Date of Award
Ph.D. in Pharmaceutical Sciences
Mark T. Hamann
Kenneth J. Sufka
Jordan K. Zjawiony
The drug discovery process has become increasingly complex in comparison to early efforts particularly those involving diseases or conditions that affect large numbers of the human population. It is difficult to point directly to one factor leading evolution of the process but the definition of a mechanism of pharmacological action for a drug lead has noticeably become a higher priority. This evolution has helped diminish the stigma of natural products and compound supply issues. The issue of compound supply has also been addressed to some extent with the emergence of recombinant technologies and new synthetic methodology. With approximately 60 years of research performed after the development of SCUBA, the drug discovery opportunities in the sea are still too numerous to count. Since the FDA approval of the "direct-from-the-sea" calcium channel blocker Prialt (ziconotide), marine natural products has been validated as a source for new medicines. However, the demand for natural products is extremely high due to the development of high-throughput assays and this bottleneck has created the need for an intense focus on increasing the rate of isolating and elucidating new bioactive secondary metabolites. A cystine-rich peptide asteropusin A (ASPA) was isolated from the marine sponge Asteropus sp. and its structure determined by X-ray crystallography and NMR spectroscopy. Administration of ASPA to veratridine-stimulated cerebrocortical neuron cells enhances calcium influx but does not modify the oscillation frequency or amplitude of the neuronal calcium alone. Ion channel modulation is an emerging target for drug therapy and the discovery of an ion channel interacting knottin from Porifera accompanied by such high quality spatial details is an uncommon combination. Improvements made to the isolation of peptide metabolites from marine sponges of the Family Theonellidae enables the isolation of significant amounts of potential angiogenesis inhibitors like theopapuamide with high purity. The improvements are particularly relevant in future cases where nuisance components like the aurantoside dyes can lead to false indications of cytotoxicity or antifungal activity. The elucidation of a new theopapuamide analog by CID-MS from Theonella invaginata indicates the high level of peptide diversity found within this Family. Two functional studies of marine natural products contribute to the understanding of their mechanisms of biological activity which can provide insight into their future development as drugs. In the first study, aaptamine was found to possess anxiolytic effects in vivo using a chick anxiety model. A large number of neurological receptors and enzymes were screenedin vitro. In vivo functional challenges were then performed to validate the anxiolytic targetamong several putative candidates previously identified by the in vitro studies. The results of those challenges eliminated several anxiety linked receptor targets and indicated aaptamine as a modulator of monoamine oxidase inhibition activity in vivo as an alternative explanation. The second functional study evaluates new latrunculin B analogs and their correlation of predicted binding with G-actin to the inhibition of polymerization. The latrunculins are well-studied sponge derived inhibitors of actin polymerization and the results validate a method for in silico prediction activity this cancer drug target. Natural products which are isolated in high yields can imply the absence of a utility for humans considering that discovery efforts areprimarily focused on producing drug and agrochemical agents. However, compounds which are abundant in one organism imply an ecological impact that can be studied for the development of an alternative use. A significant quantity of fragrant oil was obtained from a Jamaican Plakortis sp. by cryo-trap. The oil was determined to be exclusively n-decan-2-one. The antifouling character of the oil was evaluated by its effects on surface attachment of a Gram negative bacterial model using confocal fluorescence microscopy as well as its effects on the attachment of Dreissena polymorpha (zebra mussel). The ketone ( n-decan-2-one) inhibited attachment of the bacteria and zebra mussels. Although the aliphatic ketone alone is not a potential commercial alternative for antifouling coatings, incorporating the functionality into coating design is a feasible alternative. The unusual amount of oil extracted from the imported fire ant ( Solenopsis sp.) may be an indication of the presence of oleaginous microorganisms or enzymes supporting the digestion of raw sugars. Heat of combustion of the ant oil was 133,000 BTU/gal, an amount within the range of reported values for vegetable oil and biodiesel. This investigation offers a unique perspective of a potentially new source of microorganisms or enzymes useful for reducing the cost of producing an alternative fuel.
Bowling, John Jason, "Functional Studies of Novel Bioactives From Complex Host-Microbiomes as Drug Leads for Cancer, Infectious Disease, Depression and Pain" (2012). Electronic Theses and Dissertations. 58.