| This paper mainly studied the functions of water extract from Vaccinium bracteatum Tbunb. leaves(VBTL). Animal experiment was used to study the effect of the water extract on STZ-induced diabetic mice. Animal experiments results showed that water extract from VBTL can improve the condition of diabetic mice. After 4 weeks, the body weights of diabetic mice treated with water extract from VBTL were increased 61%, the blood glucose levels were reduced 14.18%, insulin level significantly increased. Water extract from VBTL possess a potential hypolipidemic effect in diabetic mice, but have no effect on organ.The antibacterial effect and the minimal inhibitory concentration (MIC) of water extract from VBTL were determined by the cylinder plate method and two-fold dilution method. The antibacterial experiment results showed that water extract from VBTL had obvious inhibition effects on bacteria, but had no obvious inhibition effects on mold and yeast. The MIC experiment results showed that the MIC to Staphylococcus aureus was 7.65 mg/mL, the MIC to Escherichia coli and Bacillus subtilis were 15.30 mg/mL.After analysising the component of water extract from VBTL, we speculate that the effective element of antibacterial effect was flavonoids, and the effective element of the effect on STZ-induced diabetic mice was polysaccharides.We used Box-Benhnken central group experiment and response surface analysis to obtain the optimum conditions for the extract technique of water-soluble flavonoids. The results showed that the optimum conditions were: extraction temperature 50℃, extraction time 2h, ratio of water to material 40 and extract twice. In these conditions, the yield of water-soluble flavonoids from VBTL was 16.82mg/g.The antibacterial effect and the MIC of water-soluble flavonoids from VBTL was determined by the cylinder plate method and two-fold dilution method. The antibacterial experiment results showed that water extract of VBTL leaves had obvious inhibition effects on bacteria, but had no obvious inhibition effects on mold and yeast. The MIC experiment results showed that the MIC to Staphylococcus aureus was 1.03 mg/mL, the MIC to Escherichia coli was 2.06 mg/mL, and the MIC to Bacillus subtilis was 4.12 mg/mL. The antibacterial experiment results showed that the antibacterial effect of water-soluble flavonoids is better than potassium sorbate and sodium benzoate.Some other factors which influenced the antibacterial effect of water-soluble flavonoids from VBTL and the mechanism of antibacterial were preliminarily studied. The result showed that addition of glucose or NaCl can improve the antibacterial activity of water-soluble flavonoids from VBTL. The time-kill result showed that at 3×MIC and 5×MIC concentrations, the growth of Escherichia coli and Bacillus subtilis were completely wiped out within 12h, at 1×MIC and 3×MIC concentrations, the growth of Staphylococcus aureus were completely wiped out within 12h. At 5×MIC concentrations, the growth of Staphylococcus aureus were completely wiped out within 7h. The result of mechanism showed that flavonoids changed the permeability of the cell membrane, in this way the growth of bacterial was restrained.We used Box-Benhnken central group experiment and response surface analysis to obtain the optimum extraction conditions for water-soluble sugars from VBTL. The results showed that the optimum conditions were: extraction temperature 65℃, extraction time 2.5h, pH value of solution 9.5, solid to liquid ratio 1:45, the yield of water-soluble sugars from VBTL was 89.80mg/g. Then single factor experiments were used to determine the optimum conditions for ethanol precipitated water-soluble polysaccharides from VBTL. The optimum conditions were: the ratio of extract volume and ethanol volume 1:5, ethanol concentration 90%, standing time 6h, and ethanol precipitated twice. In these conditions, the yield of water-soluble polysaccharides was 36.55mg/mL.Four kinds of macroporous resins were screened to decolorize. After comparing macroporous resin AB-8 was chose to decolorize. According to the results optimum static adsorption conditions for AB-8 were: resin content 8%, pH value of solution 2, temperature 35℃, and reaction time 18h. In these conditions, polysaccharide retention rate was 82.03%, the decolorization rate was 88.11% and protein removal rate was 78.35%. Finally, DEAE-Sepharose FF column was used for further purification, the results showed that two polysaccharide components were isolated from water-soluble polysaccharides .
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