Isolation of plant natural products of potential chemotaxonomic significance and medicinal value

This thesis reports on the application of a rapid and simple pressurised hot water extraction (PHWE) method that utilises an unmodified household espresso machine to extract structurally-diverse natural products from plant material. The core focus of this thesis was the use of PHWE to expedite phytochemical screening of native Tasmanian and Australian plants and facilitate natural product isolation. The introduction features reviews on two key topics that are pertinent to the research described in this thesis. The first review summarises all natural product isolation studies of endemic Tasmanian vascular plants, which provides context for subsequent studies. The second review provides an overview of the applications of accelerated solvent extraction (ASE‚Äöv묢) and PHWE methods for the isolation of natural products. PHWE was employed to develop phytochemical profiles of several endemic Tasmanian Proteaceae members. This includes the identification of novel arbutin derivatives in ancient Tasmanian Proteaceae genera that may represent potential chemical markers. The phytochemical profiles of endemic Tasmanian Lomatia species were also studied. PHWE enabled the rapid and effective extraction and isolation of gram-scale quantities of the glycoside asperuloside from the native Australian Coprosma quadrifida. In addition, PHWE was employed to extract the leaf material of Australian carob cultivars, from which a novel tannic acid derivative was isolated. Natural product isolation studies of the native Australian Dodonaea viscosa using PHWE and traditional maceration afforded various ent-labdane diterpenoids. PHWE of Myoporum montanum was also identified as an effective tool for the isolation of known furanosesquiterpenoids. The rapid PHWE method facilitated the extensive sampling of Tasmannia lanceolata (Tasmanian native pepper) across diverse wild Tasmanian populations. Notably, this work identified the presence of two distinct chemotypes of drimane sesquiterpenoids.