Evaluation Of The Properties Of Polysaccharide Degradation Products From Sea Buckthorn Pomace And Its Anti Diabetic Activity

Sea buckthorn（Hippophae rhamnoides L.）pomace is the main by-product of Sea buckthorn processing.The polysaccharide content is rich in 9-15%of the pomace,and it has various pharmacological activities such as anti-oxidation,hypoglycemic,and hypolipidemic.However,the high molecular weight and poor water solubility of Sea buckthorn polysaccharides lead to its low utilization rate.In this study,the H₂O₂-Fe²⁺system was used to prepare sea buckthorn degradable polysaccharides and to separate and purify them.By measuring the physical and chemical properties and structural characterization of Sea buckthorn polysaccharides before and after degradation,the effect of degradation treatment on the antioxidant capacity and hypoglycemic and lipid-lowering activities of Sea buckthorn polysaccharides was studied.In this study,the highly efficient and environmentally friendly H₂O₂-Fe²⁺method was applied to degrade polysaccharides from Sea buckthorn pomace,which provided a basis for further improving the application value of polysaccharides from Sea buckthorn pomace.The specific results of the research are as follows:（1）Preparation,separation and purification of polysaccharide degradation products of Sea buckthorn pomace.Six degraded polysaccharides from Sea buckthorn were prepared by different degradation methods(H₂O₂-Fe²⁺、H₂O₂-V_C).The relative content of reducing sugar,DPPH free radical scavenging ability,α-glucosidase inhibitory ability and sodium glycocholate binding ability were used as indicators to determine the appropriate degradation method.The DPPH radical scavenging ability of 1.0 mol/L H₂O₂-Fe²⁺system for polysaccharide degradation andα-glucosidase inhibitory ability was the strongest.The 2.0 mol/L H₂O₂-Fe²⁺system had the highest relative reducing sugar content and the strongest bile salt binding ability in degrading polysaccharides,but there was no significant difference compared with the 1.0 mol/L H₂O₂-Fe²⁺system（P>0.05）.Considering comprehensively,it is determined to use 1.0 mol/L H₂O₂-Fe²⁺system to prepare Sea buckthorn degraded polysaccharides.The crude polysaccharide of Sea buckthorn and the degraded polysaccharide of Sea buckthorn prepared by H₂O₂-Fe²⁺degradation system was separated and purified by DEAE-52 cellulose resin to obtain SBP and SBDP.（2）Physicochemical properties and structural characterization of polysaccharide degradation products of sea buckthorn pomace.The molecular weight of SBDP（2.902×10⁴ Da）is significantly lower than that of SBP（3.016×10⁵ Da）.The monosaccharide composition of SBP and SBDP was the same,and the molar ratio changed obviously.SBP was dominated by galacturonic acid,and SBDP was dominated by arabinose and mannose.Infrared and nuclear magnetic resonance spectra showed that SBDP and SBP had similar configurations,functional groups and glycoside chains.This indicated that H₂O₂-Fe²⁺degradation did not destroy the structural characteristics of Sea buckthorn polysaccharides.H₂O₂-Fe²⁺treatment reduced the particle size of sea buckthorn polysaccharides,improved the solubility of sea buckthorn polysaccharides,and SBDP had better hygroscopicity and moisture retention.Both polysaccharides showed shear-thinning properties and Newtonian fluid behavior,and the apparent viscosity of SBDP was always lower than that of SBP,and had better gel performance and system stability.（3）Research on hypoglycemic,lipid-lowering and antioxidant capacity of polysaccharide degradation products of sea buckthorn pomace.The in vitro antioxidant capacity of SBDP was significantly improved（P<0.05）.The scavenging rates of DPPH radical,ABTS⁺radical and hydroxyl radical increased by 18.06%,2.91%and 7.36%respectively at the concentration of 2mg/ml.When the concentration was 6 mg/mL,the superoxide anion O^2-radical scavenging rate increased by 27.06%.The half-inhibitory concentration(IC₅₀ value)of SBDP onα-glucosidase andα-amylase decreased by 0.114 mg/mL and 0.471 mg/mL,respectively.At concentration of 2mg/mL,the inhibition rate of SBDP on pancreatic lipase was 41.47%,and the binding ability to sodium glycocholate and sodium taurocholate was significantly improved（P<0.05）.（4）Anti-diabetic effect of polysaccharide degradation products of Sea buckthorn pomace on diabetic mice.The anti-diabetic activity of SBDP was studied by establishing a diabetic mouse model induced by alloxan.The results showed that compared with the diabetic group（DG）,SBDP could significantly reduce the weight of mice（P<0.05）,improve the symptoms of eating and drinking more in diabetic mice,and protect the liver,kidney and pancreas.50 mg/kg SBDP has obvious hypoglycemic effect,can significantly improve the glucose tolerance of diabetic mice（P<0.05）,reduce the level of glycosylated serum protein,increase insulin secretion,and improve the level of liver glycogen in diabetic mice.The levels of total cholesterol（T-Cho）and low density lipoprotein cholesterol（LDL-C）in serum of diabetic mice fed SBDP were significantly decreased（P<0.05）,the levels of total triglyceride（TG）and high density lipoprotein cholesterol（HDL-C）were significantly increased（P<0.05）,and the levels of aspartate aminotransferase（AST）and alanine aminotransferase（ALT）were significantly decreased（P<0.05）.SBDP could significantly increase the levels of catalase（CAT）,superoxide dismutase（SOD）and glutathione peroxidase（GSH-PX）in the liver of diabetic mice（P<0.05）,reduce the level of malondialdehyde（MDA）,and reduce the liver tissue damage of diabetic mice.In conclusion,this study showed that H₂O₂-Fe²⁺degradation treatment could significantly improve the hypoglycemic and lipid-lowering activities and antioxidant capacity of Polysaccharides from Sea buckthorn pomace,which could provide reference for the application of Polysaccharides from Sea buckthorn pomace in special foods and antidiabetic drugs.