| Eucommia ulmoides has been a Chinese plant with homology of medicine and food since ancient times.In recent years,the physiological activities of plant polysaccharides have attracted more and more attention.In order to develop a new type of antioxidant functional polysaccharides with homology of medicine and food,this paper extracted polysaccharides from Eucommia ulmoides leaves,optimized the extraction process of polysaccharides,explored the physicochemical properties and antioxidant capacity of polysaccharides from Eucommia ulmoides in order to explore the potential value of polysaccharides.1.Extraction process optimization of polysaccharides from Eucommia ulmoidesBy comparing the extraction rate of Eucommia ulmoides polysaccharide under different methods,ultrasonic assisted hot extraction method was selected as the extraction method for the subsequent process optimization.Single factor analysis and Box-Behnken response surface test were carried out for the extraction of Eucommia ulmoides polysaccharide with extraction temperature,extraction time and liquid-solid ratio as variables.The results showed as follows:(1)The content of polysaccharides from Eucommia ulmoides by ultrasonic-assisted hot extraction and enzymolysis was relatively higher(1.97% and 1.88%,respectively),which was significantly higher than that from hot water extraction(P<0.05),but there was no significant difference between the two methods.(2)The optimal extraction parameters of Eucommia polysaccharides were as follows: the liquid-solid ratio was 22:1m L/g,the extraction temperature was 63℃,and the extraction time was 1 h.Under these conditions,the extraction yield of Eucommia polysaccharides could reach 2.60%.2.Physicochemical properties of polysaccharides from Eucommia ulmoidesThe monosaccharide composition,particle size,molecular weight and other physical and chemical properties of Eucommia ulmoides polysaccharide were determined to study its physical and chemical properties:(1)The content of uronic acid in Eucommia ulmoides polysaccharide is 13.8%,which is mainly a heteropoly sugar composed of galactose,glucose,arabinose,rhamnose,galacturonic acid,mannose,glucuronic acid,xylose,ribose and fucose.(2)The particle size of Eucommia ulmoides polysaccharide was 140.18±9.75 nm,and the particle size was relatively uniform.(3)The molecular weight of Eucommia polysaccharides was 101.324 k Da.(4)Polysaccharides from Eucommia ulmoides contain no monosaccharides,phenolic hydroxyl,no protein,is a kind of non-starch polysaccharide.3.Determination of antioxidant capacity of Eucommia ulmoides polysaccharide in vitroThe ABTS+ free radical scavenging ability,DPPH free radical scavenging ability,hydroxyl free radical scavenging ability and total reducing power of Eucommia ulmoides polysaccharide were determined.The results showed that:(1)When the concentration of Eucommia ulmoides polysaccharide was 0.5 mg/m L,the ABTS+ free radical scavenging rate reached 101.17%,and the IC50 was 0.254 mg/m L.(2)When the concentration of polysaccharides was 1 mg/m L,the DPPH free radical scavenging rate reached 87.05%,the IC50 was 0.210 mg/m L.(3)When the concentration of polysaccharides was 30 mg/m L,the scavenging rate of ·OH radical reached 65.92%,and its IC50 was 24.832 mg/m L.(4)When the concentration of polysaccharides was 1 mg/m L,the reducing power was 1.044.In conclusion,polysaccharides from Eucommia ulmoides have strong antioxidant capacity in vitro,and the antioxidant capacity increases with the increase of concentration.4.Relieving effect of polysaccharides on oxidative stress of Eucommia ulmoidesFifty 4-week-old Kunming mice(20.95±1.71 g)were selected to establish the oxidative stress model.The mice were randomly divided into 5 groups with 10 mice in each group.The blank group(group C),Dicaokuai group(group D),low-dose Eucommia ulmoides polysaccharide group(group L),medium-dose Eucommia ulmoides polysaccharide group(group M)and high-dose Eucommia ulmoides polysaccharide group(group H)were set.Mice in L,M and H groups were given 100 mg/kg,200 mg/kg and 400 mg/kg Eucommia ulmoides polysaccharide solution,respectively,and mice in C and D groups were given the same volume of normal saline every day for 14 days.12 h after the last intragastric administration,mice in groups L,M,H and D were intraperitoneally injected with 25 mg/kg diachalquat.The expression levels of antioxidant indexes and related genes in serum,liver and kidney were determined.The morphology of liver tissue and the changes of intestinal microecology were analyzed.The results showed as follows:(1)Compared with group D,the levels of SOD,CAT,GSH-Px and T-AOC in serum of mice in Eucommia ulmoides polysaccharide group(groups L,M and H)were significantly increased,while the levels of MDA were decreased(P<0.05).(3)Eucommia ulmoides polysaccharide up-regulated Nrf2,HO-1,NQO1 gene expression in liver and kidney,and down-regulated Keap1 gene expression in liver and kidney.(4)Polysaccharides from Eucommia ulmoides could increase the ratio of firmicutes to Bacteroidetes in intestinal tract,thus regulating the proportion of intestinal flora. |
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