Studies on antibacterial and antifungal activities of selected Tanzanian marine algae

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University of Dar es Salaam
Presence of biologically active substances was investigated from 26 marine algae from the Dar es Salaam coast. Their crude extracts were tested for the suppression of growth of bacteria (8 species) and a fungus. Antimicrobial activity was found in 24 alaga. Strong activity was found in Acanthiphora spicifera, Gracilaria fergusoni, Cystoseira myrica and Valonia aegrophila. TLC-bioautography for crude extracts of 16 algae was done using Bacillus subtilis as a test organism. 15 algae were shown to have antimicrobial activity attributed to more than one compound. The change of activity towards different test microorganisms with storage time of the crude extract also indicated a multisubstance influence for their activity. Toxicity of crude extracts from 16 marine algae was investigated. Extract from Acanthophora spicifera, Gracilaria fergusoni, Cystoseira myrica, Gracilaria corticata and Ulva pertusa were found to be toxic to Artemia salina with Lc50 ranging fron 116-434 ug/ml. The other algae had LC50 far above 1000 ug/ml. Seasonal changes on antimicrobial production was also investigated. The studied algae: Gracilaria carticata, Laurencia papillosa and Sargassum aquifolium were shown to have seasonal variation of this attribute. Highest content of antimicrobial substances were found during December and January and lowest levels in April and July. Isolation of antimicrobial compounds was also done. Three active compounds were isolated from Sargassum aquifolium and one compound from each of the species Laurencia papillosa and Gracilaria corticata. Minimum inhibition concentrations (MIC) of these isolates range from 2.9-66 ug/ml and their minimum microbicidal concentrations (MMC were tested against Bacillus subtilis. The isolates were also toxic to newly hatched Artemia salina larvae. Their LC50 ranged from 183-408 ug/ml. From th results of Nuclear Magnetic Resonance (H-NMR and 13C-NMR). Infra Red Spectra, Ultra Violet Spectra and Gas Chromatograph- Mass Spectrogram (GC-MS) an isolate from Laurencia papillosa was identified to be an alcoholic chamigrene with relative mass of 319. The compounds from Sargassum aquifolium were found to be lactones. The account given in this thesis begins with the literature review about the algal pharmocological agents, isolations done, various antimicrobial extractions, bioassay, isolation and identification methods employed. This will hopefully give the reader sufficient background information regarding efforts devoted to these marine organisms and their potential. The review is followed by a statement on the escope of the study and the working hypotheses. Thereafter, follows a description of the source of materials used and the research methods employed, the results of the study and the discussion of the results. Then, the major research findings and the conclusions reached together with recommendations for future research are summarized. It is anticipated that this publication will contribute to the general knowledge of antibacterial, antifungal and cytotoxic substances which may facilitate further development of new and more potent drugs.
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Antibacterial agents, Antifungal agents
Mtolera, M. S. P. (1991) Studies on antibacterial and antifungal activities of selected Tanzanian marine algae, Masters dissertation, University of Dar es Salaam. Available at (