Thesis (DTech(Chemistry)) --- Cape Technikon, Cape Town, 1996 / A new general synthetic strategy for the synthesis of benzo[c]pyranquinones, with a view to making the route more generally applicable to the synthesis of naturally occurring naphtho[2,3-c]pyranquinones of potential importance as antimicrobial agents, has been developed. This synthetic approach afforded, inter alia, the natural products, is oeleutherin and hongconin (as their racemates) in good overall yield. A new high-yielding synthetic route for the synthesis of 1,5-dimethoxy-4naphthol, 2-allyl-5-methoxy-I,4-naphthoquinone and 3-acetyl-5-methoxy-I,4naphthoquinone, all ofwhich are key intermediates in several laboratory routes to naturally occurring naphtho[2,3-c]pyranquinones, has also been developed. A key-step in their formation is respective methylation, allylation or acetylation of a common intermediate Diels-Alder adduct. A feasible route to a naphtho[2,3-c]pyranone was developed. This model route is envisaged to be generally applicable for the synthesis of higher oxygenated naphtho[2,3-c]pyranones by virtue ofthe nature of the conditions and reagents used in this synthetic route. The target quinones and some of their precursors were evaluated for antimicrobial activity and specificity in vitro. This showed that the benzo[c]pyranquinones have a broader specificity spectrum than their naphtho[2,3-c] or naphtho[2,3-b] analogues.

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)

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 5, 2007) Includes bibliographical references (p. 55-60).

A new form of antimicrobial surface was developed, which relies on an optical mechanism rather than chemical inactivation of microorganisms. Through the photoluminescence process of upconversion, low energy photons can be amplified into higher energy photons, and in this case, phosphors capable of converting visible light into germicidal UVC radiation were synthesized. Host crystals were doped with a praseodymium activator ion and shown to emit UVC photons upon excitation by blue or violet light. Surface coatings were prepared and proof-of-concept experiments demonstrated that, under exposure to a household fluorescent lamp, sufficient UVC radiation was emitted from the surfaces to achieve observable inactivation of surface bacterial spores and inhibition of biofilm growth. Material engineering was conducted to achieve higher optical conversion efficiency, wherein lithium codoping and development of alternative oxyfluoride host crystals were found to significantly improve upconversion emission. Implications of polychromatic excitation were investigated by conducting photoluminescence spectroscopy under combined laser beam excitation, while the effects of other application parameters are also discussed. These findings show that upconversion-based antimicrobial materials have strong potential for offering sustainable and effective technology for the prevention of diseases.

Thesis (Ph.D.)--University of Alberta, 2010. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Chemical and Materials Engineering, Medical Sciences - Biomedical Engineering. Title from pdf file main screen (viewed on January 30, 2010). Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.Sc.)(Botany)--University of Pretoria, 2004. / Summary in English. Includes bibliographical references.

Ph.d.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains vii, 113 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.