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dc.contributor.advisorPretorius, J. C.
dc.contributor.advisorPotgieter, G. P.
dc.contributor.authorCraven, Pieter
dc.date.accessioned2017-11-01T10:21:22Z
dc.date.available2017-11-01T10:21:22Z
dc.date.issued2003
dc.identifier.urihttp://hdl.handle.net/11660/7382
dc.description.abstractEnglish: Over the past number of years a renewed interest in the search for natural alternative products, with the aim to replace existing synthetic antimicrobial, herbicidal and pesticidal chemicals in organic crop production systems, was shown. Eucomis autumnalis, a medicinal plant found in South Africa, was used in this study to determine the biostimulatory and antimicrobial properties of a crude bulb extract as well as to evaluate the potential to develop a natural product from this plant. Preliminary screening procedures showed that the crude bulb extract possessed no biostimulatory, but indeed antimicrobial properties. After confirming the in vitro antifungal properties of the crude extract on a number of fungal pathogens, its in vivo activity against Mycosphaerella pinodes, causing Ascochyta blight on peas (Pisum sativum), was also confirmed. Using pea leaves, it was also shown that the crude bulb extract had no phytotoxic effect on the plant tissue even at the highest concentration applied. The collective in vitro and in vivo data obtained supplied the rationale for attempting to isolate and purify the active substance(s) responsible for the antifungal activity. By means of activity directed liquid-liquid extraction, using a series of organic solvents with increasing polarity, most of the antifungal activity was contained in a diethyl ether extractant. Column chromatographic separation of compounds in the active diethyl ether extractant yielded ten combined fractions of which only one showed significant anti-fungal activity against the test organism Sclerotium rolfsii. Subsequently, six active components were isolated from the latter fraction by means of preparative TLC and the chemical groups to which they belonged identified using standard colouring reagents as well as fluorescence under UV light. Due to some compounds having similar Rf-values and tested positive for more than one chemical group, it was clear that all in this fraction were not separated in pure form. However, all active compounds in this fraction tested positive for flavonoids, strongly indicating the presence of this chemical group. Flavonoids are known for their strong antifungal properties. It was concluded from this study that the bulbs of E. autumnalis possess significant antifungal activity to warrant a further investigation into the possibility to utilize this plant in developing a natural fungicide with application potential in agriculture. However, purification of the active substance(s) as well as the elucidation of its(their) molecular structure(s) will be important in order to investigate a possible mechanism of action.en_ZA
dc.description.abstractAfrikaans: Oor die afgelope tien jaar was daar ‘n oplewing in die soeke na natuurlike alternatiewe produkte om bestaande sintetiese antimikrobiese, onkruiddodende en insekdodende middels in organiese plantproduksie stelsels te vervang. Eucomis autumnalis, ‘n medisinale plant wat weidverspreid in Suid Afrika voorkom, is in hierdie studie gebruik om vas te stel of daar enige biostimulerende of antimikrobiese eienskappe in ’n ru-ekstrak van die bolle voorgekom het asook om die potensiaal vir die plant om in ’n natuurlike produk ontwikkel te word, te evalueer. ’n Voorlopige studie het aangedui dat die ru-ekstrak oor geen biostimulerende eienskappe beskik nie maar wel oor betekenisvolle antimikrobiese eienskappe. Nadat die in vitro antifungale eienskap van die ru-ekstrak teen ’n verskeidenheid van plantpatogeniese swamme bevestig is, is die in vivo aktiwiteit teen Mycosphaerella pinodes, wat swartroes op ertjies (Pisum sativum) veroorsaak, ook bevestig. Daar is ook aangetoon dat die ru bol-ekstrak, selfs teen die hoogste konsentrasie toegedien, geen fitotoksiese effek op die blaarweefsel van ertjies gehad het nie. Die kollektiewe in vitro en in vivo data wat bekom is het die rasionaal verskaf vir ’n verdere poging om die aktiewe antifungale komponent(e) te isoleer en te suiwer. Deur aktiwiteitsgerigte vloeistof-vloeistof ekstraksie, met behulp van ’n reeks organiese oplosmiddels met toenemende polariteit, is die meeste antifungale aktiwiteit in diëtieleter gekonsentreer. Kolom chromatografiese skeiding van die komponente in die aktiewe diëtieleter ekstrak het tien gekombineerde fraksies opgelewer waarvan slegs een betekenisvolle antifungale aktiwiteit teen die toetsorganisme, Sclerotium rolfsii, getoon het. Ses aktiewe komponente is voorts deur middel van preparatiewe dunlaagchromatografie uit laasgenoemde fraksie geïsoleer en die chemiese groepe waaraan hulle behoort is met behulp van standaard kleurreagense asook fluoressensie onder UV-lig geïdentifiseer. Aangesien die Rf-waardes van sommige komponente baie ooreengestem het en sommiges positief getoets het vir meer as een komponent, was dit duidelik dat aktiewe bestanddele nie in suiwer vorm bekom was nie. Maar, alle fraksies het positief getoets vir flavonoïede wat sterk gedui het op die teenwoordigheid van hierdie chemiese groep. Flavonoïede is bekend vir hul sterk antifungale eienskappe. Deur hierdie studie is tot die gevolgtrekking gekom dat die bolle van E. autumnalis oor genoegsame antifungale aktiwiteit beskik om ‘n verdere studie te onderneem ten einde die moontlikheid om die plant te gebruik vir die ontwikkeling van ‘n natuurlike fungisied, wat in die landboupraktyk toegepas kan word, te ondersoek. Daar word ook aanbeveel dat verdere suiwering van die aktiewe komponent(e) asook vasstelling van die chemiese struktuur daarvan uitgevoer moet word ten einde moontlike aksiemeganismes te ontsyfer.en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectNatural productsen_ZA
dc.subjectAlternative cropsen_ZA
dc.subjectEucomis autumnalisen_ZA
dc.subjectAntifungal propertiesen_ZA
dc.subjectActive ingredientsen_ZA
dc.subjectFlavonoidsen_ZA
dc.subjectNatural products in agricultureen_ZA
dc.subjectFungal diseases of plantsen_ZA
dc.subjectAnti-infective agentsen_ZA
dc.subjectMedicinal plants -- Diseases and pestsen_ZA
dc.subjectDissertation (M.Sc. Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2003en_ZA
dc.titleAn investigation into the biocatalytic and antimicrobial properties of Eucomis autumnalis Mill. bulbsen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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