Structural Characterization Of Polysaccharides From Portulaca Oleracea L.and Its Study On Repairing Pb-induced Learning And Memory Deficit

As a traditional edible/medicinal herb with great nutritional value and bioactivity,Portulaca oleracea L.has been favored by more and more people.Today,the impact of environmental pollution on health has aroused people's concern.As a pervasive environmental toxic metal,Lead(Pb)negatively affects cognition and memory processes and the mechanisms of which may involve with oxidative stress.Portulaca oleracea L.polysaccharides were obtained from Portulaca oleracea L.plant and have extensive actions in pharmacology such as antioxidant activity.However,it still remains unclear that whether Portulaca oleracea L.polysaccharides could improve the learning and memory damage induced by Pb exposure.To solve the problem above,we conducted some research and got the following results:1.Structural characterization of polysaccharides from Portulaca oleracea L.Portulaca oleracea L.polysaccharides(POP)was obtained from Portulaca oleracea L.by hot water extraction,ethanol precipitation,decoloration,deproteinization and dialysis.Then an acidic polysaccharide fraction named POPs was isolated and purified by DEAE-52 column chromatography,which consisted of galactose(50.10%),arabinose(32.51%)and rhamnose(12.79%)and bits of glucose(4.61%).The result of HPLC revealed that POPs was a homogeneous polysaccharide with an average molecular weight of 1.51×107 Da.Methylation analysis,FT-IR spectroscopy and NMR were employed to characterized POPs structure.POPs was composed by ?4)-?-Galp-(1???2)-?-Rhap-(1???3)-?-Galp-(1???-Galp-(1? and T-?-Araf.2.Study on the physiological activity of polysaccharides from Portulaca oleracea L.The physicochemical properties of POPs were investigated by XRD?TG-DSC?AFM?SEM?Zeta-sizer and Rotational rheometer.The results revealed that the zeta potential of POPs was-33.4m V,and it presented as non-Newtonian fluids and was a number of pseudoplastic fluids.Meanwhile,POPs exhibited loose flaky morphology with semi-crystalline structure and has good thermal stability.3.Study on the antioxidant activity of polysaccharides from Portulaca oleracea L.In vitro,POP exhibited scavenging ability of hydroxyl radical,DPPH and ABTS radical in a dose-dependent manner,which showed that POP has good antioxidant activity.Moreover,Treatment with POP markedly increased the survival of PC12 cells and repressed the generation of reactive oxygen species following Pb exposure.4.Study on the effect of polysaccharides from Portulaca oleracea L.on Pb-induced learning and memory deficit in rats.In vivo experiments,Sprague-Dawley(SD)rats exposed to Pb from the mother generation to the offspring.From the second month,the pups treated with POP(POP: crude Portulaca oleracea L.polysaccharide was purified and the sugar content of which was over 70%)by intragastric gavage in dosage of 200?400 and 600 mg/kg·bw lasting for one month.After that,the ability to improve learning and memory of POP was observed using Morris water maze,and the dendritic spine morphology in hippocampus was observed by Golgi-cox staining method.The results showed that the swimming speed had no significant difference between the groups.However,Pb exposure led to an increase in escape latency and a decrease in the time spend in 4th quadrant and the platform crossing times of rats in the probe test,which could be attenuated by POP treatment;POP exerted neuroprotection effect against Pb-induced spines loss in hippocampus neuron in dose-dependent manner.Conclusion,POP has great antioxidant activity and exerts the neuroprotection effect against Pb-induced generation of ROS,spines loss and spatial memory deficits.