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

This thesis reports natural products isolation studies of Dodonaea viscosa spp. Spatulata. D. viscosa is native to Australia and is a known, rich source of ent-labdane diterpenoids. This species exhibits considerable intraspecific variation in its phytochemistry. Consequently, D. viscosa plant individuals within and across different populations in Hobart, Tasmania were sampled. The core focus of this thesis was to construct a library of ent-labdanes that would enable efficient phytochemical screening of D. viscosa extracts and potentially guide the isolation of novel ent-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.
The phytochemical profiles of D. viscosa in this study exhibited considerable intraspecific variation, which led to the isolation of an array of terpenes. This includes five furano-ent-labdanes, two of which are previously unreported; four ent-labdane acids, one of which is previously unreported; one novel alcohol-containing ent-labdane and one unreported aldehyde-containing ent-labdane; four known ent-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 ent-labdanes. This method was employed to build a HPLC-MS library with ent-labdanes and ent-kauranes isolated from various D. viscosa plant individuals. Applications of the developed HPLC-MS method for rapid screening were investigated through the analysis of three populations of D. viscosa. This resulted in the identification of different diterpenoids in these extracts. HPLC-MS analysis enabled rapid identification of ent-labdanes and ent-kauranes in plant extracts, which can be potentially applied to facilitate the isolation of novel diterpenoids, such as ent-labdanes, in the future.