidant capacity by three methods of removing DPPH free radicals,removing hydroxyl free radicals and metal ion chelation,and on their contents of polyphenol,flavone,TF,TR,TB,caffeine,amino acid and water extract.The correlation between the above ingredients and their antioxidant capacity was investigated,and the three methods of antioxidant capacity detection were compared and analyzed.The aqueous extracts in different concentrations of the four teas were used as the experimental preparations for establishment of the cell model of nonalcoholic fatty liver,and the extracts of selected concentrations were respectively applied to white tea therapeutic and preventive groups which were compared with the simvastatin group,the natural recovery group and the model group in the content of TG and MDA,the SOD activity,the lipid accumulation,and the expression SREBP-Ic,FAS,CPT1A mRNA of L02 cells to explore the effect of white tea on reducing Lipid accumulation in L02 cells and its mecbanism.The results are as follows:1.When compared between the three teas(all produced in 2017)in the contents of water extract,polyphenol,flavone,amino acid,caffeine,TF,TR,TB,the decreasing orders of the above ingredients were white peony>silver needle>longevity eyebrow,silver needle>white peony>longevity eyebrow,longevity eyebrow>white peony>silver needle,silver needle>white peony>longevity eyebrow,silver needle>white peony>longevity eyebrow,longevity eyebrow>white peony>silver needle,longevity eyebrow>silver needle>white peony,longevity eyebrow>white peony>silver needle respectively.Longevity eyebrow was lowest in contents of water extract,polyphenol,amino acid and caffeine,but highest in contents of TF,TR and TB,and its difference significance with silver needle in contents of all the ingredients reached a very high level.The decreasing orders of L*value,a*value and b*value of the three teas were silver needle>white peony>longevity eyebrow,Longevity eyebrow>white peony>silver needle,longevity eyebrow>white peony>silver needle respectively.2.When compared with white peony produced in 2017,white peony produced in 2014 was decreased in contents of amino acid and polyphenol by 1.03%and 1.74%respectively,but higher in contents of caffeine,flavone,TR and TB,and also higher in a*and b*values in great contrast to its lower L*value.3.The methods of removing DPPH free radicals and hydroxyl free radicals indicated the decreasing order of antioxidant ability:C>2017 silver needle>2017 white peony>2017 longevity eyebrow>2014 white peony,but the method of metal ion chelation indicated the following order:EDTA-2Na>2017 longevity eyebrow>2017 white peony>2014 white peony>2017 silver needle.4.When compared between the above three methods in the correlation of their detected antioxidant capacity with the individual ingredient and the chromatic aberration values,the results showed that the methods of removing DPPH free radicals and hydroxyl free radicals were negatively correlated with the content of flavone,TF,TB and b*value among which were most significantly correlated with b*value and TF content with correlation coefficients of 0.914(P<0.01)and 0.939(P<0.01),0.743(P<0.01)and 0.762(P<0.01)respectively;and were positively correlated with the content of caffeine,polyphenol and L*value among which were most significantly correlated with L*value and caffeine content with correlation coefficients of 0.833,0.868 and 0.651,0.609 respectively;the method of metal ion chelation was significantly negatively correlated with the caffeine content with correlation coefficient of 0.933 and was significantly positively correlated with the TF content with correlation coefficient of 0.932.5.When with correlation analysis made between the above three methods the results showed that there was a significant positive correlation between methods of removing DPPH free radical and hydroxyl free radical with correlation coefficient of 0.991(P<0.01),namely the two methods were significantly consistent in the antioxidant capacity so detested;and that the method of metal ion chelation was significantly negatively correlated with the two methods of removing DPPH free radical and hydroxyl free radical with correlation coefficient of-0.632(P<0.05)and-0.665(P<0.05)respectively.6.Treatment of L02 cells with 1 mmol/L oleic acid for 24 h was the most ideal condition for establishment of non-alcoholic fatty liver cell model.7.The contents of TG and MDA in L02 cells indicated the lipid accumulation level and the extent to which the cells are attacked by free radicals,the SOD activity indicated the ability of removing oxygen free radicals,and the expression of SREBP-Ic could promote that of lipogenic genes as FAS etc.and the synthesis of fatty acids,otherwise the expression of CPT1A could accelerate the decomposition of fatty acids.The test showed that the decreasing order was(1)the normal group>the drug group>the natural recovery group>the model group.regarding L02 cell SOD activity;(2)the model group>the natural recovery group>the drug group>normal group regarding L02 cell TG and MDA content;(3)the model group>the normal group>the natural recovery group>the drug group regarding L02 cell FAS and SREBP-Ic expression level;(4)the drug group>the natural recovery group>the normal group>the model group regarding L02 cell CPT1A expression level.Among the therapeutic groups the L02 cell treated with the aqueous extract of 1 mg/mL silver needle showed the highest SOD activity,the lowest MDA content,the lowest proportion of lipid droplets and the lowest expression of SREBP-Ic and FAS but the highest expression of CPT1A.In the tea prevention group,the activity of SOD was the highest,the content of MDA and TG was the lowest at 1 mg/mL,and the activity of SOD was the lowest at 1 mg/mL,while the ratio of lipids was the highest.The MDA and TG contents were higher than natural recovery.In the group,the expression of SREBP-Ic and FAS was highest(higher than that of natural recovery group),while the expression of CPT1A was the lowest(lower than that of natural recovery group).This study revealed that white tea could reduce the lipid accumulation in hepatocytes by ways of inhibiting the expression of SREBP-1c and FAS and the TG synthesis,upgrading CPT1A relative to beta fatty acid oxidization and accelerating the TG decomposition.The treatment with 1 mg/mL silver needle solution showed the most obvious effect,while treatment with 1mg/mL longevity eyebrow solution in the preventive groups indicated opposite effects in those respects,which remained to be further investigated. |
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