LI Lu1, HU Huanhuan1,2, ZHANG Huafeng1*, YANG Shanhui1, QIAO Chunlei1, HAO Miao1
(1 Key Laboratory of Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resources Development of Endangered Crude Drugs in Northwest China, School of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi′an 710119, Shaanxi, China;2 Zhejiang Guojing Pharmaceutical Co. Ltd., Longquan 323700, Zhejiang, China)
Abstract:
The antibacterial activity of alkaloids from Epimedium was studied using Escherichia coli as a model microorganism. The minimum inhibitory concentration of Epimedium alkaloids against E. coli was determined by a broth dilution method. And the inhibition zone diameter was measured by an Oxford cup method. In order to identify antibacterial mechanism of Epimedium alkaloids, effects of alkaloids on soluble protein, nucleic acid, metallic ions, electrical conductivity and cell ultrastructure were investigated systematically.Epimedium alkaloids exhibited relatively high inhibitory activity against E. coli mainly during exponential growth phase, and the minimum inhibitory concentration of alkaloids was determined to be 60 mg/mL.After E. coli was treated with Epimedium alkaloids, the contents of extracellular and intracellular soluble protein were found to increase remarkably. Relative contents of K+, Mg2+ and nucleic acid outside cells of E. coli also increased significantly. And electrical conductivity of E. coli broth changed markedly. Some cavities and hollows took place on cell surface, which indicated that cell surface was seriously destroyed. In summary, antibacterial activity of Epimedium alkaloids against E. coli was most probably related to destructive effects on cell structures.
KeyWords:
Epimedium; alkaloid; Escherichia coli; antibacterial mechanism
