| Quercus variabilis Blume(Q. variabilis), a perennial deciduous tree of Fagaceae, its wood, cork, acorn, valonia and leaves have a very important economic and medicinal value. It plays an important role in the development of provincial economy and the protection of ecological environment. Recently, the research on valonia and shell of Q. variabilis is mainly focus on tannin extract, activated carbon and pigment, and there are few studies on the other sides, such as chemical composition, antibacterial activity and mechanism. Therefore, to fully develop and utilize the resources of Q. variabilis, the objective of this study was to analysis the chemical composition, the antibacterial activity of valonia and shell extracts, and to investigate the antibacterial mechanism of VEE and VBF of valonia against the indicator bacteria(Sallmonlla paratyphi A and Staphylococcus saures), and the results was expressed in the follow:1. The analysis of effective constituent of the ethanol extract and its four secondary extracts of valonia and shell from Q. variabilis indicated: the highest level of TPC was found in VWF of valonia, with the content of 711.46±7.32 mg GAE/g; the highest level of TFC was found in SBF of shell with the content of 45.82±0.02 mmol QUE/100g; the highest level of TTC was found in VBF of valonia, with the content of 258.02±3.34 mg TAE/g.2. By RP-HPLC analysis, four compounds(ellagic acid, theophylline, caffeic and tannin acid) were identified from valonia and shell. The content of ellagic acid was found in VEAF of valonia(74.57±3.02 mg/g). Theophylline and caffeic acid was significantly high in VBF of valonia, with the content of 66.23±2.21 mg/g and 5.63±0.57 mg/g. Tannin acid was found in SEAF of shell, with the content of 16.96±1.87 mg/g.3. The antibacterial activity of ethanol extracts of shell and valonia against five bacteria, including Staphylococcus aureus(S. aureus), Salmonella paratyphi A(S. paratyphi A), Salmonella typhimurium(S. typhimurium), Salmonella enteritidis(S. enteritidis) and Listeria momocytogenes(L. momocytogenes) was measured. The results indicated that VEE was sensitive to S. aureus and S. paratyphi A. The inhibition zones of VEE were 12.37±0.36 mm and 10.89±0.12 mm, better than that of Pomegranate peel and ellagic acid. Furthermore, the antibacterial activity of SEE against S. paratyphi A and S. aureus was better than the other microorganism, with the inhibition zones of 9.62±0.16 mm and 8.99±0.22 mm.4. Taking the inhibition zone, minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC) as assessment index, the antibacterial activity of shell and valonia ethanol extract and its four secondary extracts against S. aureus and S. paratyphi A was investigated. The results indicated that VBF and VEE had the strong antibacterial activity. The inhibition zone of VBF and VEE against S. paratyphi A were 15.92±0.44 mm and 12.37±0.36 mm, and both the MIC and MBC were 1.25mg/m L. That of S. aureus was 12.26±0.14 mm and 10.89±0.12 mm,and both the MIC and MBC were 0.625 mg/m L.5. The mechanism of VBF and VEE of valonia from Q. variabilis against S. paratyphi A and S. aureus was preliminarily investigated. The results showed that after the bacteria treated by VBF and VEE, the leakage content of nucleic acid was higher than control, and the high content of cell leakage protein and total sugar in the medium of S. aureus reached 7.51 μg/m L and 166.54 μg/m L. That of S. paratyphi A was 5.79 μg/m L and 86.32 μg/m L, so the samples had a strong impact on the membrane permeability. The determination of the content of phosphorus metabolism showed that the samples had influence on the normal growth and cellular metabolism of bacteria. The SDS-PAGE analysis found that the samples could inhibit cellular protein synthesis. The scanning electron microscope analysis indicated that the samples could change the surface morphological structure of bacteria. The research on mechanism declared VBF and VEE had a stronger inhibition effect on S. aureus. |
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