Study On Extraction And Antioxidant Activity Of Flavonoids From Fig Leaves

Figs(Ficus carica Linn.)are perennial deciduous trees which grow in temperate regions.As a species,they belong to the Ficus moraceae and have bulbous fruit,thick,nearly equal length and width blades.The fig trees have a long history of cultivation and high nutritional value,and they’ve always been the source of nutrition for human survival.The fruit are often used to treat diseases such as anorexia,abdominal distension and pain,hemorrhoids,constipation,indigestion,insufficient milk,sore throat,cough and excessive sputum.However,the current development and utilization of figs in our country is mainly focused on fruit consumption,and fig leaves that have a large biomass are often discarded,resulting in a waste of resources.In this study,fig leaves measured as raw materials and extracted the flavonoids from fig leaves by ultrasonic enzyme-assisted combined with aqueous two-phase extraction(UEAATPE),then extraction parameters by response-surface methodology were optimized,the study used gradient extraction of different polarities to study the antioxidant activity of different extracts.Based on the HPLC-DPPH-MS method,we screened of flavonoids with antioxidant activity online,and combined with mass spectrometry data and other information for the structure identification and analysis of flavonoids.The antioxidant components of flavonoids were extracted from fig leaves by ultrasonic enzyme-assisted combined with aqueous two-phase extraction.Through single factor experiment and BBD response-surface analysis,according to single factor experiment,we screened out 4 factors.It has shown the significant influence on the yield of total flavonoids from fig leaves by single factor design experiment.In the study,we selected 38%ethanol-18%ammonium sulfate two-aqueous-phase system by corresponding surface analysis,used 20:1(mL/g)as the optimal liquid-solid ratio condition,and set 30 min as the optimal ultrasonic extraction time.The yield of total flavonoids was 60.22 mg/g.We compared the total flavonoid content and antioxidant activity in different parts of polar gradient extracts.Under the extraction conditions of petroleum ether,ethyl acetate,n-butanol and water in sequence,we found that the ethyl acetate part had obvious enrichment advantages over the other three extraction parts.In the experiment of scavenging free radicals(such as:DPPH,ABTS+,OH-,superoxide anion),the activity of ethyl acetate part was the highest.In the determination of reducing capacity,FRAP total antioxidant capacity,lipid peroxidation inhibition rate,ORAC oxygen radical absorption capacity,the strongest activity capacity is also the ethyl acetate part.After the study on the correlation between the total flavonoid content of fig leaves and the antioxidant activity,the total flavonoid content of the extracts from each part of the fig leaf showed a positive correlation with the antioxidant activity.In this study,HPLC-DPPH-MS/MS method was used to efficiently screen and id entify antioxidant components in fig leaves.On the basis of single factor experiment s,we optimized the online screening method.The best conditions for HPLCi sample separation chromatography are:0.1%formic acid-acetonitrile,wavelength of 330 nm and the flow rate is 0.7 mL/min.The optimal conditions for HPLC2 are:50 μg/mL DPPH met-hanol solution and a flow rate of 0.5 mL/min.According to mass spectr ometry data,cleavage rules and related literature,we identified the active ingredients in the ethyl acetate extract part,figured out 1 polyphenolic compound and 11 flavon oids contained in fig leaves by analysis,and determined their chemical structures.Th ey are respectively:chlorogenic acid,3-O-[α-L-rhamnopyrano-syl-(1->6)-β-D-glucopyr anosyl]-7-O-(β-D-glucopyranosyl)-quercetin,2-carbox-yl-1,4-naphthohydroquinone-4-O-β-D-glucopyranoside,luteol-in 6-c-β-D-glucopyranoside,8-c-α-L-arabin-opyranoside,schaf toside,isoorientin,isoschaftoside,rutin,2"-O-Rhamnosylvitexin,isovitexin,isoquerceti n,kaempferol-3-rutinoside.Finally,we screened out 12 negative peak antioxidant acti ve substances from the ethyl acetate extract of fig leaves.Among them,peak of 1,2,7,8 are the main antioxidant active substances,which have been identified as chl orogenic acid,3-O-[α-L-rhamnopyra-nosyl-(1->6)-β-D-glucopyranosyl]-7-O-(β-D-glucopy ranosyl)-quercetin,isochafotaside,rutin,respectively.