The aim of this PhD thesis was to study the chemical composition of marine sponges collected from Mooloolaba, South-East Queensland, Australia. A series of known and new secondary metabolites have been isolated from various sponge sources including Pseudoceratina sp., Anomoianthella rubra, Dysidea sp. and a Plakortis sp. – Agelas mauritiana sponge association. A New South Wales collection of Ianthella sp. was re-investigated. The structures of the isolated compounds were analysed by extensive use of spectroscopic methods including 1D and 2D NMR, mass spectrometry and circular dichroism.
Collection of Verongiid sponges, namely Pseudoceratina sp., from the Pinnacles, Tani’s Reef, the Caves and Hanging Rock dive sites yielded a series of bromotyrosine metabolites from a simple modified tyrosine to more elaborate linear compounds. Seven known compounds, (+)-aeroplysinin-1 (2.4), a mixture of 19-deoxyfistularin-3 (2.24) and 11-deoxyfistularin-3 (2.26), 11,19-dideoxyfistularin-3 (2.19), 11-ketofistularin-3 (2.22), aerothionin (2.7) and homoaerothionin (2.8) have been isolated together with three new compounds, 11-deoxy-19-ketofistularin-3 (2.27), the new compound 2.28 and the acetal derivative of homoaerothionin (2.32). The relative stereochemistry was determined by comparison with literature spectroscopic data and the absolute configurations of some isolated compounds were deduced from CD spectra. Chemical study of Pseudoceratina sp. also gave a number of artifacts which might be due to the use of ethanol and water during extraction and isolation.
Sponges of the genus Ianthella are the prolific source of the bromotyrosine-based class of natural products known as the bastadins. Re-examination of Ianthella sp. collected from New South Wales, Australia clearly showed that this sponge species constantly yielded bastadins. A less studied sponge specimen from the family Ianthellidae, namely Anomoianthella rubra, has been chemically investigated. This Mooloolaba sponge collection yielded the known bastadin 13 (3.13), bastadin 16 (3.16), bastadin 21 (3.21) and a mixture of bastadin 6 (3.6) and bastadin 15 (3.15). The isolation of bastadin metabolites from Anomoianthella rubra showed that this sponge has potential to be a new source for bastadins.
A sponge of the genus Dysidea that was collected from Gneering Reef yielded a series of chromodorane diterpenes and a norrisolide-type compound. Two new chromodorolides, D (4.31) and E (4.32), together with the known chromodorolides A (4.28), B (4.29), C (4.30) and norrlandin (4.16) were isolated from this yellow encrusting sponge. The structure of norrlandin (4.16) was fully characterised for the first time by a complete assignment using 1D and 2D NMR analysis. Furthermore, the literature NMR for norrlandin was revised using 2D NMR techniques. Chromodorolides D and E were confirmed as the deacetylated analogues of chromodorolide A and chromodorolides B and C, respectively, by acetylation. The relative configurations of the tricyclic portion of chromodorolides D and E were assigned based on proton coupling constants and molecular modeling of their analogues. Biological evaluation of chromodorolides D and E indicated potent cytotoxic activity against P388 cells with IC50 values of 3.5 µg/mL and 1.9 µg/mL respectively.
A new cyclic peroxide 5.57 and the known peroxide with a C4-sidechain (5.59) have been isolated as a mixture with other components from a two sponge association of Plakortis sp. – Agelas mauritiana (Carter, 1883) collected from Mooloolaba. A bromopyrrole longamide (5.61) was also isolated as a racemate. To overcome issues in cycloperoxide purification, methylation using diazomethane was undertaken and afforded the corresponding methyl esters. Interestingly, the ring-opened analogues of the new cyclic peroxide (5.58) and the known peroxide with a C4-sidechain (5.60) were also obtained. Extensive analysis of 1D and 2D NMR and MS data, and comparison with literature data, has allowed characterisation of the structures. The relative stereochemistry of the isolated compounds was determined by the interpretation of the JH-H values and comparison of the 13C chemical shift data with literature data for related compounds.