Study Of Extraction,Purification And Antioxidant Activity Of Proanthocyanidins From Nitraria

In this study,the Nitraria from Dongying,Shandong Province were used as raw materials to be extract,purify,analyze the components and the antioxidant activity of proanthocyanidins.Ultrasound-assisted organic solvent was used for extraction.The effects of extraction time,extraction temperature,solid-liquid ratio and ethanol concentration on the extraction efficiency were studied to determine the optimal extraction conditions.Five different types of macroporous resins were screened by static adsorption and analytical experiments.The best resin model was AB-8,and further static and dynamic adsorption and analysis experiments were carried out using AB-8 macroporous resin.The composition of proanthocyanidins in fresh fruits and extracted samples of Nitraria were determined by HPLC-MS.The composition of proanthocyanidins during extraction were seen by comparison.Finally,experiments on the stability and antioxidant activity of the Nitraria proanthocyanidins were carried out.In the extraction experiment,the effects of extraction time,extraction temperature,ethanol concentration and solid-liquid ratio on the extraction of proanthocyanidins from Nitraria were studied.The optimal extraction conditions were as follows: the ethanol concentration was 74%,the extraction time was 60 min,the the extraction temperature was 45?,and the ratio of material to liquid was 14 mL /g.According to this condition,the verification experiment was carried out,and the average value of the proanthocyanidins content was 17.045 mg/g,which was only4.47% from the predicted theoretical value.The proanthocyanidin extract was purified by using macroporous resin.Five kinds of macroporous resins were evaluated by static adsorption and desorption experiments.The adsorption rate and resolution of macroporous adsorption resin were considered comprehensively.Finally,the macroporous adsorption resin suitable for separation and purification of Nitraria proanthocyanidins was selected as AB-8.In the static adsorption and analytical experiments,the adsorption rate of the resin to the Nitraria proanthocyanidins at 25? was significantly higher than that at 10?,and the adsorption rate reached the maximum at pH=4.0,so chose pH=4.0 and the temperrature 25?.Subsequent adsorption experiments were carried out under the conditions.Through dynamic adsorption and analytical experiments,the results showthat the optimal conditions are: loading flow rate was 75 mL/h,loading volume was50 mL,eluent volume was 200 mL,analytical solution concentration was 60%ethanol solution,analytical solution volume was 50 mL,analytical solution flow rate was 75 mL/h.The proanthocyanidins from Nitraria fresh fruits and the samples were detected by HPLC-MS.The results showed that the Nitraria proanthocyanidins contained five component: proanthocyanidins A1,A2,A3,B2 and B3.The comparison of the integrated peak area between the Nitraria fresh fruits and the samples shows that the content of dimer proanthocyanidin in the extract is significantly increased,indicating that the dimer extraction effect is better,while the dimer proanthocyanidin is the most widely used and has the best health care function,so the extract has higher value.The stability and antioxidant activity of the Nitraria proanthocyanidins were tested.The results of proanthocyanidins stability experiments showed that the overall change of proanthocyanidin content decreased at different temperatures and different pH conditions.The higher the temperature,the greater the concentration change.The higher the pH,the greater the concentration decrease.The experiments of ABTS,DPPH,OH radical and total antioxidant capacity show that the ability of to scavenge free radicals as follows:proanthocyanidin standard> proanthocyanidin samples >ascorbic acid.The greater the concentration of proanthocyanidins,the stronger free radical scavenging and antioxidant capacity.