Extraction,purification and antioxidant activity of total flavonoids from Premna microphylla Turcz leaves

On the basis of the single factor experiment,this article firstly adopted response surface methodology to optimize the extraction technology of total flavonoids from Premna microphylla Turcz leaves,then screened macroporous adsorptive resins which were suitable for extracting total flavonoids,at last made the preliminary identification and analyzed free radical scavenging activity of them.The results showed that the optimal conditions of the ethanol extraction were as follows: ethanol concentration for 84%,solid- liquid ratio for 1 ∶ 37( g / m L),temperature for 81 ℃ and time for 3.4 h. Under these conditions,we could get 7.29% of the total flavonoids.Meanwhile,the macroporous adsorptive resin X- 5 was suitable for the separation of total flavonoids. The colour reaction and UV- vis spectrum exhibited that dihydroflavone was probably the major components. The DPPH radical and hydroxyl radical scavenging rate of the premna leaves flavonoids increased with the increasing of the concentration and the IC50 values were 0.10 mg / m L and 0.13 mg / m L,respectively. When the concentrations were0.2 mg / m L and 0.4 mg / m L. The DPPH radical and hydroxyl radical scavenging rate were 83.75% and 80.08%,respectively,which were close to that of tert- butyl hydroxy anisole. These data suggested that flavonoids from premna microphylla turcz leaves were developed as antioxidant or raw materials of health food.