Thesis (doctoral)--Rijksuniversiteit te Leiden, 1998. / Acknowledgements and foreword inserted. Includes bibliographical references (p. 173-196).

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 91-99). Description: xi, 99 leaves : ill., maps ; 29 cm.

In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.

A commercial extract of kelp, Ascophyllum nodosum (L.) LeJolis, was applied as a foliar spray on third and fourth cutting alfalfa (Medicago sativa L.) in fertilized and nonfertilized plots. Kelp treatments alone had no effect on alfalfa yield and quality, on tissue levels of nitrogen, phosphorus, and potassium, or on populations of potato leafhopper (PLH), Empoasca fabae (Harris). For the fourth cutting, fertilizer and kelp*fertilizer effects were observed. Yield and tissue levels of potassium were higher and PLH numbers were lower in fertilized plots. In fertilized plots, kelp temporarily reduced numbers of PLH adults one week after kelp treatment, followed by lower numbers of PLH nymphs. In nonfertilized plots, PLH adult levels were initially higher, followed by increased numbers of nymphs. The number of fungal leaf spots on the top five leaves was lower on fertilized plants than on nonfertilized plants, on kelp-treated plants in nonfertilized plots, and on plants treated with the insecticide dimethoate compared to nontreated plants. Extracts of kelps, A. nodosum and Durvillea potatorum (Labill.) Aresch., were applied to cantaloupe (Cucumis melo L.) plants grown under three nutrient regimes. Kelp treatment lowered the tissue concentration of total nitrogen in one instance, but had no effect on nitrogen deficiency symptoms which were present in all plants. Kelp treatment slightly reduced phosphorus and increased boron and magnesium concentrations in plant tissue. Both kelp sprays increased dry root weights; A. nodosum also increased dry shoot weights and root:shoot ratio; D. potatorum decreased root rot. These kelp effects were most prominent in plants receiving the mid-level nutrient concentration. / M.S.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

No description available.

No description available.

Graduation date: 2001

Following surveys of seaweeds in Oregon and the Caribbean, four algal species were selected for study on the basis of their crude extract biological activity or thin-layer chromatographic characteristics. Extracts were fractionated by normal phase chromatography, including high performance liquid chromatography (HPLC). Derivatives (methyl esters, acetates, and benzoates) of natural products were produced to facilitate isolation or structure elucidation efforts. Structure proofs utilized high-field nuclear magnetic resonance (NMR) spectroscopy, including hetero- and homo-nuclear two-dimensional experiments. Infrared and ultraviolet spectra, optical rotations, mass spectra, and circular dichroic spectroscopy were also employed. The Puerto Rican red alga Murrayella periclados was found to contain (12S)-hydroxyeicosapentaenoic and (12S)-hydroxyeicosatetraenoic acids, two mammalian autacoids for which new biological activities are reported. Further eicosanoid metabolism was demonstrated by the isolation of (6E)-leukotriene B₄ and two diastereomers each of the insulin-release mediators hepoxilin B₃ and B₄. The Oregon green alga Acrosiphonia coalita also was found to contain novel fatty acid-derived substances. Some of these contain an unprecedented structural feature, a conjugated trienal in which the aldehyde moiety branches off from the fatty acid chain. Exciton chirality studies of benzoate derivatives indicate that the alga introduces oxygenation in the 9R, 13S, and 16S positions on precursor polyunsaturated fatty acid chains. The Oregon red alga Laurencia spectabilis was found to produce an equilibrium mixture of (±)-2-hydroxy-2-methyldihydrofuran-3-one and 5-hydroxy- 2,3-pentanedione, which dimerizes on silica gel to produce spiro-bis-pinnaketal, a compound which was previously reported from L. pinnatifida and is probably an artifact of isolation. The Oregon red alga Prionitis lanceolata displays high levels of apparent tryptophan metabolism. Never before isolated from a plant or marine source, 3- (hydroxyacetyl)indole, active at 10⁻¹⁰ M in the lettuce-seedling root elongation assay, was isolated in 0.07% yield along with indole-3-carboxaldehyde (0.5%) and indole-3-carboxylate (0.04% ). / Graduation date: 1992

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 120-137).