This thesis reports on the chemistry and anti-infective activity of the flowering plant family Myrtaceae (a family whose members dominate the Australian landscape). To understand the significance and importance of the Myrtaceae family from a phytochemical and medical perspective, a systematic literature review was carried out. The conclusion from this review was that the family is a major source of [beta]-triketone, phloroglucinol, and volatile terpene natural products with the [beta]-triketones in particular being a major focus of recent research. Over hundred new compounds from this class, many of which possess novel ring systems, have been reported in the last ten years. Furthermore their chemical diversity is matched with their high biological activity, most notably anti-infective activities including antiplasmodial, antibacterial and antiviral being reported for these compounds. All the findings of the literature review are documented in Chapter 2 of this thesis. As a result of this review the experimental research carried out in this dissertation focused on the antiplasmodial and antibacterial activity of natural product constituents isolated from the flowers of three Australian Myrtaceae plant species, Corymbia intermedia, C. torelliana, and Angophora woodsiana collected from South East Queensland. These plants were chosen because of the literature precedent for Corymbia species to be a major source of bioactive [beta]-triketones and although Angophora species have not previously been investigated their close taxonomic relationship to the Corymbia suggested that they would likely be an additional source of [beta]-triketone constituents. A total of 24 [beta]-triketone compounds, 14 of which are new, were isolated from methanol extracts of flowers of these three species. [...]