Development of pressurised hot water extraction for isolation of natural products

This thesis reports on the development of a rapid, efficient, and inexpensive pressurised hot water extraction (PHWE) technique, and its use to extract valuable natural products from plant material. Further, the use of natural products as scaffolds for divergent synthesis of known natural products and other complex molecules is described. The PHWE method uses a standard benchtop espresso machine, and was developed and refined through the extraction of polygodial from Tasmannia lanceolata (Tasmanian native pepper) and shikimic acid from Illicium verum (Chinese star anise). The former is a relatively non-polar sesquiterpene dialdehyde containing some sensitive functionality, and the latter is a much more polar carboxylic acid. These substrates proved to be useful for method development, and provide valuable complex scaffolds for synthetic applications. Applications of the espresso machine extraction method for rapid bioprospecting and chemotaxonomic applications were investigated through the extraction of a unique population of T. lanceolata, and extraction of Drimys winteri. This novel PHWE method was also applied to the extraction of known biologically active extracts such as that of Momordia charantia (bitter melon), Eupatorium adenophorum (Crofton weed), and Chrysanthemum cinerariaefolium (Dalmatian chrysanthemum, contains pyrethrins). Additionally, the use of the PHWE technique for essential oils was investigated. Many common plants were extracted, rapidly providing enriched essential oil extracts. The extraction of eugenol and acetyleugenol from cloves was implemented into the undergraduate laboratory program as a result of this work. The reactivity of polygodial was investigated extensively through the synthesis of some simple natural products based on this skeleton, in addition to various analogues. More complex polycyclic structures based on polygodial were also synthesised to investigate the level of stereospecificity achieved in reactions on this scaffold.