Studies of the secondary metabolite content of Tasmanian Caulerpa species

Five species of Tasmanian green algae have been investigated for their biological activity and secondary metabolite content. A total of thirteen novel secondary metabolites and eleven known secondary metabolites containing acetoxybutadiene, dialdehyde or related moieties have been isolated and identified. From Caulerpa trifaria the novel secondary metabolites have been characterised whilst the known secondary metabolites have also been isolated. From unbranched specimens of Caulerpa brownii the novel secondary metabolites and the known secondary metabolites have been isolated. The metabolite has been isolated for the first time as a natural product. The novel teipenoid esters and the known secondary metabolites have been identified from branched specimens of Caulerpa brownii whilst the novel secondary metabolites and the known secondary metabolites have been isolated from Caulerpa flexilis. Methods for isolating a further six metabolites from C. flexilis are also described. A preliminary study of Caulerpa scalpelliformis and Caulerpa longifolia has resulted in the isolation of the ecologically important secondary metabolite caulerpenyne and associated compounds. Geographic, seasonal and other factors affecting the production of secondary metabolite production in the five Caulerpa species are discussed whilst the biological activities of extracts of the Caulerpa species and selected metabolites are also described. The biological activities of the 1,4-dialdehyde, acetoxybutadiene and related moieties and the relationship between the secondary metabolites contained in the Caulerpa species C. C. triftwia and C. brownii are also discussed. The associated pigments pheophytin a and b and the sterol cholesterol have also been isolated from several of the Caulerpa species studied for this thesis.