Extraction,Separation And Antioxidant Activity Of Total Flavonoids From Premna Microphylla Turcz Leaves

Premna microphylla Turcz leaves contain not only a large amount of pectin,crude fiber,crude protein,soluble sugar,but also are rich in minerals and flavonoids.Premna microphylla Turcz are abundant in the Jiangyou area of Mianyang City,Sichuan Province.Where there is a traditional custom of using their leaves to process leaf tofu.In order to further understand and utilize the resources of Premna microphylla Turcz in Jiangyou area,this thesis firstly optimized the extraction technology of total flavonoids from Premna microphylla Turcz leaves,then separated and purified it with macroporous adsorptive resin,lastly studied the antioxidant activity.The specific research contents and results are as follows:1.Total flavonoids from Premna microphylla Turcz leaves were extracted by ethanol extraction.On the basis of the single factor experiments,response surface methodology was used to optimize the extraction technology.The results showed that the optimal conditions were as follows:ethanol concentration was 84%,solid-liquid ratio was 1:34 g·mL^-1,extraction temperature was 80?and extraction time was 3.25h.Under these conditions,the extraction rate of total flavonoids was 7.33%.2.The separation and purification of total flavonoids from Premna microphylla Turcz leaves were studied with the macroporous adsorptive resins.First of all,the macroporous adsorptive resins which were suitable for purifying total flavonoids were screened.Then,the sepration and purification conditions of total flavonoids were optimized,considering the main factors affecting the static adsorption of the resin.The results showed that the X-5 of macroporous adsorption resin was suitable for the separation of total flavonoids from Premna microphylla Turcz leaves,and the optimum statci adsorption and desorption conditions were as follows:3 h of adsorption balance time,2 h of desorption balance time,0.6 mg·mL^-11 of sample concentration,4.0 of sample pH value,30?of adsorption temperature and 55?of desorption temperature,95%of desorption ethanol concentration.Under above combined condition,the total flavonoids were brownish-yellow powders with a purity of 85.34%.The major components was probably flavonone obtained from the colour reaction and ultraviolet spectral analysis.3.The antioxidant activity of total flavonoids from Premna microphylla Turcz leaves was studied through determining the scavenging rates of DPPH radical,hydroxyl radical,superoxide anion radical and ABTS cationic free radical,the total antioxidant capacity and reducing power.The results showed that the highest antioxidant activity of total flavonoids was 75%of ethanol concentration.Among each extraction layer,the antioxidant capacity of ethyl acetate extract was strongest,especially the ABTS cation free radical scavenging activity was stronger than that of V_C.Finally,the feasibility and superiority of principal component analysis were determined in antioxidant screening by using correlation coefficient matrix analysis,common factor variance,principal component extraction,antioxidant comprehensive score and sorting,which provided an idea and method for the evaluation and screening of antioxidant activity in foods.