| || || Chandra, Mayuri.|
| || || Secondary metabolites composition and geographical distribution of marine sponges of the Genus Dysidea |
Institution: University of the South Pacific.
Call No.: pac In Process
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: Dysidea species – Lamellodysidea herbacea, Dysidea arenaria, and Dysidea avara – from New Caledonia were chemically screened to identify the chemical constituents of these sponges. Each species exhibited a specific profile, thus grouping the three species chemically together in distinct taxa. The screening also identified the presence of three different chemical types of L. herbacea present within the same region, New Caledonia. The pattern of occurrence of polybrominated diphenyl ethers (PBDE) in L. herbacea was also mapped for distant geographical sites, which included New Caledonia, Vanuatu, Fiji Islands, Solomon Islands, Moorea Island in French Polynesia, and Mayotte. Comparison and analysis of the chemical fingerprints shows that all the samples belong to the bromo-chemotype of compounds, and similarities and differences exist within the same species in different geographical locations. L. herbacea was further explored for compound isolations and characterization to verify the chemical fingerprints of these sponges. Spectroscopic and chemical analyses confirmed the presence of PBDEs in the L. herbacea analyzed. Eight different PBDEs have been identified, where four of these (compounds 2, 6, 7, and 8) have been successfully isolated and characterized. Crude extracts of the Dysidea sponges were also tested for activity against the fungi Cryptococcus neoformans and Candida albicans. Most extracts were active against Cr. neoformans hence confirming the hypothesis that the action was due to the inhibition of the proper functioning of the protein farnesyl transferase (PFT), which is an essential enzyme in the metabolism of this fungus. Ca. albicans is able to survive even without PFT. Since Plasmodium falciparum (the malarial parasite) is also dependent on PFT for survival, this anti-fungal test is being developed to be used as a pre-test for anti-plasmodial studies.