| Tea polyphenol is a substance with polyhydroxy structure in plant cells,which has many functions such as anti-oxidation and anti-aging.Tea polyphenols are the main active ingredients in Rizhao green tea.In this study,the tea polyphenols in Rizhao green tea were extracted,and the antioxidant activity of tea polyphenol extracts was evaluated by in vitro antioxidant evaluation methods.The in vivo effects and mechanisms of rat liver injury models induced by lipopolysaccharide were evaluated.The test mainly includes the following five aspects:?1?Tea polyphenols were extracted by ethanol extraction.The effects of extraction conditions on the extraction rate of tea polyphenols were studied,and the optimal extraction conditions were obtained.The effects of ethanol concentration,extraction time,extraction temperature,and liquid-solid ratio on the extraction rate of tea polyphenols were studied using a single factor test.Then use orthogonal experiments to optimize the extraction conditions:The ethanol concentration was 50%and extraction time was 40 min,The extraction temperature was 65?,and the liquid-solid ratio was 20:1.After verification,the extraction rate was 13.54%.?2?Tea polyphenols were extracted by compound enzyme extraction.The effects of extraction conditions on the extraction rate of tea polyphenols were studied,and the optimal extraction conditions were obtained.The effects of compound enzyme ratio,liquid-solid ratio,pH value,enzymatic hydrolysis temperature,enzymatic hydrolysis time on polyphenol extraction rate were studied using a single factor test.Using response surface model,the extraction rate of tea polyphenols was taken as the response value,and the enzymatic hydrolysis time,enzymatic hydrolysis pH,and enzymatic hydrolysis temperature were taken as variables,to determine the optimal extraction combination:enzymatic hydrolysis time was 79 min,enzymatic hydrolysis pH was 5.3 and the enzymatic hydrolysis temperature was 58?.At this time,the extraction rate can reach a maximum of 24.03%.?3?Tea polyphenols were extracted by ultrasonic-assisted extraction.The effects of extraction conditions on the extraction rate of tea polyphenols were studied,and the optimal extraction conditions were obtained.The effects of extraction time,ultrasonic power,liquid-solid ratio,ethanol concentration,temperature on polyphenol extraction rate were studied using a single factor test.Using response surface model,the extraction rate of tea polyphenols was taken as the response value,and the extraction time,ultrasonic power,liquid-solid ratio were taken as variables to determine the optimal extraction combination:The extraction time was 23 min,the ultrasonic power was 505 W,and the liquid-solid ratio was 26:1.At this time,the extraction rate reached a maximum of 33.79%.?4?The antioxidant capacity of tea polyphenol extracts was investigated using an in vitro antioxidant assay.By measuring the DPPH·,OH·,ABTS·,O2-·removal rate of the tea polyphenol extract,the antioxidant ability of the tea polyphenol extract was evaluated.The results show that the Rizhao green tea polyphenols extract has a strong ability to remove DPPH·,OH·,ABTS·and has a certain O2-·removal ability.?5?Study the antioxidant effect of tea polyphenols extract in rats.In order to study the protective effect of tea polyphenol extracts on lipopolysaccharide?LPS?-induced Wistar rat oxidative damage,the rat model of liver injury was established by using lipopolysaccharide oxidation to induce oxidative stress in rats.Rats were divided into normal group,model group,drug group,low-medium-high-dose group.After 8 weeks of feeding,the viability of SOD,GSH-Px,CAT and MDA content in liver tissue homogenate were measured;the content of IL-1?,IL-6,IL-10,IL-12 and TNF-?in serum were measured.The DPPH·,OH·,O2-·scavenging ability of rat serum were measured.The results showed that compared with the model group,the SOD,GSH-Px and CAT activities of tea polyphenol extracts in the low,medium and high dose groups were significantly increased?P<0.05?.The effect of the high-dose group is particularly obvious;while the MDA of the low--dose,medium-dose,and high-dose group is significantly reduced?P<0.05?,and the effect of the high-dose group is better.The content of TNF-?,IL-1?,IL-6,IL-12 in the middle and high dose group was significantly lower than that in the model group?P<0.05?;the effect of the high dose group was better.The IL-10 in the middle and high dose groups was significantly higher than that in the model group,and there was no significant difference between the two groups?P>0.05?.Therefore,tea polyphenols extract plays an important role in inhibiting oxidative damage in rat liver. |
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