Extraction,Structure Characterization And Antioxidant Activity Of Polysaccharide From Portulaca Oleracea L

Portulaca oleracea L is a common medicinal herb.Modern pharmacology has shown that it has various biological activities such as anti-oxidation,anti-tumor and immune regulation.It has been isolated a polysaccharide component with anti-tumor,antioxidant,anti-diabetic activities from Portulaca oleracea L.However,the structural characteristics and antioxidant activity of polysaccharides from Portulaca oleracea L have not been studied in depth.In this study,the polysaccharide was extracted from Portulaca oleracea L by "water extraction and alcohol precipitation" at 4℃.The extraction process was optimized by single factor test and L9(34)orthogonal test.Sephadex G-200 gel column was used to separate and purify the pure polysaccharide POP,and its structural characteristics and antioxidant activity were explored,which provided an effective reference for further development and utilization of Portulaca.The experimental raw material selected in this study was fresh Portulaca oleracea L.Through single factor and orthogonal experiments,the process conditions for extracting crude polysaccharide from Portulaca oleracea L at 4℃ were optimized,and the optimal extraction conditions were determined as:material-liquid ratio 1:30(G/mL),extraction time:13 h,extraction times:3,alcohol concentration:80%.Under these conditions,the yield of crude polysaccharide from Portulaca oleracea L was 6.76±0.19%.Crude polysaccharide extracted from Portulaca oleracea L at 4℃,using Sevag reagent to remove protein in crude sugar,AB-8 macroporous resin to remove pigments,dialysis bag to remove small molecular impurities,and Sephadex G-200 gel column to obtain The yield of purslane polysaccharide POP is 1.86 ± 0.14%,the sugar content is 95.86±0.21%,and the uronic acid content is 30.70±0.16%,indicating that POP is an acidic polysaccharide.Verification by UV spectrum and high performance liquid chromatography showed that POP was a homogeneous polysaccharide with a molecular weight of 2.17×106 Da.POP are mainly composed of six monosaccharides such as rhamnose,arabinose,galactose,glucose,glucuronic acid,and galacturonic acid by ion chromatography,infrared spectroscopy,methylation,nuclear magnetic resonance,periodic acid oxidation,and Smith degradation analysis.Composition,and the molar ratio was 1:1.780:3.619:0.265:1.365:0.414.Existing connection methods are(1→6)linked galactose,(1→3,6)linked galactose,(1→5)linked arabinose,(1→6)linked glucose,and(1→2)Linked rhamnose and T-terminal arabinose.Congo red and circular dichroism experiments found that the POP contains three spiral structures.Scanning electron microscopy results show that POPs have a thin,porous layered structure and are loosely intertwined.DSC and TGA results show that POP has better thermal stability.In vitro antioxidant activity experiments show that POP has certain scavenging ability to DPPH free radicals,hydroxyl free radicals,superoxide anion free radicals and ABTS free radicals,and POP has the strongest scavenging ability to ABTS free radicals,when the POP concentration reaches 3.0 mg/mL,the ability to scavenge ABTS free radicals is as high as 92.26±0.12%,which is equivalent to Vc.