Chemical constituents and bioactive secondary metabolites from soft corals

Lim , Chen Fong (2010) Chemical constituents and bioactive secondary metabolites from soft corals. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Soft corals (phylum Cnidaria, class Anthozoa, subclass Octocorallia) are found worldwide, more in tropical coral reefs as compared to the temperate coral reefs. Unlike Scleractinian coral, soft coral does not have internal calcium carbonate skeleton. Therefore, soft coral contains chemical compounds in their body tissues, which are known as secondary metabolites that play an important role in their defense, and some of them also exhibited pharmacological activity. Research was carried out on four populations of Dendronephthya sp. from Sepanggar Island and one population of Lobophytum sp. from Banggi Island. Samples were extracted to obtain their crude extracts and chemical profiling of these extracts were carried out. Dendronephthya sp. with spiky morphology was found to contain very little secondary metabolites, with morphology similarity among the species and was not easily identified in the field. Further, microscopy studies were done using stereomicroscope and Scanning Electron Microscope (SEM). Observation showed differences in arrangement of spikes among the species. Dendronephthya Spl and Sp2 had similar morphology while spike arrangement of Dendronephthya Sp3 and Sp4 were different from Spl and Sp2. Samples were also subjected to extraction and only the primary metabolites were successfully isolated. Sterols isolated from every sample showed the same HPLC spectrum. Fatty acids, which were another isolate of these specimens, were analyzed using cluster analyses and presented in dendrogram. Dendrograms of monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and selected fatty acids biomarker (C15: 1, C18:1n9t, C18:1n9c, C24:1, C18:2n6t, C18:3n3, C22:6n3) showed that Dendronephthya Spl and Sp2 had the closest correlation followed by Sp3 and then Sp4. These results were similar to the findings from microscopy observation. Therefore, fatty acids can be used as chemotaxonomy biomarker for these particular four populations of Dendronephthya sp. Sterols isolated from these Dendronephthya sp could be used as a "finger-print" profile in identification of this genus. Meanwhile, the Lobophytum sp. showed numerous secondary metabolites from the chemical profile. Based on the chemical profiles, extracts of Lobophytum were subjected to isolation of their pure metabolites. Four pure metabolites were isolated and each of the metabolites was tested for their antibacterial activities. Three metabolites from Lobophytum sp. showed positive results against five marine environmental bacteria and two human pathogenic bacterium. Apart from that, all the metabolites tested showed insignificant antioxidant activities. Isolated metabolites were subjected to spectroscopic analysis and their structures were determined to be cembrene. Out of the four cembrenes from this Lobophytum sp., three were found to be novel.

Item Type:Thesis (Masters)
Uncontrolled Keywords:soft coral, tropical coral reef, pharmacological activity, bioactive secondary metabolite, spectroscopic analysis, chemical constituents
Subjects:Q Science > QL Zoology
Divisions:SCHOOL > Borneo Marine Research Institute
ID Code:6526
Deposited By:IR Admin
Deposited On:09 Jul 2013 12:14
Last Modified:09 Jul 2013 12:14

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