Phytochemical screening and guided natural products isolation facilitated by liquid chromatography and mass spectrometry

<p dir="ltr">This thesis reports natural products isolation studies of<i> Dodonaea viscosa</i> spp. <i>Spatulata. D. viscosa</i> is native to Australia and is a known, rich source of <i>ent-</i>labdane diterpenoids. This species exhibits considerable intraspecific variation in its phytochemistry. Consequently, <i>D. viscosa</i> plant individuals within and across different populations in Hobart, Tasmania were sampled. The core focus of this thesis was to construct a library of <i>ent</i>-labdanes that would enable efficient phytochemical screening of <i>D</i>. <i>viscosa</i> extracts and potentially guide the isolation of novel <i>ent-</i>labdanes. It was anticipated that this would be facilitated by employing high-performance liquid chromatography coupled with mass spectrometry and ultra-violet detection (HPLC-UV-MS) analysis.<br>The phytochemical profiles of <i>D. viscosa</i> in this study exhibited considerable intraspecific variation, which led to the isolation of an array of terpenes. This includes five furano-<i>ent</i>-labdanes, two of which are previously unreported; four <i>ent</i>-labdane acids, one of which is previously unreported; one novel alcohol-containing <i>ent-</i>labdane and one unreported aldehyde-containing <i>ent</i>-labdane; four known <i>ent-</i>kauranes; viridiflorol; bicyclogermacrene; one previously reported triterpenoid; and two unprecedented monoterpenoids bearing fatty acid chains. A HPLC-UV-MS method was developed to assess crude extracts rich in <i>ent</i>-labdanes. This method was employed to build a HPLC-MS library with <i>ent-</i>labdanes and <i>ent-</i>kauranes isolated from various <i>D</i>. <i>viscosa</i> plant individuals. Applications of the developed HPLC-MS method for rapid screening were investigated through the analysis of three populations of D. <i>viscosa.</i> This resulted in the identification of different diterpenoids in these extracts. HPLC-MS analysis enabled rapid identification of <i>ent-</i>labdanes and <i>ent-</i>kauranes in plant extracts, which can be potentially applied to facilitate the isolation of novel diterpenoids, such as <i>ent-</i>labdanes, in the future.</p>