Blanchfield, JoanneSaqer, Alaa2024-07-012024-07-012024-06-25https://hdl.handle.net/20.500.14154/72414Herbal and natural medicines have long been a critical part of medical practice. Medicinal plants are a rich source of bioactive phytochemicals. This project aimed to investigate the phytochemistry of two native Australian plants, Cymbopogon procerus and Asparagus racemosus, from the Northern Territory. In our project, we investigated the phytochemistry of plant material via extraction, fractionation of crude extract through solid phase extraction (SPE) and purification of compounds using reverse phase high-performance liquid chromatography (RP-HPLC). Compounds are then identified using analytical techniques, including one and two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) and liquid chromatography mass spectrometry (LCMS). Cymbopogon procerus (native lemon grass) contained phenylpropanoids and volatile aromatic terpenes. A total of 16 known compounds, including phenylpropanoids compounds (2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10, and 2.11), C11-terpene lactone (2.12), truncated sesquiterpenes (2.13, 2.14), cis-3-hexenyl-β-D-xylose (2.15) and fatty acid (2.16) were isolated from this species. Among these compounds, twelve compounds (2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15 and 2.16) were reported for the first time from C. procerus. The methanolic extract of stem and grass parts of this plant displayed high antimicrobial activity against Burkholderia humptydooensis and Staphylococcus aureus. The phytochemistry of the native Asparagus racemosus, from two locations in Australia, consists of saponins, the major bioactive compounds responsible for many medicinal properties of this herb. A total of twenty compounds were isolated from this species, including four new spirosteroids, asparacemosone E (3.1), asparacemosone F (3.2), asparacemosone G (3.3), asparacemosone H (3.4) and one new sulphated saponin, filicinoside sulphate B (3.7), one known spirosteroid (3.5), one known aromatic compound (3.20), and thirteen other known saponins (3.7, 3.8, 3.9, 3.10, 3.11, 3.12, 3.13, 3.14, 3.15, 3.16, 3.17, 3.18, and 3.19). Four of these compounds were isolated for the first time in A. racemosus; these were 25R-spirostan-4-ene-3,12-dione (3.5), filicinoside B (3.7), disporoside D (3.14) and trigoneside III (3.15). The structures of isolated saponins contained either furstanol aglycone or spirostanol aglycone (sapogenin) with varying degrees of glycosylation. This study also provided a baseline for comparative studies of native A. racemosus from two locations in Australia and India which confirmed a variation in saponin constituents and concentrations in roots collected at different locations based on retention times and comparisons with published data. Finally, an in vitro intestinal bioavailability model, the Caco-2 cell monolayer permeability assay, was used to predict the bioavailability of saponins isolated from A. racemosus (compounds 3.10, 3.11, and 3.12) with variations in sugar moieties attached to the aglycone. Compounds (3.11, 3.12) showed low permeability across Caco-2 monolayers, while compound (3.10) exhibited high permeability across Caco-2 monolayers. Therefore, compound 3.10 is a strong candidate for human oral bioavailability, possibly due to sugar transporters but this hypothesis is yet to be tested.273enCymbopogon procerusAsparagus racemosusNMRsaponinsphenylpropanoidsnatural productsCaco-2.Thesis