Natural bio-antimutagenic activity of rooibos tea (Aspalathus linearis) as expressed by the Ames, Toxi-Chromo and SOS-Chromo tests

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dc.contributor.advisorBritz, T. J.en_ZA
dc.contributor.advisorGelderblom, W. C. A.en_ZA
dc.contributor.advisorJoubert, E.en_ZA
dc.contributor.advisorManley, M.en_ZA
dc.contributor.authorStandley, Laurenen_ZA
dc.contributor.otherStellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
dc.date.accessioned2012-08-27T11:34:27Z
dc.date.available2012-08-27T11:34:27Z
dc.date.issued1999-03
dc.descriptionThesis (M.Sc. in Food Science) -- University of Stellenbosch, 1999.
dc.description.abstractENGLISH SUMMARY: Rooibos tea (Aspalathus linear is), an indigenous fynbos plant, is cultivated in the Clanwilliam area of the Western Cape and has become increasingly popular due to its alleged health properties. The confirmation of antimutagenic potential in Rooibos tea is important and research on its chemo-preventive properties would substantiate it as a health promoting agent. The antimutagenic properties of fermented and unfermented Rooibos were determined and compared to that of green and black teas (Camellia sinensis). The Ames test, using Salmonella typhimurium TA 98 and the mutagen 2- acetylaminofluorene (2-AAF), was performed on the ethyl acetate and water-soluble fractions of the four tea extracts. The green tea had the strongest antimutagenic potential (67.6% inhibition), followed by the unfermented Rooibos tea (59.1 % inhibition). The fermented Rooibos (47.3% inhibition) and black (46.5% inhibition) teas showed the lowest antimutagenic potential. The ethyl acetate extracts had the stronger antimutagenic potential, indicating that most compounds responsible for the teas antimutagenic potential are probably found in this extract. At a standardised total polyphenol content the green (75.5% inhibition) and unfermented Rooibos (75.1 % inhibition) teas had very similar antimutagenic potentials. The fermented Rooibos (73.0% inhibition) had a higher antimutagenic potential than the black tea (70.5% inhibition). Ames tests done on samples from the five processing stages in the manufacture of Rooibos tea revealed that processing does cause a reduction in the antimutagenic potential of the tea. The major decrease in antimutagenic potential occurred after the fermentation stage (P<0.05). Since, aspalathin is one of the major polyphenols found in Rooibos tea, the Ames test was performed using a crude aspalathin fraction to determine if polyphenols or more specifically aspalathin, are responsible for the antimutagenic properties in Rooibos tea. The Ames test revealed that the aspalathin fraction had antimutagenic potential that, on average, was 5 - 15% lower when compared to the antimutagenic potential in Rooibos tea water-soluble extracts. The results of the Ames tests performed, using S. typhimurium T A 98, on random Rooibos tea samples from five commercial retailers revealed that the processing of Rooibos tea produces tea with fairly uniform antimutagenic potential. The SOS-Chromotest, to test for genotoxicity and the Toxi-Chromotest, to test for toxicity of the four tea extracts (fermented Rooibos, unfermented Rooibos, green and black tea), were also performed. These tests are based on mutant strains of Escherichia coli and depend on a colour reaction to determine results of the tests. Colour profiles from the SOS-Chromotest were too faint to determine results from, whereas the Toxi-Chromotest colour profiles indicated that the four tea extracts probably had a toxic effect on the mutant bacteria. Further investigations were conducted to try and explain these inconclusive results and growth studies to determine if the tea was having an-inhibitory effect on the growth of the bacteria were performed on the bacterial tester strains and a standard E. coli culture (ATCC 58). The resulting data indicated that fermented and unfermented Rooibos had a very strong inhibitory effect on the growth of the bacteria while the green and black teas had lower inhibitory effects on the growth of the bacteria.
dc.description.abstractAFRIKAANSE OPSOMMING: Rooibostee (Aspalathus linearis), 'n inheemse fynbosplant, word in die Wes-Kaap in die Clanwilliam omgewing verbou en het in gewildheid begin toeneern weens die beweerde gesondheidseienskappe daarvan. Die bevestiging van die antimutageniese potensiaal van Rooibostee is belangrik en navorsing op die chemo-voorkomende eienskappe daarvan behoort dit te onderskei as 'n drankie wat die gesondheid sal bevoordeel. Die antimutageniese eienskappe van gefermenteerde- en ongefermenteerde Rooibostee is bepaal en vergelyk met die van groen- en swarttee (Camellia sinensis), onderskeidelik. Die etielasetaat- en wateroplosbare fraksies van die vier tee ekstrakte is, onderskeidelik, getoets volgens die Amesmetode en Salmonella typhimurium TA 98 en die mutageen, 2-asetielaminofloureen (2-AAF), is gebruik. Die hoogste antimutageniese aktiwiteit is waargeneem met die groentee (67.6% inhibisie) gevolg deur die ongefermenteerde Rooibostee (59.1 % inhibisie). Die gefermenteerde Rooibostee (47.3% inhibisie)en die swarttee (46.5% inhibisie) het die laagste antimutagenisiteit getoon. Die hoogste antimutageniese potensiaal is waargeneem met die etielasetaatfraksie, wat daarop dui dat meeste van die komponente verantwoordelik vir die tee se antimutagenisiteit moontlik in hierdie ekstrak voorkom. Die ongefermenteerde Rooibos- en groentee wateroplosbare fraksies het dieselfde antimutagenisiese aktiwiteit getoon, indien gestandardiseer tot 'n standaard totale polifenolinhoud, terwyl die gefermenteerde Rooibostee 'n sterker antimutagenisiese aktiwiteit as swarttee getoon het. Die Amestoets wat op monsters van onderskeidelik vyf prosesseringstappe van Rooibostee uitgevoer is, het daarop gedui dat prosessering die antimutageniese potensiaal van die tee verlaag. Resultate het bevestig dat die grootste verlaging in antimutageniese potensiaal tydens die fermentasie proses plaasgevind het. Aangesien aspalatien een van die hoof polifenole in Rooibostee is, is die Amestoets uitgevoer op 'n ru-fraksie van aspalatien om te bepaal of polifenole of, meer spesifiek, aspalatien verantwoordelik is vir die antimutagenisiteit van Rooibostee. Die Amestoets het bewys dat die aspalatienfraksie antimutageniese potential het, wat gemiddeld 5 - 15% laer was as die van die wateroplosbare verbindings in Rooibostee. Resultate van die Amestoets op kommersiele Rooibostee monsters van vyf verskillende kleinhandelaars het aangedui dat die vervaardigingsproses van Rooibostee, 'n produk met 'n redelike eenvormige antimutageniese potensiaal lewer. Die SOS-Chromotoets en die Toxi-Chromotoets, wat onderskeidelik vir genotoksisiteit en vir toksisiteit toets, is op die vier wateroplosbare tee ekstrakte, naamlik ongefermenteerde Rooibos-, gefermenteerde Rooibos-, groen- en swarttee uitgevoer. Hierdie toetse is gebaseer op spesifieke mutante rasse van Escherichia coli en die resultate word bepaal deur kleurreaksies. Die SOS-Chromotoets kleurprofiel het swak ontwikkel, terwyl die kleurprofiele van die Toxi-Chromotoets aangedui het dat die tee ekstrakte moontlik 'n toksiese effek op die mutante bakteriee gehad het. Verdere ondersoeke is uitgevoer om hierdie onduidelike resultate te probeer verduidelik en groei studies, om te bepaal of die tee 'n inhiberende effek op die bakteriee het, is ook gedoen. Die resultate het aangedui dat ongefermenteerde- en gefermenteerde Rooibostee 'n baie sterk inhiberende effek op die groei van die bakteriee het, terwyl die groen- en swarttee 'n kleiner inhiberende effek op die groei van die bakteriee gehad het.
dc.description.versionMaster
dc.format.extent110 pages : ill.
dc.identifier.urihttp://hdl.handle.net/10019.1/51348
dc.language.isoen_ZA
dc.publisherStellenbosch : Stellenbosch University
dc.rights.holderStellenbosch University
dc.subjectRooibos tea -- Processingen_ZA
dc.subjectRooibos teaen_ZA
dc.subjectRooibos tea -- Health aspects -- Testingen_ZA
dc.subjectAntimutagens -- Testingen_ZA
dc.subjectGreen tea -- Testingen_ZA
dc.subjectTea -- Testingen_ZA
dc.subjectBeverages -- Testingen_ZA
dc.subjectDissertations -- Food scienceen_ZA
dc.titleNatural bio-antimutagenic activity of rooibos tea (Aspalathus linearis) as expressed by the Ames, Toxi-Chromo and SOS-Chromo testsen_ZA
dc.typeThesisen_ZA
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