Study On The Extraction, Purification And Vitro Antioxidants Activity Of Polysaccharides From Bambusa Textilis Var. Persistens. Leaves

Bamboo, a grass (Poaceae) Bambusoideae (Bambuaoideae) perennial evergreen grass, has the ornamental value and applied value all over the world. China is rich in bamboo class resources and enjoyed the reputation of the bamboo kingdom. Bamboo plants are regarded as the essential component of forest resources.Polysaccharide from bamboo leaves is a significant kind of plant polysaccharide, which has various health care functions. However, researches were mainly focused on flavononids and its biological activity as well as pharmacological function. The research reports on bamboo leaves polysaccharide were much less than those of flavononid.Bambusa textilis var. Persistens, the peculiar bamboo found in Changsha Hunan, is one of the Bambusa variations. In this thesis, the author focused on the extraction, purification, physical and chemical properties and vitro antioxidant activity of polysaccharide from this peculiar bamboo leaves.The research results can be sumerized as the following aspects:1. Content determination of polysaccharide from different kinds of bamboo leaves, establishment of the extraction kinetics modesThrough phenol-sulfuric acid method, polysaccharide content of bamboo leaves from Bambusa textilis var. Persistens, Phyllostachys pubescens, Neosinocalamus affinis, Phyllostachys heteroclada, Phyllostachys kwangsiensis and Phyllostachys bambussoides were22.10、23.68、16.05、21.74、24.83、24.30mg/g, respectively. The effects of polysaccharide extraction for the temperature, time and solid-liquid ratio were investigated by single factor experiment, and the fitting equations on various factors were acquired by established kinetic models.2. Separation and purification of polysaccharideSevag method, trichloroacetic acid method and polyamide adsorption method were used to remove protein from PBL, the results showed that the deproteination rate for polyamide adsorption method is the highest among these ways and up to57.77%, the loss rate of polysaccharide for it is between the other ways,30.86%. The removed protein polysaccharide (PBL-0) was applied to DEAE-52cellulose column chromatography, then the column was stepwise eluted with0,0.1,0.3,0.5M NaCl solutions, and four fractions of polysaccharides (PBL-H2O, PBL-1, PBL-2, PBL-3) were obtained. The four purified fractions were concentrated, dialyzed and lyophilized, and PBL-NaCl is amalgamated by PBL-1, PBL-2, and PBL-3.3. Physical and chemical properties of polysaccharideSolubility test:PBL-H2O and PBL-NaCl are easily soluble in distilled water, PBL in hot water; all are not soluble in organic solvents. The molecular weights (Mw) of PBL-H2O and PBL-NaCl, determined by high performance gel-filtration chromatography (HPGPC), were24110.6Da and22942.8Da, respectively. Analysis of the PBL-H2O and PBL-NaCl monosaccharide composition and molar fraction by high performance liquid chromatography (HPLC) indicated that both of them were mainly composed arabinose, galactose, glucose and xylose; meanwhile, HPLC also was applied in water elution and NaCl elution polysaccharide from Moso Bamboo leaves, namely PML-H2O and PML-NaCl, and the result was shown that the absolute proportion in both was occupied by glucose. Preliminary PBL, PBL-H2O and PBL-NaCl characterization were conducted by FT-IR and the consequence indicated that protein absorption peaks were contained in PBL, β-pyranoside of sugar residues configuration was existed within all. UV scanning spectrum further illustrates protein is contained in PBL, nucleic acids is not found in all of sample polysaccharides.4. Vitro antioxidant activities of polysaccharideCompared the scavenging ability of DPPH, ABTS free radical in vitro about PBL-H2O, PBL-NaCl, PBL, PML, FML (Flavone from Moso bamboo leaves) and TP (Tea polysaccharide), the results exhibited antioxidant activities in a concentration-dependent manner. Both of free radical evaluation systems showed the strongest and lowest antioxidant capacity was TP and PBL-H2O, respectively; the rest of sample on antioxidant capacity were between them. Antioxidant capacity of PBL was less than that of PML. The antioxidant capacities of PBL-H2O and PBL-NaCl were lower than that of PBL, and some compositions that have a synergistic antioxidant for polysaccharide were washed during the purification process, presumably.