Extraction,Purification And Antioxidant Activity Of Polyphenol From Red Raspberry Leaves

Red raspberry(Rubus Ideaus L.)is a small berry in the genus Rubus of Rosaceae.Its fruit is bright in color,sweet and sour and juicy,rich in active ingredients such as polyphenols,flavonoids,ellagic acid and salicylic acid,and has physiological functions such as antioxidant,anti-tumor and anti-aging.It is called “the third generation of fruit”.According to the Compendium of Materia Medica,its root,stem and leaf can be used as medicine.It tastes sweet and smooth,nourishes the kidney,strengthens the essence,and nourishes the liver to improve the eyesight.The red raspberry leaves produced by the planting process are rich in active ingredients such as polyphenols and have high physiological activity.However,they are often discarded in the field,resulting in a waste of resources and reducing the added value of the development of the red raspberry industry.In this study,red raspberry leaves were used as raw materials,and the extraction process of polyphenols was optimized by ultrasound-assisted alcohol extraction method.Under the optimal extraction conditions,the purification process of polyphenols was optimized by macroporous resin method.Finally,the antioxidant activity of different parts of raspberry leaves before and after purification was studied.The main contents and conclusions are as follows:1.Response surface methodology was used to optimize ultrasonic-assisted ethanol extraction of polyphenols from red raspberry leaves.Taking the yield of polyphenols,flavonoids and proanthocyanidins,DPPH,ABTS free radical scavenging ability and iron ion reduction ability of FRAP as response values,Box-Behnken design was used to optimize the main factors affecting the six response values,and the optimal extraction conditions were determined as follows: Ultrasonication temperature was 81?,ultrasonic power was 200 W,volume fraction of ethanol was 40%,ratio of solid to liquid was 1:30g/m L,and ultrasonic time was 29 min.The results showed that the yield of polyphenols,flavonoids and procyanidins were 40.32±0.24 mg/g,27.54±0.31 mg/g,11.89±0.27 mg/g,DPPH free radical scavenging ability was 165.65±0.56 mg TE/g,ABTS free radical scavenging ability was 48.98±0.42 mg TE/g,and FRAP iron ion reducing ability was36.45±0.53 mg TE/g.2.Macroporous resin was used to separate and purify the crude polyphenols.The results showed that DM130 lipid was the best macroporous resin for purification of red raspberry leaf polyphenols.The static experimental data are in good agreement with the quasi-second-order dynamics model and the Langmuir isothermal model.Thermodynamic study shows that the adsorption process is spontaneous,exothermic and physical adsorption,and the disorder degree is reduced.Purification,the optimal conditions of polyphenols resin column are as follows: DM130 of red raspberry leaf polyphenol best purification condition of sample concentration on 6 mg/m L,the sample flow rate of 1.0m L/min,eluent for ethanol solution,the volume fraction of 50%,desorption velocity is 1.0m L/min,after purification of polyphenols from the original 13.07% to 38.15% purity,increased 2.92 times.3.The contents of polyphenols in different parts were higher than flavonoids and higher than proanthocyanidins,and after purification were significantly higher than before.In general,the contents of total phenols and flavonoids in different parts were all upper leaves>middle leaves>lower leaves>stems,while the contents of proanthocyanidin in different parts were stems>upper leaves>middle leaves>lower leaves.In general,the scavenging ability of DPPH and ABTS free radical and the reducing ability of FRAP were stronger than that of crude extract.