Isolation,Purification,Structure Characterization And Activity Of Natural Selenium Polysaccharide From Rosa Laevigata Michx.

Rosa laevigata Michx.is a plant of the genus Rosaceae.Rosa laevigata Michx.has a long history of being used as medicine,and there are many records in Chinese medical books of the past dynasties.Rosa laevigata Michx.is rich in resources and widely distributed in China.The content of polysaccharide is high,which is an important active ingredient of Rosa laevigata Michx..The extraction,purification,structure characterization and activity of polysaccharides from Rosa laevigata Michx.fruit.Were studied in this paper.The main contents are as follows:The crude polysaccharides from the Rosa laevigata Michx.fruit were extracted by hot water method.The crude polysaccharides were decolorized and purified by macroporous resin,anion exchange column and gel chromatography column.Three natural selenium polysaccharides（Se-RLFP-1,Se-RLFP-2 and Se-RLFP-3）were obtained.The selenium content of the above-mentioned selenium polysaccharides was determined by atomic fluorescence spectrometry to be 19.72 ng/mL,16.49 ng/mL and 21.6 ng/mL,respectively.The relative molecular weights of the above-metioned selenium polysaccharides were determined by high performance gel permeation chromatography to be 31 KDa,24 KDa and 16 KDa,respectively.High performance liquid chromatography（HPLC）was used to identify the monosaccharide composition of the above-metioned selenium polysaccharides,the results showed that Se-RLFP-1 was composed of rhamnose,xylose,mannose and glucose with a molar ratio of 0.13:0.49:0.05:0.34;Se-RLFP-2 was composed of rhamnose,xylose and glucose with a molar ratio of 0.12:0.51:0.39;and Se-RLFP-3 was composed of rhamnose,xylose and glucose with a molar ratio of0.39:0.44:0.17;The above-mentioned selenium polysaccharides undergo periodate acid oxidation-Smith degradation,and results showed that Se-RLFP-1,Se-RLFP-2 and Se-RLFP-3 were composed of 1→6,1→4,1→3,1→2 glycosidic bonds in a ratio of0.02:0.03:0.85:0.07;0.01:0.13:0.84:0.01 and 0.09:0.15:0.65:0.02,respectively.According to the ¹H-NMR,¹³C-NMR,¹H-¹H-COSY,HSQC and HMBC nuclear magnetic resonance spectra of Se-RLFP-1,Se-RLFP-2 and Se-RLFP-3,the above selenium polysaccharides were furan configurations,and Se-RLFP-1 contained→3)-β-L-Rhap-（1→4）-α-D-Glcp-（1→and other structural fragments;Se-RLFP-2contained→3）-β-L-Rhap-（1→4）-β-D-Xylp-（1→and other structural fragments;Se-RLFP-3 contained→3）-α-D-Galp-（1→4）-α-D-Galp-(1→and other structural fragments.Scanning electron microscopy（SEM）and thermogravimetric analysis（TGA）were used to characterize the surface morphology and thermal stability of selenium polysaccharides.The test results showed that as the relative molecular weight of selenium polysaccharides increases,the gaps between the surface structures become tighter,more continuous and complete,and the thermal stability gradually increases,but the difference was not obvious.In this paper,the antioxidant activities of three natural selenium polysaccharides were tested.The results showed that Se-RLFP-1,Se-RLFP-2 and Se-RLFP-3 had scavenging effects on DPPH and ABTS free radicals.The experimental results of the neuroprotective activity of the above-mentioned selenium polysaccharides show that when the concentration reaches 100μg/mL,Se-RLFP-1,Se-RLFP-2 and Se-RLFP-3 all had better neuroprotective activity;In addition,Se-RLFP-2 had a significant increase in the SOD activity in SH-SY5Y cells induced by H₂O₂ and a significant decrease in MDA content.It showed that Se-RLFP-2 had a protective effect on the oxidative stress damage of SH-SY5Y cells induced by H₂O₂.