Structure Analysis,Antibacterial Activity And Application Research Of Polysaccharides From Gynostemma Pentaphyllum

Gynostemma pentaphyllum Makino as research object, the extraction, isolation and purification, structural characterization, antioxidant activity, antimicrobial activity and the preparation of polysaccharide-iron complex of the polysaccharides from Gynostemma.pentaphyllum were studied in this thesis. The main research contents and results are as follows:The Gynostemma.pentahyllum polysaccharides (GP) was extracted by enzyme hydrolysis method. The orthogonal experiment were applied to optimize the extraction process with enzyme dosage, pH, enzymolysis time and temperature as factors, and the optimal conditions for the extraction of GP were determined:enzyme dosage2%, pH6.0, enzymolysis time2.5h, enzymolysis temperature45℃. Under this optimized extraction process, the yield of GP was2.46%.Four deproteinization methods were compared and found that the D301Weak Alkaline Big-aperture Resin performed better than other methods in terms of the protein removal efficiency. The optimal technological conditions for the resin adsorption process were obtained by using the response surface analysis. The optimal conditions were as follows:original extract concentration of2mg/mL, pH6.0, sample volume of160mL, and flow velocity of3mL/min. Three polysaccharide components were separated by Sephadex G-200column chromatography graded purification. Monosaccharide composition analysis of the GPI was carried out by HPLC, which indicated that the GPI consisted of mannose, rhamnose, galacturonic acid, glucose, galactose, xylose, arabinose. The results of IR Spectrum and nuclear magnetic resonance (NMR) suggested the presence of furan structure in the G. pentahyllum polysaccharides.The anti-lipid peroxidation, DPPH radical scavenging, hydroxyl radical scavenging and superoxide anion scavenging activities of Vc, the original GP extracts and the three purified polysaccharide components were studied to confirmed the antioxidant activity of the GP. The results demonstrated that the GP showed a strong antioxidant activity. Antibacterial effect of the GP was studied by measuring the diameter of inhibition zone. The polysaccharides had an obvious inhibitory effect on bacteria, but had no effect on fungi.The preparation technology of polysaccharide-iron complex was optimized by using the orthogonal experiment. The optimal complexation conditions were determined as the mass ratio of FeCl3and GP is1:1, pH8.0, reaction time of1.5h and temperature of80℃. Ultraviolet spectrum and infrared spectrum analysis indicated that the absorption peak of the hydroxyl in this complex had an obvious change, which illustrated that Fe3+mainly combined with hydroxyl of the GP to form a stable complex.