Study On Antibacterial Active Constituents Of Two Medicinal Plants

Recently, more and more attention has been pad to the study on natural products with antibacterial activity due to fatal clinic infection. Therefore, it is of great significance to research and develop natural antibacterial drugs on clinical infectious diseases. In this thesis, the chemical components from cones of Platycladus orientali (Linn.) Franco and the whole plant of Indigofera bungeana Walp were prepared. And their antibacterial activities were further investigated. It will strengthen the foundation for further development of drugs on clinical infectious diseases.The crude extract and various polar fractions were screened for antibacterial activities by disc-diffusion method. The minimum inhibitory concentrations (MICs) were further determined for active polar fractions by the broth micro-dilution method. The result indicated that the crude extract, petroleum ether, ethyl acetate and n-butanol parts possessed antimicrobial activity. The MICs of petroleum ether soluble-part were all78.2μg/mL against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus, Baicllus licheniformis and Streptococcus agalactiae. The MICs of ethyl acetate extract were156.3-625μg/mL against the six test bacteria. The n-butanol extract have no antimicrobial activity against six bacteria at the concentration of1250μg/mL12compounds were isolated from the active components of the petroleum ether extract from cones of Platycladus orientalis and9compounds were identified by1NMR,13C-NMR and EI-MS. They were respectively trans-communic acid(1), lambertianic acid(2),15-hydroxy-8(17),13-labdadien-16,15-olid-19-oic acid(3), isocupressic acid(4),15-ace-tylisocupressic acid (5),8(17),13-ent-labdadien-15,16-lactone-19-oic acid (6), sandaracopimaric acid (7),6a-hydroxysandaracopimaric acid(8) and8(14),15-isopimaradien-3β,19-diol (9).15-acetylisocupressic acid (5) and6a-hydroxysandaracopimaric acid(8) are isolated from this genus for the first time. The MICs were determined for above compounds by broth micro-dilution method and eight compounds possessed antibacterial activity. The strongest antibacterial activity was seen for compound7against Streptococcus agalactiae, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus with MICs of62.5μg/mL and against Escherichia coli and Bacillus licheniformis with MICs of125μg/mL. It showed bactericidal activity against Klebsiella pneumoniae with MBC of250μg/mL and against the other5microorganisms with MBCs of500-1000μg/mL. Compound2have no antimicrobial activity against six bacteria at the concentration of1000μg/mL. The other compounds showed anti-bacterial activity against six bacteria with MICs of125-1000μg/mL and MBCs of125-1000μg/mL or higher.15compounds were isolated from the petroleum ether soluble-part of acetone extract from the whole plant of Indigofera bungeana Walp and5compounds were identified by1NMR,13C-NMR and EI-MS. They were respectively friedelin (1), glut-5-en-3β-ol(2), β-sitosterol(3),1-pentacosa-nol(4), stearic acid(5). It is the first time that these compounds are isolated from this plant, glut-5-en-3β-ol (2) and1-pentacosanol (4) are isolated from this genus for the first time. The MICs were determineed for these compounds by broth micro-dilution method, the results showed that these five compounds had no antibacterial activity with the MICs were greater than1000μg/mL.