The main objective of this thesis was to study the effects of crude oil extracts on intertidal sediment communities. The approach was to focus on community structure and investigate the impact of a specific perturbation, crude oil extracts, relating to hypothetical oil spill situations. Both the impact of different disturbances on the same benthic community (i.e. with uniform structure) and the impact of the same disturbance on differently structured benthic communities were investigated. The effects on number of species, distribution of individuals between species and diversity were analysed, as well as recovery mode (trajectory of the system in time) and species arrival. The effects of different levels of a disturbance on an intertidal community were assessed, using water soluble fractions of crude oil (WSF) and two different concentrations of formaldehyde. The WSF had very little effect on community structure and recovery of the benthic community was prompt. The effects of the different concentrations of formaldehyde on the benthic community were indistinguishable: both concentrations had dramatic immediate effects. The relation between complexity and stability in benthic communities was evaluated by first setting-up two communities of different complexity using the equilibrium theory of island biogeography. After these different communities were established they were subjected to the effects of oil and dispersant. The impact of this perturbation on the two communities with different complexity was analysed both in terms of structure (as above) and functional level, through the analysis of oxygen uptake in the different communities. Although there was an indication that the oil had a depressing effect on the structure of both community types, it was not clear which species were most affected by the treatment. Individual comparisons between the two differently-structured treated communities and their controls were undertaken.

Abstract The genus Pteronia consists of approximately 80 species which are widely distributed in southern Africa. For hundreds of years the indigenous people of southern Africa have turned to the earth in order to provide healing for their people. The genus Pteronia has been amongst the first species to be used by the San and Khoi-San people for treating infections and stomach ailments. Ten species were selected for the purpose of this report. The essential oils were isolated by using a Clevenger-type apparatus while the non-volatiles were extracted with acetone and methanol. The essential oils and extracts were assessed for antimicrobial activity. The disc diffusion assays included three Gram-negative bacteria; Escherichia coli, Yersinia enterocolitica and Klebsiella pneumoniae, three Gram-positive bacteria; Staphylococcus aureus, Bacillus subtilis and Bacillus cereus as well as one yeast; Candida albicans. Results indicated that the species were primarily active against Gram-positive organisms. The minimum inhibitory concentration of the ten most active species (essential oils and extracts) were determined using the microdilution method. The most promising activity was noted for P. fasiculata which had a MIC of 0.22 mg/ml against S. aureus, 0.39 mg/ml against B. cereus and 2.08 mg/ml against B. subtilis. The essential oils analysis by GC/MS revealed two chemotypes. In Pteronia pallens, P. empetrifolia and P. flexicaulis rare compounds, such as presilphiperfolol-7-ene, 7-α-(H)-silphiperfol-5-ene, 7-β-(H)-silphiperfol-5-ene, α-campholene aldehyde, silphiperfol-5-ene, camaroonan-7-α-ol, silphiperfol-7- β -ol, presilphiperfolan-9- α -ol and presilphiperfolan-8-ol (a major compound in Pteronia pallens) were recorded. A cluster analysis of the essential oil data indicated that individual collections of P. camphorata within a population were tightly clustered. Similarly, P. pallens sampled from three different localities were also united in the cluster analysis. These results suggest minimal within and between population variations for some of the species studied.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (MSc (Paravet. Studies))--University of Pretoria, 2007. / Includes bibliographical references. Also available as hard copy.

Made available in DSpace on 2014-06-11T19:25:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-26Bitstream added on 2014-06-13T20:32:57Z : No. of bitstreams: 1 vieira_ld_me_botib.pdf: 650379 bytes, checksum: 2e951ffd593a61538c5b43bfddd72a7a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As úlceras pépticas são lesões provocadas pelo desequilíbrio entre fatores lesivos e protetores das mucosas gástrica e duodenal. Existe um grande número de plantas que são empregadas popularmente para o tratamento deste tipo de doença. Com este trabalho, pretende-se contribuir para a compreensão da ação farmacológica dos extratos de duas dessas plantas: a Alchornea glandulosa e a Davilla elliptica, assim como a Davilla nitida, que não é empregada na etnofarmacologia, mas pertence ao mesmo gênero de plantas com a função gastroprotetora. Neste sentido, foi realizada uma análise da composição multielementar destes compostos utilizando a técnica analítica de fluorescência de raios-X por reflexão total (TXRF). Foram analisadas, também, amostras de mucosas gástricas de ratos tratados com estes extratos fitoterápicos e que tiveram úlceras pépticas induzidas por dois protocolos: indução por etanol ou indução por Indometacina, uma droga anti-inflamatória não esteroidal (DAINE). As análises exploratórias e qualitativas foram efetuadas no Laboratório de Instrumentação Nuclear do Centro de Energia Nuclear na Agricultura (CENA/USP). A determinação das concentrações dos elementos P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br e Rb foi efetuada no Laboratório Nacional de Luz Síncrotron (LNLS) / Peptic ulcers are lesions caused by the disequilibrium between harmful and protective factors of gastric and duodenal mucosa. There are several plants that are commonly used for the treatment of this disease. The purpose of this work is contribute for the comprehension of the pharmacological action of extracts of two types of these plants: Alchornea glandulosa and Davilla elliptica, as Davilla nitida, which is not used in the ethnopharmocology, but it belongs to the same genus of plants, with gastroprotective activity. So, we have done an analysis of the multielemental composition of these compounds using the analytical technique of total reflection X-ray fluorescence (TXRF). We also analyzed samples of gastric mucosa of rats treated with herbal extracts, which had peptic ulcers induced by two protocols: induction by ethanol or by indomethacin, a non-steroidal anti-inflammatory drug (NSAID). The exploratory and qualitative analyzes were performed at the Nuclear Instrumentation Laboratory of the Brazilian Center for Nuclear Energy and Agriculture (CENA / USP). The concentrations of elements P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br and Rb were determinated at the Brazilian Synchrotron Light Laboratory (LNLS)

Combretum species are used in many cultures in folk medicine for treatment of microbial infections and several inflammatory conditions (abdominal pains, headache and toothache). There are two possible mechanisms to explain the use of plants extracts to treat microbial infections. A direct effect involves the action of active agents in the extracts on the microorganism tested and the indirect effect involves the stimulation of the host immune system to overcome the effects of microorganisms via the host immune system. Traditional healers use mainly aqueous extracts and in all Combretaceae we have studied, these extracts had hardly any in vitro antibacterial activity. A search of the literature confirmed our observations, aqueous plants extracts of many plant species usually have very little direct in vitro antimicrobial activity. One would expect that aqueous extracts would have higher anti-oxidant activities and may stimulate the immune system of patients thereby combating the infection indirectly. This possibility prompted the investigation of the antioxidant potential of more polar extracts of Combretum species. Methanol extracts of leaves of ten different Combretum species were evaluated for qualitative antioxidant activity by spraying TLC chromatograms of leaf extracts with 2, 2-diphenyl-1-picrylhydrazyl (DPPH). Compounds with anti-oxidant activity bleached the purple colour. Leaf extracts of Combretum apiculatum subspp apiculatumhad the most antioxidant compounds. This species was consequently selected for further examination. Anti-oxidant directed fractionation of the leaf extracts of C. apiculatum led to the isolation of four antioxidant compounds from ethyl acetate and butanol soluble fractions. The structures of the compounds were determined by spectral analyses (1H-NMR, 13C-NMR and MS) and identified as cardamomin (1), pinocembrin (2), quercetrin (3) and kaempferol (4). These compounds occur commonly in plant extracts, but the anti-oxidant activities of all these compounds were not known previously. In a quantitative antioxidant assay using DPPH with L-ascorbic acid as positive control, the more polar fractions (ethyl acetate and butanol) obtained by solvent-solvent fractionation had the highest activity among the extracts with EC50 values of 3.91 ± 0.02 and 2.44 ± 0.02 µg/mL respectively. Of the isolated compounds, quercetrin (3) and kaempferol (4) had strong antioxidant activity with EC50 values of 11.81 ± 85 and 47.36 ± 0.03 µM respectively. Cardamomin (1) and pinocembrin (2) did not have strong activity as these compounds could not scavenge 50% of the DPPH radical at the highest concentration (200 µM) tested. L-ascorbic acid was used standard antioxidant agent (EC50 = 13.37 ± 0.20 µM or 2.35 µg/mL). The antioxidant activity of the isolated compounds supported structure-activity relationships developed by other authors. The cytotoxicity of cardimonin and pinocembrim was evaluated using MTT assay with, berberine as positive control and DMSO as negative control. At higher concentrations than 50 µg/ml of cardimomin or pinocembrin the cells were not viable. Cardimomin was more toxic to the cells (LC50 of 1.97 µg/ml) than pinocembrin (LC50 of 29.47 µg/ml) and even the positive control, berberine (LC50 of 12.35 µg/ml). The presence of these antioxidants could provide a rationale for the ethnomedicinal use of this species for the treatment of inflammatory conditions in traditional medicine. It appears that the antimicrobial activity of aqueous plant extracts may be related to the antioxidant activity leading to a stimulated immune system rather than antimicrobial activity per se Because the crude polar extract had an antioxidant activity half that of L ascorbic acid, the rationale for using these plants by traditional healers becomes clear. The toxicity of cardomomin is a warning that the safety of these extracts should be evaluated in in vivo assays. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2007. / Paraclinical Sciences / unrestricted

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