Ultrasonic-assisted Extraction,Purification And Antioxidant Activity Of Polysaccharides From Evening Primrose(Oenothera Biennis L.) Leaves

The evening primrose was rich in the northeast of China.People mainly study evening primrose oil at present.The use of the by-products like stems,leaves were discarded or burned.It is not only a waste of resources,but also a pollution of the environment.The leaves of evening primrose contain flavonoids,phenols,polysaccharides and other bioactive ingredients.The application of by-products is promising if they are used as raw materials to make other products.The main purpose of this study was to optimize the polysaccharide which was extract from evening primrose assisted by ultrasonic.Purified the crude polysaccharide and preliminary analysed the properties and structure of the sample.The antioxidant activity of crude polysaccharide and purified polysaccharide were also studied.After that,we made a kind of beverage products of polysaccharides.This research was in order to improve the utilization rate of by-product from evening primrose.The main contents and conclusion of this paper were as follows:(1)Based on the single factor experiments and the response surface design,an optimized regression model for ultrasonic extraction of polysaccharides from evening primrose leaves was established.The optimal extraction conditions were as follows: ultrasonic power 400 W,liquid-solid ratio 23:1(mL/g),ultrasonic time 36 min and ultrasonic temperature 53 ?.Under the above conditions,the yield of polysaccharides was 3.54%.The relative error was only 2.21% compared with the predicted value under the modified condition,which indicated that the optimized data was accurate and reliable.(2)Compared two deproteinized methods of polysaccharides from evening primrose: Sevage method and three chloroacetic acid method and choose the better one.And then it was detected by UV scanning.The crude polysaccharides were purified by DEAE-52 column chromatography and then we dealt with the sample by dialysis and freeze-drying.After that,the properties of polysaccharides from evening primrose were measured and the content of uronic acid was determined.The study of HPLC indicated that the purified polysaccharides with a main molecular weight of 5435 Da.The study of Fourier transform infrared spectroscopy showed that the purified polysaccharides had the characteristic structure of polysaccharides.The polysaccharide was determined by gas chromatography-mass spectrometry(GC-MS).It was composed of arabinose,mannose,galactose,talose and some unknown components.(3)The reducing power,total antioxidant capacity,DPPH radical scavenging capacity,ABTs radical scavenging capacity and hydroxyl radical scavenging capacity of crude polysaccharide and purified polysaccharide were studied.The results showed that the antioxidant activities of polysaccharides became stronger with the increase of concentration.What was more,the antioxidant activity of crude polysaccharide was better than purified simple.The antioxidative properties of polysaccharides were good.(4)The sour and sweet tasted polysaccharide beverage from evening primrose was made by optimizing the process.The formula was as follows : polysaccharides from evening primrose leaves for 0.04mg/mL,7% for xylosic alcohol,3% for honey and 0.07% for citric acid.