Extraction And Enrichment Of Vitexin And Its Glycosides From Phyllostachys Edulis Leaves

A recent study found that vitexin?VT?,vitexin-4''-O-glucoside?VG?and vitexin-2''-O-rhamnoside?VR?are abundant in P.edulis.Recent medicinal research indicates that VT and its derivatives have antiviral,antibacterial,antioxidant,anti-inflammatory,antitumor,blood pressure-lowering,and anti-spasmodic pharmacological activities.Extracting these target compounds from P.edulis is therefore receiving attention.HPLC was used to analyze the VG,VR,and VT contents of the extraction solutions.Ionic liquid–lithium salt pretreatment followed by ultrasound-assisted extraction was applied to extract target compounds from samples.Macroporous resin was successfully applied on enrichment of VG,VR,VT and the recycle of ionic liquid was explored.High-performance liquid chromatography?HPLC?method for analysis and quantification of the VG,VR,and VT in P.edulis leaves was established.The mobile phase comprised a tetrahydrofuran:acetonitrile:methanol:0.5%acetic acid?17.1:1.7:1.2:80 by volume?mixture.The mobile phase flow rate was 1.0 m L/min,an injection volume of 10?L was used,and the column temperature was 25?.VG,VR,and VT were determined by measuring the change in absorbance at 360 nm over a running time of 40 min.Under these conditions,the three compounds were separated and analyzed by their retention time and peak area ratios.The regression lines for VG,VR,and VT were Y_VG=1325311 X+82981,R²=0.9998;Y_VR=14785006 X-11993,R²=0.9997;Y_VT=17806012 X-47414,R²=0.9998;where Y is the peak area of analyte,and X is the concentration of analyte?mg/m L?.The optimum conditions for the proposed extraction process are identified as follows:7.5 mmol 1-butyl-3-methylimidazolium bromide and 0.066 g lithium chloride are mixed,dissolved,diluted with 10m L acetonitrile?to decrease the system viscosity?,and then uniformly and rapidly mixed with1.0 g air-dried leaf sample.The acetonitrile and moisture are removed by rotary evaporation at110?and-0.09 MPa vacuum for 30 min and 15 mL of water is added,to reduce the concentration of C4mimBr to 0.5 mol/L,and the suspension is then extracted for 5 min under250 W ultrasound irradiation.The total flavonoid yield is 638?g/g?VG:319±18?g/g;VR:206±6?g/g;VT:113±3?g/g?with an error of 27?g/g.The optimal enrichment and separation conditions for VG,VR,and VT with HPD600macroporous resin were as follows:Adsorption part:feed volume 20 BV;flow rate 2 BV/h;temperature 25?.Gradient elution:20%ethanol 2 BV,then 80%ethanol 4 BV;flow rate 2BV/h.The concentrations of VG,VR,and VT in the product were 1.66%,2.08%and 1.17%.