The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.

Magister Scientiae (Biodiversity and Conservation Biology) / This study investigated the role of grazing as a possible cause for the upper limit of distribution of algae on a typical South African south coast. / South Africa

Doctor Scientiae (Biodiversity and Conservation Biology) / The purpose of this thesis was to provide a revision and characterization of the species of nongeniculate coralline algae previously ascribed to the now defunct genus Porolithon; to provide a modern account of selected taxa from the genus Hydrolithon and descriptions of taxa found to conform the generic delimitation of Hydrolithon and to use a phenetic cluster analysis to determine the taxonomic relationships between the various taxa ascribed to the genera Polorithon and Hydrolithon. / South Africa

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 comprehensive field and laboratory study of nitrogen uptake in intertidal seaweeds was undertaken. Methods for measuring nitrogen uptake rates were evaluated. Short initial periods of rapid ammonium uptake were common in nitrogen deficient plants. The presence of ammonium inhibited nitrate uptake, but a certain degree of nitrogen starvation overcame this suppression. Laboratory studies with Porphyra perforata showed that nitrogen starved cultures maintained rapid initial ammonium uptake rates. The nitrate uptake system did not remain activated. Nitrogen starvation also resulted in a general decrease in soluble nitrogen content and a transient increase in nitrate reductase activity. The effectiveness of in vitro and in vivo nitrate reductase assays was investigated. The rate of nitrite production in the in vivo assay varied with incubation time. Therefore, the in vitro assay was used. Nitrate grown cultures of Porphyra perforata maintained high ammonium uptake rates. It was suggested that the rate of nitrate reduction was limiting the supply of nitrogen for further assimilation which may control ammonium uptake. Ammonium arid ammonium plus nitrate grown cultures had very low nitrogen uptake rates and nitrate reductase activities. Field studies with Gracilaria verrucosa confirmed that growth on ammonium inhibited nitrate uptake, nitrate accumulation and nitrate reductase activity. The presence of ammonium did not inhibit nitrate uptake rates in severely starved populations. All populations maintained high ammonium uptake rates suggesting that they were nitrogen limited at this time (August). Ammonium and nitrate uptake were saturable in the high intertidal G. verrucosa population but not in the low intertidal population. An investigation was made into the effect of nitrogen source and periodic exposure to air on growth, development and nitrogen uptake in Fucus distichus germlings. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development. Ammonium and nitrate uptake rates of the germlings were much higher than for the mature thalli, but the affinity for nitrate was similar. The germlings showed saturable uptake kinetics but the mature thalli did not. The presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings. Mild desiccation enhanced nutrient uptake rates in several intertidal seaweeds. This uptake response occurred when growth was limited by that particular nutrient and when the thallus had been exposed to periodic desiccation for several weeks. The degree of enhancement, the percent desiccation producing maximum uptake rates and the tolerance to higher degrees of desiccation were related to intertidal location. This was shown to be an intraspecific as well as an interspecific adaptation. Transplant experiments with G. verrucosa showed that enhanced nutrient uptake rates after desiccation were related to intertidal height and not geographic location and that this response could be induced in approximately five weeks. It was suggested that this enhanced uptake response was an adaptation to nitrogen procurement and C/N homeostasis following periodic exposure when carbon was assimilated but when other nutrients were not available. / Science, Faculty of / Botany, Department of / Graduate

A preliminary electrophoretic study on Bangia vermicularis Harvey (Rhodophyta) along the coast of British Columbia was undertaken to determine whether enzyme banding patterns could be used to identify the relatedness of the populations which varied in chromosome number (3, 6 or 4) and life history (asexual or sexual). Material from nineteen sites was tested for seven enzymes: glutamate dehydrogenase (GDH); malate dehydrogenase (MDH); lactate dehydrogenase (LDH); superoxide dismutase (SOD), glucose 6-phosphate dehydrogenase (G6PDH); phosphoglucoisomerase (PGI); and phosphoglucomutase (PGM). Unlike higher plants, some of the banding patterns obtained in Bangia could only be explained if the enzymes SOD, GDH, LDH and PGI are monomers and the enzymes PGM, SOD, GDH, PGI, and G6PDH have only one cellular location. Generally, with the exception of two enzymes, PGI and G6PDH, which were highly polymorphic, only one to three bands were evident. Considerable amounts of variation in the mobility of the isoenzymes were detected between populations independent of chromosome number or sexuality. Contrary to expectations, often populations with three chromosomes or six ' chromosomes had the same number of loci and many of the three chromosome populations had some banding patterns indicative of diploids. Consequently, if there had been a polyploid origin of the six chromosome populations then there must also have been many gene duplications in the three chromosome populations. Alternatively, if the three chromosome populations arose by aneuploid reduction within a six chromosome population then there must also have been gene silencing and/or the formation of null alleles. Populations that were very close geographically differed to a large extent suggesting that there may be little gene flow between populations. The variability between populations could be explained by isolation over long periods of time during which changes could have occurred in the structure and regulation of the enzymes tested. / Science, Faculty of / Botany, Department of / Graduate

No description available.

No description available.

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.

Pentachlorophenol (PCP) is a chlorophenol with a pronounced biocidal activity that has led to its use in a number of applications. It was introduced in the 1930s as a preservative for timber and lumber and since then has found wide use as a biocide in agricultural and industrial applications. Many different physical, chemical and biological methods have been tried for the removal of PCP from wastewater. However, using microalgae for the removal of PCP and other organochlorine compounds from water may prove to be a cheaper alternative and give complete degradation of the compounds. The aim of this project was to study the efficiency of microalgae to degrade PCP. An algal strain named VT -1 and a bacterial strain named AT -14 were isolated from PCP containing conditions in the laboratory. The growth of VT -1 in the presence of PCP was compared with Chlorella emersonii and Chlorella vulgaris in two different autotrophic media. It was observed that VT-1 had the highest IC50 value of 25-26mg }-l PCP and EC50 value of 11.3mg }-1 PCP in S&K medium. With glucose as an additional carbon source the IC50 value for VT-1 in S&K medium was 29-30mg t 1 PCP. Bacterium AT-14 could grow in the presence of PCP, only with glucose as a carbon source. Mineralization of PCP by VT -1 and the two Chlorella strains was compared by using 14C_PCp. With all the three algae exposed to 14C_PCp, only VT-1 showed release of 14C02, which was evidence of mineralization of PCP by VT-1 which occurred only in the presence of light. Bacterium AT-14 did not produce 14C02. However, the consortium of VT-1 and AT-14 showed enhanced 14C02 evolution in the presence of glucose. The release of chloride ions from PCP can also indicate PCP dehalogenation and degradation. The evolution of 14C02 lagged behind chloride release (90 %) indicating that dechlorination of PCP could be the first step in its biodegradation. Breakdown of PCP was also followed by its extraction from the cells and medium. Normally dichloromethane (DCM) was used to extract PCP. The changes in the label extracted in DCM and iso-butanol were studied under different light condjtions, which showed that the 14C counts in DCM reduced and those in iso-butanol extract increased with time. The 14C counts in the iso-butanol extract could be a metabolite of PCP which is more hydrophilic. VT-1 appeared not to degrade PCP completely, since only 15% of 14C was recovered as 14C02. It appears that intermediates are formed which are distributed in the growth medium and in the biomass. It can thus be concluded that VT -1 is tolerant of PCP, appears to dechlorinate PCP and then releases some part of it as CO2.