Study On The Extracting,Structural Properties And Activity Of Polysaccharide From Glycyrrhiza

Glycyrrhiza is a perennial plant with good medicinal value and is one of the most widely used medicinal plant in traditional Chinese medicine.The polysaccharide of licorice has many biological activities such as anti-oxidation,anti-inflammation,anti-tumor and the like.In this paper,the extraction conditions of polysaccharides from licorice were optimized by taking the yield of glycyrrhizin as an index,and the extracted polysaccharides of licorice were purified to study the structural characteristics,antioxidant activity and a-glucosidase inhibitory activity.The effects of extraction temperature,extraction time,extraction times and ratio of material to liquid on the extraction yield of licorice polysaccharides were studied by single factor orthogonal experiment with licorice as raw materials.The experimental results show that the optimal extraction conditions of water extraction method were as follows:extraction temperature was 80℃,extraction times was 3 times,extraction time was 2 h,ratio of material to liquid was 1:30(g·mL-1).According to the experimental results,the optimal conditions for the extraction of licorice polysaccharides were tested.The extraction rate of licorice polysaccharide was 4.31 5±0.13%.By hot water extraction,ethanol precipitation,protein removal,pigment removal and freeze-drying,the soluble crude polysaccharide of licorice was obtained.The polysaccharide content was 51.09%.The crude polysaccharide of licorice was purified by Sephadex G-200,and named as GPS.The purity of polysaccharide was 91.00%,the yield was 0.33%,and the molecular weight was 1.96×103kDa.The structure of GPS was analyzed by specific optical rotation,monosaccharide composition,infrared spectrum,periodate oxidation and smith degradation,nuclear magnetic resonance and methylation.The results showed that the specific optical rotation of GPS was+20°,and the monosaccharide composition of GPS was arabinose,glucose and galactose,and the molar ratio was 1:4.048:3.174.The glycosidic linkage of GPS was based on the(1→4)-linked-Glc,(1→6)-linked-Gal and(1→3,6)-linked-Glc as the main chain,(1→3)-linked-Gal,(1→5)-linked-Ara and T-Glc are branched.The Congo red test showed that GPS has a triple helix structure.Scanning electron microscopy results show that surface of GPS showed smooth flake and dendritic structure.The antioxidant activity in vitro of GPS was evaluated by detecting the ability to scavenge free radicals.The results showed that the scavenging ability of GPS against DPPH radical,·OH radical,O2-· radical and ABTS increased with the increase of its concentration.When the concentration of GPS reached 3 mg·mL-1,the scavenging ability of GPS to DPPH radical,·OH radical,O2-· radical and ABTS was 50.75±0.13%,52.32±0.13,25.84±0.35%and 44.57±0.15%,which showed that GPS had antioxidant activity,and the scavenging ability to O2-· free radical was relatively weak.The inhibitory activity of a-glucosidase showed that GPS had inhibitory effect on a-glucosidase,and the inhibitory effect on a-glucosidase was enhanced with the increase of GPS concentration.When the concentration of GPS reached 6 mg·mL-1,the inhibition rate of α-glucosidase activity reached 64.77%.