Extraction,Purification And Physicochemical Properties Of Polysaccharides From Symphytum Officinale L.

Comfrey(Symphytum officinale L.),a perennial herb belonging to Boraginacae,is a high-quality and high-yield forage crop with long utilization period.Comfrey is also used as medicinal plant and represents activities including anti-inflammatory,analgesic,etc.Polysaccharides are polymers that widely distribute in living organisms.In recent decades,polysaccharides have attracted great attention of researchers due to their activities of antioxidant,antiviral,antidiabetic,antitumor,anti-inflammation,immunoregulation,etc.In order to get more information of active ingredients in comfrey,polysaccharides were isolated and purified from comfrey.The physicochemical properties and activities of polysaccharides were studied,which had provided theoretical basis for the exploitation and utilization of comfrey resources.The experimental results were as follow:(1)Four techniques including hot water extracting technology(HW),ultrasonic assistance extracting technology(UA),enzyme assistance extracting technology(EA)and enzyme-ultrasonic assistance extracting technology(EUA)were used to extract comfrey polysaccharides(CPs).The corresponding polysaccharides obtained were named as HW-CPs,UA-CPs,EA-CPs and EUA-CPs,respectively.The results indicated that the contents of total polysaccharide and protein of EA-CPs were significantly higher than those of the other three polysaccharides(P<0.05).UA-CPs had the higher extraction yield(14.36%)and the lower molecular weight.HW-CPs had the higher uronic acid content,ABTS radical scavenging activity and reducing power.(2)Because of the higher ABTS radical scavenging activity and reducing power of HW-CPs,and the lower cost and operability of HW,the response surface methodology was performed to optimize the extraction condition of HW.The optimal conditions to extract the polysaccharides were as follows: liquid–solid ratio(25 mL/g),extraction time(150 min),and extraction temperature(84 ?),allowed a maximum polysaccharides yield of 129.87 mg/g.(3)Hot air drying(HD),vacuum drying(VD)and freeze drying(FD)technologies were used to dry CPs.The corresponding polysaccharides obtained were named as HD-CPs,VD-CPs and FD-CPs,respectively.The yield of polysaccharides,and the contents of total polysaccharides,protein,sulfate and uronic acid of FD-CPs were significantly higher than those of HD-CPs and VD-CPs(P<0.05).FD-CPs had the lower molecular weight,and showed the stronger scavenging capacities against DPPH radical,ABTS radical reducing power than HD-CPs and VD-CPs(P<0.05).Therefore,FD served as an appropriate and effective method to dry CPs.(4)DEAE-Cellulose 52 column and Sepharose CL-6B column were used to isolate and purify CPs,and purified polysaccharide named as CPs-1.2 was obtained.Proteins and nucleic acid were not determined in CPs-1.2 by UV spectrum detection.CPs-1.2 showed a typical peak of polysaccharides absorption through the detection of FT-IR spectroscopy.The molecular weight(3812.39 Da)of CPs-1.2 was determined by Sepharose CL-6B column chromatography.The monosaccharide composition was determined by HPLC.The results showed that CPs-1.2 was composed of galacturonic acid,glucose,galactose and arabinose.The molar ratios these four monosaccharides were 1.00,2.28,1.13 and 0.88.In addition,CPs-1.2 showed notable ?-glucosidase inhibition activity.