Although the antomicrobial nature of essential oils and their major constituents, the terpenoids, has been widely investigated the mechanism of their antimicrobial action has not been subject to the same scrutiny. In this study the membrane disruptive nature of the terpenoids has been determined by experiments on the effects of terpenes on both microbial membrane and model lipid bilayer systems. These terpenes exhibited a range of membrane damaging effects. Experiments showed that the terpenoids were able to increase disorder in DPPC bilayers, and that antimicrobially active terpenoids cause increased membrane permeability in living cells. The effect of molecular structure on antimicrobial activity and activity differences between each organism were determined for 60 terpenoids. Terpenoids with a low water solubility were found to be inactive. Hydrogen bond donor capacity and hydrogen bond acceptor capacity were found to be the molecular parameters which most strongly discriminated between activities against individual organisms. Activity against Gram negative Escherichia coli and Pseudomonas aeruginosa was associated also with a molecular size parameter. The protective nature of the outer membrane of P. aeruginosa and E. coli was also investigated. The evidence presented in this thesis has enabled the postulation of a two stage process to explain the overall mode of action of these compounds. / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:ADTP/235040 |
| Date | January 2000 |
| Creators | Griffin, Shane G., University of Western Sydney, Hawkesbury, Faculty of Science, Technology and Agriculture |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Source | THESIS_FSTA_XXX_Griffin_S.xml |
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