Antimicrobial Activity of Extracts and Fractions of Ginkgo hiloha Leaves, Seed and Outer Seedcoat

摘要

This study was conducted to investigate the antimicrobial activity of Ginkgo biloba L. leaves, seed and outer seedcoat against bacteria. Antimicrobial effects of Ginkgo bihba L. leaves (GBL), seed (GBS) and outer seedcoat (GBO) were examined by paperdisc method and optical density method to determine minimum inhibition concentration (MIC), and observed by scanning electron microscope (SEM) to figure out the morphological change on the surface when Ginkgo biloba leaves extract was treated. The extracts of GBL, GBS and GBO were extracted by solvents such as methanol, ethanol, water. The methanol extract of GBL and GBO showed the highest antimicrobial activity against Bacillus cereus, Bacillus subtilis, Klebsiella pneumoniae, Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus, Yersinia enterocolitica except Escherichia coli and thus was further fractionated. The MICs of the chloroform fraction of GBL methanol extract were 125 iig/mL against B. subtilis, and L. monocytogenes', GBO methanol extract were 62.5 iig/mL against B. cereus and 125 iigiL against B. subtilis, and L. monocytogenes. The microorganisms were treated with chloroform extracts (2000 lig/mL) of GBL and GBO methanol extracts. It was observed by scanning electron microscope (SEM). The cells were expanded and a part of cell wall was completely destructed by GBL and GBO. Thus Ginkgo biloba L. leaves and outer seedcoat could be further developed into a natural antimicrobial agent.