| Bamboo shoot is the newborn bud of bamboo which is a perennial evergreen herb belonging to Bambusoideae.It is the delicious,nutritious and traditional forest vegetable.Bamboo shoot shell,also known as bamboo sheath,is the main processing by-products of bamboo shoots.It is the waste of resources and the pollution to the environment for discarding the bamboo shoot shells.In this thesis,bamboo shoot shells from Fujian Province were chosen as the research materials,the extraction,purification,structure,antioxidant and hypoglycemic effects of the polysaccharides from bamboo shoot shell were studied.The results could provide the theoretical basis for the comprehensive utilization of bamboo shoot by-products and the development of functional food.(1)Taking bamboo shoot shells from Fujian as raw materials,3 kinds of extraction processes including hot water extraction,microwave assisted extraction and microwave-ultrasonic assisted extraction were studied by orthogonal test.The results were summarized as follows.①The optimal conditions of hot water extraction were determined with 1:30(g/mL)as the solid to liquid ratio,80℃ of extraction temperature,2 h of extraction time,and 3 times of extraction,resulting in the 1.52%of extraction rate of bamboo shell polysaccharides.②The optimal conditions of microwave assisted extraction process were obtained with 3 min microwave,1:45(g/mL)of the solid to liquid ratio,800 W of the microwave power and 4 times extraction,leading to 1.41%of extraction rate of bamboo shoot shell polysaccharides.③The best conditions of microwave-ultrasound assisted extraction were 30 min extraction time,1:25(g/mL)of solid to liquid ratio,200 W of the microwave power,750 W of ultrasonic power and 3 times extraction,and the extraction rate of bamboo shoot shell polysaccharides reached 2.76%.Ultrasonic-microwave assisted extraction can significantly improve the extraction rate and save time as well.(2)Proteins were removed from bamboo shoot shell polysaccharides by lead acetate method.Proteins removal rate was 80.17%and polysaccharide retention rate was 81.12%.After deproteinization,the macroporous adsorptive resin NKA-II was selected for decolorization of bamboo shoot shell polysaccharides.The optimum conditions of static decolorization were determined:1 mg/mL of polysaccharide solution,original solution pH value,3.0 h of decolorization time,temperature 25℃,0.20 g/mL of adding amount of macroporous adsorption resin NKA-II.The decolorization rate was 82.31%and polysaccharide retention rate was 82.19%.After deproteinization and decolorization,the solution of bamboo shoot shell polysaccharides was concentrated and dialyzed.The purified polysaccharide named BSP was obtained after freeze drying.(3)BSP solution was purified by a DEAE-52 cellulose anion-exchange chromatography column and a gel-permeation chromatography on a column of Sephadex G-200,then one of the acidic polysaccharide fractions named BSP2a was collected.BSP2a was identified as homogeneous components by HPGPC-MALLS with the PDI(Mw/Mn)of 1.389,the Mw of 1.629×104 kDa and the Rw of 306.7nm.The UV spectrum analysis showed that BSP2a did not contain nucleic acid and protein.The IR spectral analysis indicated BSP2a was a pyran polysaccharide containing a small amount of glycoprotein with a branched structure.The SEM and AFM electron microscope showed that the intermolecular force of BSP2a was very strong,forming a network structure with diameter in the range of 250-500 nm with 5μg/mL of aqueous solution,and the sugar chains’ height was about 0.25-1.5 nm.The HPLC revealed that BSP2a was composed of rhamnose,arabinose,xylsoe and fructose.(4)Compared to Vc,antioxidant activities of CBSP and BSP were studied in vitro,including scavenging superoxide anion,scavenging hydroxyl free radical and scavenging 1,1-Diphenyl-2-picrylhydrazyl(DPPH).The results showed that bamboo shoot polysaccharides had certain antioxidant capacity which increased with the increase of polysaccharides concentration.The scavenging capacity of DPPH was similar to Vc,while the anti-hydroxyl free radical ability was stronger than Vc.It was observed that the IC50 of CBSP and BSP were 0.11 mg/mL and 0.22 mg/mL,respectively,and both of them were better than that of Vc.(5)Taken hypoglycemic drugs metformin as the control,the hypoglycemic effects of CBSP on the mice model of type Ⅱ diabetic,induced by streptozotocin(STZ)and a high-fat diet,were studied.The indexes including body weight,fasting blood glucose,glucose tolerance and the area under,triglyceride and total cholesterol,serum insulin were tested during 21 days.Results showed that blood glucose and blood lipid levels of type Ⅱ diabetic mice were significantly ameliorated by administration of CBSP.Especially,fasting blood glucose of high-dose group mice decreased to 6.3 mmol/L,serum insulin levels were 10.85 mIU/L higher than the model group’s,TG and TC were 34.8%and 26.5%lower than the model group,respectively.Those effects were similar to the drug treated group,indicating that CBSP has potential auxiliary hypoglycemic effect. |
