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Functional biogeography: evaluating community assemblage patterns and ecosystem functioning in intertidal systems using trait-based approaches

  • Authors: Gusha, Molline Natanah C
  • Date: 2022-10-14
  • Subjects: Biogeography , Marine algae , Benthic ecology , Invertebrates , Functional redundancy , Ocean temperature , Biology Classification
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/365792 , vital:65790 , DOI https://doi.org/10.21504/10962/365792
  • Description: Analyses of taxonomic diversity patterns within coastal systems has been critical in the development of the theory of biogeography. Increasing evidence, however, shows that the variety of functions that species perform in ecosystems (rather than their taxonomic identity) is a better predictor of the influence of the environment on the species. This information has been useful in predictive ecology leading to the development of trait-based approaches (TBA). Until the late 1970s, however, limited effort (particularly in marine systems) was channeled towards patterns in functional species traits and how they may be affected by changes in environmental gradients. Here, I mapped the functional biogeography of the South African coastline based on a suite of species' reproduction and development traits. Because species composition is one of the key tools used by zoogeographers to map species distribution patterns, I expected lower variability in trait composition within main biogeographic regions than in intervening transition zones based on the habitat templet theory and following the biomass ratio and limiting similarity hypotheses. In brief, the habitat templet theory proposes that “the habitat provides a templet upon which evolution forges species characteristics”, while the biomass ratio hypothesis assumes that the most abundant species traits determine ecosystem functioning. The limiting similarity hypothesis also sometimes referred to as the niche complementarity hypothesis, however, predicts that species can coexist if their niches complement one another. In light of the habitat being an evolutionary templet, abiotic and biotic habitat patterns were measured as nearshore SST and chlorophyll-a gradients, respectively. I expected the SST gradient to act as the stronger key filter of trait diversification because temperature is often considered the most influential environmental factor affecting species survival with seasonality of SST affecting the timing of spawning and along with food availability, possibly influencing fecundity. Functional trait data were thus compiled for macroinvertebrate species collected from fifty-two rocky shore sites from three main bioregions (east, south, and west) and two transition zones (south-west and south-east). Biological trait analysis and functional diversity indices were used to evaluate how traits related to species development and reproduction respond to temperature and chlorophyll -a (used as a proxy for food availability) gradients along the coastline. GLMM and hierarchical cluster analyses showed distinct patterns/shifts in SST and chlorophyll-a gradients across bioregions, with two main breaks in SST separating the east and south-east overlap (SEO) bioregions from the south, south-west overlap (SWO) and west bioregions. In contrast, chlorophyll-a exhibited three major breaks with the east, SEO–south–SWO, and west clustering independently of each other. The RLQ analysis (a type of co-inertia analysis) which simultaneously ordinates 3-matrix datasets [i.e., (environment × site[R]), (species × site[L]) and (species × traits [Q])] showed that the higher SST gradient on the east and SEO promoted higher abundance and biomass of simultaneous hermaphrodites while higher chlorophyll-a gradients on the SWO and west coasts strongly promoted reproductive maturity at larger-sizes. The combined fourth-corner analyses showed that the modalities within the development trait domain responding to chlorophyll-a gradients primarily included filter feeders, sessile and swimming species and also species living on the infratidal zone. In addition, the reproduction trait domain showed higher sensitivity and association to differences in chlorophyll-a and SST gradients than development traits. Overall, SST and chlorophyll-a gradients influenced the distribution of the most dominant traits as indicated by shifts in community-weighted mean trait values across bioregions. This suggests the importance of habitat filtering on coastal species reproduction. A separate study evaluating the influence of large-scale biogeographic effects vs the micro-scale biogenic habitat structure offered by coralline seaweeds across 24 sites revealed some notable effects of both factors on the diversity and abundance of macroalgal epifauna. There was a notable biogeographic influence on epifauna, with the SEO recording the highest epifaunal species richness and abundance, followed by the south coast, then the SWO and lastly the west coast. In addition, the total biomass gradient of the corallines followed a similar trend. The epifauna however, showed no host-specificity, illustrating that epifauna may not be species–centric as commonly assumed, and the higher diversity of epifaunal diversity may well be simply because those corallines are the available habitat within the sampled part of the coastline. Lastly, macroinvertebrate trait distribution on the South African coastline confirms that the habitat, particularly the biotic filter (in this case chl-a) provides a templet upon which evolution forges species traits. However, since temperature is a proxy for nutrient availability (cold upwelling brings nutrients), then temperature drives chlorophyll-a. Subsequently this means the abiotic component indirectly drives trait distribution by influencing the biotic environment (chl-a). For epifauna species, also, the coralline diversity and composition can also be regarded as a biotic filter influencing the epifaunal abundances and composition across different bioregions. Moreover, since temperature is regarded as a conservative trait in seaweeds, temperature tolerance defines the biogeographical boundaries of seaweeds, therefore temperature may be indirectly affecting epifauna abundances through coralline species diversity and biomass. In summary, considering the deterministic processes governing ecosystem functioning and community assemblage, the mass ratio and limiting similarity hypotheses showed complementary effects. Different bioregions provided variable support for these two hypotheses, but overall, the mass ratio hypothesis (weighted by species biomass) received stronger support and may be more meaningful to the interpretation of ecosystem functioning and persistence within rocky shore systems. Lastly, although, the SWO showed some of the characteristics of a subtraction zone based on the relatively low abundance, diversity, and biomass measures. Nonetheless, there was evidence of high functional redundancy across all other four bioregions. This suggests that in the context of development and reproduction traits, the rocky shore ecosystem along the SA coastline may be functionally stable at this stage. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
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  • Date Issued: 2022-10-14

Evaluation of anti-diabetic activity of selected red marine macro-algae found along South African coastal areas

  • Authors: Bambo, Karabo https://orcid.org/0000-0002-3721-2424
  • Date: 2021-04
  • Subjects: Marine algae , Phytochemicals
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10353/22533 , vital:52405
  • Description: Marine macro-algae are a good source of potential primary and secondary metabolites. Phytochemicals of the samples were extracted using methanol and water. This study evaluated the phytochemical constituents, antioxidant activity and antidiabetic activity of selected red marine macro-algae sampled from Gqeberha, South Africa. The species collected were identified as Gelidium pristoides, Scinaia furcellata and Portieria tripinita using DNA barcoding. Results showed the presence of several phytochemicals such as saponins, phenols, flavonols, tannins, proanthocyanidins and flavonoids. Methanol was a more effective polyphenol extraction solvent than water. Gelidium pristoides (H2O) was observed to contain the highest phenol and proanthocyanidin content, which correlated to Gelidium pristoides (H2O) having the greatest FRAP and DPPH radical scavenging activity IC50 at 0.227. Portieria tripinita (MeOH) extract had the greatest flavonoid content. Flavonol content was high for Scinaia furcellata while the highest tannin content was observed in both H2O and MeOH extracts of Gelidium pristoides. All the selected marine macro-algae species showed concentration-dependent reducing power. The extract with the highest ABTS scavenging activity was Gelidium pristoides (MeOH) IC50 at 0.227. Portieria tripinita was the only species that showed Nitric oxide scavenging activity, with (H2O) extract showing the highest activity IC50 at 3.052. Only MeOH extracts of Gelidium pristoides and Scinaia furcellata showed very slight α-amylase inhibition, however, all extracts successfully inhibited the activity of α-glucosidase with the exception of the H2O extracts of Scinaia furcellata. All crude extracts of Gelidium pristoides, Scinaia furcellata and Portieria tripinita showed no significant/weak effect on glucose uptake and utilization by C3A cells following 24 hours of treatment, with the exception of the aqueous extracts of Scinaia furcellata at the highest concentration of 100 μg/ml. The in-vitro MTT cytotoxicity assay revealed that only MeOH extracts of Gelidium pristoides and Scinaia furcellata had a 15 significant toxic effect on C3A hepatocytes at concentrations of 100 μg/ml and 25μg/ml, respectively. Portieria tripinita aqueous extract showed cytotoxicity when evaluated using Hoechst 33342/Propidium iodide (PI) dual staining. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
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  • Date Issued: 2021-04

The quantification of fucoxanthin from selected South African marine brown algae (Phaeophyta) using HPLC-UV/Vis

  • Authors: Mubaiwa, Byron Tawanda
  • Date: 2015
  • Subjects: Marine algae , Brown algae , High performance liquid chromatography , Functional foods , Xanthophylls , Carotenoids , Extraction (Chemistry)
  • Language: English
  • Type: Thesis , Masters , MPharm
  • Identifier: vital:3868 , http://hdl.handle.net/10962/d1017879
  • Description: Marine brown algae (seaweeds) are a rich source of fucoxanthin, a xanthophyll carotenoid that is naturally, an accessory pigment in the process of photosynthesis of sea vegetation such as Sargassum incisifolium. Fucoxanthin has been exploited by nutraceutical companies for its anti-obesity effects that has resulted in an increase of seaweed slimming preparations such as FucoThin™. The field is getting widespread consumer attention as interest in fucoxanthin has also transcended to its widespread biological potential which include cytotoxicity, anti-diabetic, anti-oxidant, anti-inflammatory and anti-plasmodium effects. We therefore wanted to identify a reliable source(s) of fucoxanthin from diverse samples of South African marine brown algae in order to explore our medicinal chemistry interests around the cytotoxicity and anti-malarial potential of fucoxanthin. A known source, Sargassum incisifolium, was used to isolate (maceration in CH₂Cl₂/MeOH at 35 °C followed by a hexane/EtOAc step gradient silica column of the crude extract and reversed phase semi-prep HPLC) and characterize (1D and 2D NMR) fucoxanthin (reference standard) in order to develop an analytical method for its determination in selected diverse brown algae commonly found in South Africa. The HPLC [Column: Phenomenex® Synergi™ (250 x 3.0 mm i.d); Mobile phase: ACN/H2O (95:5)] method developed for this analysis was validated according the guidelines set by the International Conference on Harmonization (ICH). Fifteen species were then assessed for fucoxanthin content (μg/g of dried weight) using the developed method. Stability studies on fucoxanthin were also carried out to assess photo- and pH degradation of fucoxanthin. Zonaria subarticulata (KOS130226-18) from Kenton-On-Sea beach and Sargassum incisifolium (PA130427-1) from Port Alfred beach were found to be the highest producers of fucoxanthin with 0.50 mg/g and 0.45 mg/g dried weight respectively. Fucoxanthin was found to be both photo-labile and sensitive to both acidic and basic pH environments. However, the pigment was more photostable in pure as opposed to extract form and also showed to be more stable at pH 10.0. Our findings show that Z. subarticulata and S. incisifolium could be reliable sources of fucoxanthin and can be considered as the algae to use in optimized extraction procedures in further studies. Also, when working with fucoxanthin, it is important to protect it from light. Any consideration of taking fucoxanthin preparation orally (as a nutraceutical) should consider protecting the active from the harsh conditions of the gastrointestinal tract. Any upscale production of fucoxanthin from seaweed should consider variations such as geographical, seasonal, lifecycle stage, etc. of identified algae as these may be important factors in obtaining effective concentrations of fucoxanthin.
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  • Date Issued: 2015

An investigation of the potential anti-diabetic (insulinomimetic) activity of anti-oxidant compounds derived from Sargassum heterophyllum

  • Authors: Nyambe, Mutenta Nsokolo
  • Date: 2014
  • Subjects: Sargassum , Diabetes -- Chemotherapy , Diabetes -- Africa , Antioxidants -- Therapeutic use , Marine algae , Endemic plants -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3874 , http://hdl.handle.net/10962/d1021020
  • Description: In Africa, non-communicable diseases such as diabetes mellitus have been generally neglected. This problem has worsened over the years owing to continuous threats from infectious diseases such as HIV/AIDS, tuberculosis and malaria. Despite this, statistics have shown that by 2030, the African region will have the highest proportional increase in diabetes prevalence. Over 80% of all diabetic deaths occur in developing countries probably not only due to poor equity of access to medication but also due to limited efficacy and side effects associated with the commonly available anti-diabetic agents. Therefore, this creates the desperate need for the development of new anti-diabetic agents that are more efficacious and can be sourced from within the continent. With oxidative stress as a suggested mechanism underlying the cause of diabetes mellitus and diabetic complications, the discovery of natural anti-oxidants that prevent free radical mediated damage is important for developing new treatment strategies. Marine algae have been identified as good sources for natural anti-oxidants. Unfortunately, very few studies have embarked on the discovery of marine-derived anti-oxidant compounds with potential anti-diabetic activity. In this project, we investigated the potential anti-oxidant activity of the South African endemic algae Stypopodium multipartitum, Dictyopterus ligulata, Cystophora fibriosa, Bifurcariopsis capensis, Sargassum sp. and Sargassum heterophyllum. From these studies, Sargassum heterophyllum yielded prenylated compounds, the main compound being sargahydroquinoic acid (3.6) and the carotenoid metabolite fucoxanthin (3.8), which are in part responsible for the radical scavenging activity of the crude extract. Sargahydroquinoic acid (3.6) and fucoxanthin (3.8) also exhibited significant anti-inflammatory activity. Sargaquinoic acid (3.1), sargachromenoic acid (3.9) and sarganaphthoquinoic acid (3.10) were then semi-synthesized from sargahydroquinoic acid (3.6) and their in-vitro cytotoxicity profiles evaluated using Chang Liver, HT-29, Caco-2 and 3T3-L1 cell lines prior to antidiabetic testing. From the semi-synthetic derivatives, sargachromenoic acid (3.9) exhibited the most potent anti-oxidant activity (IC₅₀ = 6.99 μg/mL). After the evaluation of antidiabetic activity using 3T3-L1 preadipocyte differentiation, sarganaphthoquinoic acid (3.10) showed the most potent insulinomimetic activity at 1.19 μM by inducing a PPARγ response similar to that of rosiglitazone at 1 μM.
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  • Date Issued: 2014

Contributions of inshore and offshore sources of primary production to the foodweb, and the trophic connectivity between various habitats along a depth-gradient, in Sodwana Bay, Kwazulu-Natal, South Africa

  • Authors: Parkinson, Matthew Cameron
  • Date: 2013
  • Subjects: Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5179 , http://hdl.handle.net/10962/d1001630 , Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
  • Description: Sodwana Bay, situated within the iSimangaliso Wetland Park, is ecologically important as it contains high-latitude corals and the most southerly known population of coelacanths. This thesis utilised stable isotope and lipid analyses to investigate the trophic ecology of the area, in particular, understanding the relative contribution of inshore and offshore primary production to consumers inhabiting intertidal and shallow subtidal, coral reef, deep reef, canyon head and pelagic habitats. Seaweeds, excluding certain species of red seaweeds with highly depleted carbon signatures, and phytoplankton, such as diatoms, were found to be the principal sources of primary production for all consumers. Offshore production was typified by dinoflagellates. Particulate organic matter (POM) was spatio-temporally variable. Three distinct productivity periods related to nutrient cycling were noted with enriched carbon signatures and higher organic matter loads associated with warmer water. Inshore primary production was an important source of carbon to consumers in all habitats with the exception of zooplankton that were more reliant on pelagic primary production. Benthic invertebrates reflected a gradient in the utilisation of inshore production, due to the reduced availability of this source further offshore. Consumers at the furthest sites offshore were found to include a substantial quantity of inshore-derived production in their diets. Fishes, which are more mobile, were found to incorporate a similar proportion of inshore production into their diets regardless of where they were collected from.
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  • Date Issued: 2013

An investigation of the antimicrobial and antifouling properties of marine algal metabolites

  • Authors: Mann, Maryssa Gudrun Ailsa
  • Date: 2008 , 2013-07-11
  • Subjects: Anti-infective agents , Marine metabolites -- Therapeutic use , Marine algae , Pharmacognosy , Fouling , Marine fouling organisms
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3831 , http://hdl.handle.net/10962/d1007465 , Anti-infective agents , Marine metabolites -- Therapeutic use , Marine algae , Pharmacognosy , Fouling , Marine fouling organisms
  • Description: Prevention of the accumulation of undesirable biological material i.e. biofouling upon a solid surface requires the use of antifouling systems. The solid surface may be a contact lens, an off shore oil rig or a living organism. When chemicals are employed as a mechanism of defense against biofouling, the agents involved are known as antifouling agents. Marine algae must protect themselves from fouling organisms and it is thought that one of the mechanisms used by these organisms is the production of secondary metabolites with an array of biological activities. In vitro studies have shown numerous compounds isolated from marine algae to possess antibacterial, antifungal and antimacrofouling activity. The aim of this study was to evaluate the secondary metabolite extracts of selected Southern African marine macro-algae as a potential source of compounds that inhibit biofilm formation and that could be used as antifouling agents. In this project, marine macro-algae were collected from various sites along the South African coastline. Their extracts were screened for antimicrobial activity against four ubiquitous microorganisms, Staphylococcus aureus, Klebsiella pneumoniae, Mycobacterium aurm and Candida albicans. Results of screening assays guided the fractionation of two Rhodophyta, Plocamium corallorhiza and Laurencia flexuosa. The algae were fractionated using silica gel column chromatography and compounds were isolated by semi-preparative normal phase HPLC. Compound characterization was performed using UV, IR and advanced one- and two-dimensional NMR (¹H, ¹³C NMR, COSY, HSQC, HMBC and NOESY) spectroscopy and mass spectrometry. Ten halogenated monoterpenes including four members of the small class of halogenated monoterpene aldehydes were isolated from extracts of P. corallorhiza. The compounds isolated included the known compounds 3,4,6,7-tetrachloro-3,7-dimethyl-1-octene; 4,6-dibromo-1, 1-dichloro-3,7 -dimethyl-2E,7 octadiene; 4,8-d ibromo-1,1,7 -trichloro-3, 7-dimethyl-2,5Eoctadiene;1 ,4,8-tribromo-3, 7 -dichloro-3,7-dimethyl-1 E,5E-octadiene; 8-bremo-6, 7-dichloro-3,7-dimethyl-octa-2E,4E-dienal; 4-Bromo-8-chloro-3,7-dimethyl-octa-2E,6E-dienal; 4,6- Dibromo-3,7-dimethyl-octa-2E,7-dienal; 2,4-dichloro-1-(2-chlorovinyl)-1-methyl-5-methylidene-cyclohexane and two new metabolites 4,8-chloro-3,7-dimethyl-2Z,4,6Z-octatrien-1-al and Compound 3.47. Methodology was developed for the chemical derivatization and mass spectrometric analysis of the aldehydic compounds, The aldehyde trapping reagent 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride was used to derivatize the molecules, stabilizing them and allowing for their complete characterization. From Laurencia flexuosa a new cuparene sesquiterpene 4-bremo-2-(5-hydroxy-1,2,2- trimethylcyclopent-3-enyl)-5-methylphenol was isolated along with two geometric isomers of the vinyl acetylene bromofucin , An halogenated monoterpene 3S*,4R*-1-bromo-3,4,8-trichloro-9-dichloromethyl-1-E,5-E,7-Z-octatriene was also isolated but was suspected to be a contaminant and an investigation into its biological source revealed that it originated from Plocamium suhrii. A third alga, Martensia elegans was extracted based on published reports of antimicrobial compounds in related species. A new a-alkyl malate derivative was isolated and characterized. Selected compounds isolated during the course of the study were employed in preliminary assays that tested their ability to inhibit biofilm formation by Pseudomonas aeruginosa. The halogenated monoterpenes isolated from the Plocamium species were the only active compounds. 3S*,4R*-1-bromo-3,4,S-trichloro-g-dichloromethyl-1-E,5-E,7-octatriene from P. suhrii inhibited biofilm formation through antibacterial activity on planktonic cells but could not prevent biofilm formation when employed as a film on the surface of microtitre plate wells. 1,4,8-tribromo-3,7-dichloro-3,7-dimethyl-1E,5E-octadiene and 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene inhibited biofilm formation when applied as a film to the microtitre plate wells but had no significant antibacterial activity. No potential antifouling agents were identified in this project but the antimicrobial activity exhibited by the crude algal extracts was highly encouraging and a number of new research areas have been identified. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 2008

Evaluation and application of electroanalysis for the determination of antioxidants

  • Authors: Ragubeer, Nasheen
  • Date: 2007
  • Subjects: Antioxidants , Nervous system -- Degeneration , Electrochemical analysis , Marine algae , Natural products , Marine metabolites , Sargassum , Legumes , Nuclear magnetic resonance
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3922 , http://hdl.handle.net/10962/d1003981 , Antioxidants , Nervous system -- Degeneration , Electrochemical analysis , Marine algae , Natural products , Marine metabolites , Sargassum , Legumes , Nuclear magnetic resonance
  • Description: The role of antioxidants in the prevention of neurodegenerative diseases has been well documented. The use of synthetic antioxidants has decreased due to the ssociation of these compounds with certain cancers. Thus, the search for novel natural antioxidants has gained much focus in research. Most common methods of determining antioxidant capacity are the radical generated assays and biological assays such as lipid peroxidation and the nitroblue tetrazolium assay. Electrochemical methods have been proposed for the determination of bio-active compounds such as antioxidants. The electrochemical methods of cyclic voltammetry and square wave voltammetry were evaluated for the determination of antioxidant capacity initially examining known antioxidants and then using plant extracts of Sutherlandia frutescens as a case study. The antioxidant properties determined by electrochemical methods were validated utilising the non-biological methods of the DPPH, TEAC, ferrozine and FC assay and biological pharmacological methods. The results indicated that Sutherlandia frutescens contains potent antioxidant compounds that are able to reduce lipid peroxidation. The electrochemical techniques of square wave voltammetry and cyclic voltammetry were applied for the screening of a large number of extracts of various algae for the detection of antioxidant compounds. The results indicated that electrochemistry can be used as a preliminary method for the rapid screening of a large number of crude samples for antioxidant compounds. Electrochemical methods were also evaluated as a method for guiding the isolation and purification of antioxidant metabolites in Sargassum elegans. Solvent partitioning and fractionation of the marine alga allowed for the purification of antioxidant compounds. At each step of purification electrochemical methods were utilized to determine which fractions contained the more potent antioxidant compounds and thus guide further purification. The purified antioxidant compounds were elucidated using NMR to determine the structure of the antioxidant compounds.
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  • Date Issued: 2007

A study of plocamium corallorhiza secondary metabolites and their biological activity

  • Authors: Mkwananzi, Henry Bayanda
  • Date: 2005
  • Subjects: Natural products -- Therapeutic use , Marine metabolites -- Therapeutic use , Marine pharmacology , Marine algae , Monoterpenes
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3841 , http://hdl.handle.net/10962/d1007666 , Natural products -- Therapeutic use , Marine metabolites -- Therapeutic use , Marine pharmacology , Marine algae , Monoterpenes
  • Description: Seaweeds of the genus Plocamium are known to produce a variety of halogenated monoterpenes. In addition to their ecological role as feeding deterrents, biological activities reported for these compounds include antibacterial, antialgal, antifungal and anticancer activities. An investigation of the non-polar extracts of the seaweed Plocamium corallorhiza resulted in the isolation of six known halogenated monoterpene compounds, 4-bromo-5-bromomethyl-1-chlorovinyl-2, 5-dichloro-methylcyclohexane (2.68), 1,4,8-tribromo-3 ,7-dichloro-3, 7-dimethyl-1,5-octadiene (2.67), 8-bromo-1 ,3,4,7-tetrachloro-3, 7-dimethyl-1,5-octadiene (2.66), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2,7-octadiene (2.64), 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2,5-octadiene (2.65) and 3,4 ,6,7-tetrachloro-3, 7-dimethyl-1-octene (2.63) as well as eight new compounds, including five halogenated monoterpene aldehydes. The new compounds were identified by 1D and 2D NMR spectroscopic techniques as: 8-Bromo-6,7-dichloro-3,7-dimethyl-octa-2,4-dienal (2.72), 8-Bromo-1,1,2,7-tetrachloro-3,7-dimethyl-octa-3,5-diene (2.70), 4,8-Dichloro-3,7-dimethyl-octa-2,4,6-trienal (2.74), 4-Bromo-8-chloro-3, 7-di methyl-octa-2, 6-dienal (2 76), 8-Bromo-4-chloro-3, 7-dimethyl-octa-2,4 ,6-trienaI (2.75), 4-Bromo-1,3,6,7-tetrachloro-3 ,7-dimethyl-octa-1,4-diene (2.71), 8-Bromo-1,3,4,7-tetrachloro-3,7-dimethyl-octa-1,5-diene (2.69), 4,6-Dibromo-3,7 -dimethyl-octa-2,7-dienal (2.73). All compounds were screened for antimicrobial activity, brine shrimp lethality and cytotoxicity towards oesophageal cancer cells. Compound 2.68 was toxic to brine shrimp larvae at a concentration of 50 μ/mL. It also showed promising activity towards oesophageal cancer cells with an IC₅₀, of 2 μg/mL.
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  • Date Issued: 2005

Studies on the bioactivities of selected Eastern Cape seaweeds

  • Authors: Carter, Anne Margaret
  • Date: 1994
  • Subjects: Marine algae -- South Africa -- Eastern Cape , Marine algae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4033 , http://hdl.handle.net/10962/d1004093 , Marine algae -- South Africa -- Eastern Cape , Marine algae
  • Description: 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.
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  • Date Issued: 1994

A study of the marine algal epiphyte, Placophora binderi (J. Agardh) J.Agardh (Ceramiales : Rhodophycophyta)

  • Authors: Hartley, Diana Hendy
  • Date: 1986
  • Subjects: Epiphytes , Marine algae , Codium , Ceramiales
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4177 , http://hdl.handle.net/10962/d1002025 , Epiphytes , Marine algae , Codium , Ceramiales
  • Description: Placophora binderi can be described as an "obligate epiphyte" as it does not respond well to any culture conditions and is found growing only on other algae in the natural environment. This habit may have arisen as a response to the best available substrate in a harsh environment (Harlin 1971; Moss 1982). Any nutrient transfer which may occur between Placophora binderi and its basiphyte, usually various species of Codium, is probably by diffusion as rhizoids do not penetrate the basiphyte cells but simply lie between the Codium utricles providing better anchorage. A triphasic life history exists with isomorphic gametophyte, carposporophyte and tetrasporophyte generations. The male and female gametophytes are dioecious. This study confirms Scagel's (1953) observations for the development of the juvenile, mature and reproductive thallus. The juvenile develops as an erect polysiphonous thallus which produces a prostrate lobe as an adventitious branch from the basal segments. This prostrate lobe develops into the dorsiventrally flattened mature thallus. Reproductive structures are produced on erect branches which are initiated at the mature thallus margins. The gametophyte develops on evanescent trichoblasts produced on erect reproductive branches while the tetra sporophyte develops within these erect branches. The female gametophyte has a four-celled carpogonial branch with an auxiliary cell forming after fertilisation from the supporting cell. At the electron microscope level several vesicle types were seen in the reproductive organs. In the male, spermatial vesicles are produced which probably aid in release of the spermatia (Kugrens 1980). These are also visible under the light microscope. In carposporogenesis and tetrasporogenesis, three vesicle types are produced. Striated vesicles appear for a short while during the early stages and probably function as protein stores. Fibrillar vesicles are large and visible under the light microscope. These probably act as carbohydrate storage organelles (Triemer and Vasconcelos 1979; Kugrens and West 1973c; Tripodi 1971). Cored vesicles appear late in sporogenesis and probably aid in adhesion once the spores have settled (Chamberlain and Evans 1973; Wetherbee 1978). Carpospores follow the "serial release" type pattern observed in Polysiphonia (Boney 1978). Tetraspores are released singly via a rupture in the tetrasporangial wall as in Ceramium rubrum (Chamberlain and Evans 1973). Both carpospores and tetraspores germinate in the typical bi-polar Ceramium-type pattern described by Dixon (1973)
  • Full Text:
  • Date Issued: 1986

Studies of Hypnea spicifera

  • Authors: Hewitt, Florence E
  • Date: 1955
  • Subjects: Marine algae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4271 , http://hdl.handle.net/10962/d1018234
  • Full Text:
  • Date Issued: 1955
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