寒地桑叶多糖的提取纯化、结构表征及其生物活性OA

To investigate the structural characteristics and functional activity of mulberry leaf polysaccharide(MLP)from Morus abla L.cv.Longsang 1,DEAE-52 cellulose column and Sephadex G-100 gel chromatographies were used to purify and separate MLP into three fractions,named MLP-1,MLP-2,and MLP-3.The structural properties as well as the in vitro antioxidant,hypoglycemic,and lipid-lowering activities of the purified polysaccharides were analyzed.The results showed that the yields of MLP-1,MLP-2,and MLP-3 were 12.75%,5.52%,and 2.63%,respectively.Compositional analysis showed that the total sugar content of MLP-1,MLP-2,and MLP-3 decreased in that order,while the contents of uronic acid,protein,and polyphenol exhibited the opposite trend.Gel permeation chromatography(GPC)revealed that MLP-1 and MLP-3 were homogeneous polysaccharides with molecular masses of 625.69 and 7.25 kDa,respectively,whereas MLP-2 was a mixture of polysaccharides with molecular masses of 769.05 and 41.35 kDa.Monosaccharide composition analysis showed that the three polysaccharides were composed of fructose,mannose,glucose,and galactose at different molar ratios.Fourier transform infrared spectroscopy(FT-IR),iodine-potassium iodide assay and atomic force microscopy(AFM)indicated that all three polysaccharide components were pyranoses,characterized by long side chains and multiple branches interwoven with each other.Congo red staining showed that MLP-1 and MLP-2 possessed a triple helix structure,while MLP-3 did not.Physicochemical analyses indicated that MLP-1 significantly outperformed the other polysaccharide components in terms of water-holding and water-retention capacities,while MLP-2 performed the best in terms of water solubility and water-absorbing capacity.In terms of swelling capacity and oil-holding capacity,MLP-3 performed the best.Rheological analysis indicated that MLP-1 and MLP-2 exhibited superior apparent viscosity and solid elastic properties.Moreover,MLP-1 was more prone to phase transition at low temperatures.The free radical scavenging capacities of the polysaccharides decreased in the order:MLP-1>MLP>MLP-2>MLP-3,the inhibitory activity against α-glucosidase,α-amylase,and pancreatic lipase in the order:MLP-1>MLP-2>MLP3,the bile salt binding capacity in the order:MLP-1>MLP-3>MLP-2,and the cholesterol adsorption capacity in the order:MLP-3>MLP-2>MLP-1.The results of this study can provide experimental data for the application and functional evaluation of mulberry leaves in cold regions.