Isolation And Identification Of Flavonoid From Broussonetia Papyrifera And Synthesis Of Luteolin Selenium Complex

The Broussonetia papyrifera（B.papyrifera）is a fast-growing tree with a high survival rate,and its leaves,stems and fruits have medicinal and health functions.Flavonoid compounds are important active substances in the B.papyrifera,which have antioxidant,anticancer,anti-inflammatory and immunity enhancement effects.Flavonoids can form complexes with trace elements,which can not only change the physical and chemical properties of flavonoids,but also promote the absorption of trace elements by human body.In this paper,flavonoids of B.papyrifera was isolated and purified,luteolin-selenium complex was prepared and its biological activity was studied.The results are as follows:（1）Flavonoids were extracted from leaves of B.papyrifera by Ultrasonic-assisted extraction.The effects of ethanol concentration,solid-liquid ratio and ultrasonic time on the of flavonoids were investigated.the extraction conditions of flavonoids were optimized by Response surface methodology.The results showed that when the concentration of ethanol was 69%,the ratio of solid to liquid was 1:52 g/m L and the ultrasonic time was 37 min,the maximum extraction rate of xanthone was 37.946 mg/g.Free radical scavenging experiment was used to study the antioxidant activity of flavonoids of B.papyrifera.The scavenging rates of B.papyrifera flavonoids on DPPH and ABTS were 73.03%and 99.54%respectively,indicating that B.papyrifera flavonoids had good antioxidant activity.（2）The flavonoids of B.papyrifera was purified by metal complexation method.Based on the optimal metal salt for the complexation of flavonoids from B.papyrifera,the effects of mass concentration of metal salt solution,p H,complexation reaction time and the concentration of flavonoids of B.papyrifera on the separation and purification of xanthophane by metal complexation were discussed.L₉（3⁴）orthogonal design was used to optimize the process conditions.The results showed that calcium acetate was the ideal complexing metal salt for the purification of xanthophane.When the mass concentration of calcium acetate solution was 10 mg/m L,the p H of sample solution was 10.5,the complexing time was 10 min,and the concentration of xanthophane in crude extract of xanthophane was 0.45 mg/m L,the concentration of xanthophane in crude extract of xanthophane was 0.45 mg/m L.The metal complexing conversion of B.papyrifera flavonoids could reach 89.93%;when 0.3 g EDTA was as reagent to decompose complex,the dissociation rate of the compound reached 83.2%,and the purity of the compound increased by 4.06 times after purification.The purified flavonoids were analyzed by ultra-high pressure liquid chromatography-tandem mass spectrometry,and six flavonoids were detected,which were wild flavanin,flavanin,isobvitaxanthin,quercetin,luteolin and apigenin.（3）Luteolin selenium complex was prepared by acid catalysis and analyzed by SEM,IR,MS,NMR and TGA analysis.Luteolin reacts with selenium to form a stable Se complex,which contains two luteolin molecules and a selenium-oxygen group,which is connected to the sixth carbon of the two luteolin elements.The DPPH radical scavenging activity and antibacterial activity of luteolin selenium complex were investigated.When the concentration of luteolin selenium complex was 3 mg/m L,the DPPH radical scavenging rate was 91.1%.When the concentration of luteolin selenium complex was 5 mg/m L,the inhibition zones for staphylococcus aureus and Escherichia coli were 10 mm and 6 mm,respectively,indicating that luteolin selenium complex had good antioxidant and antibacterial activity.