Browsing by Author "Standley, Lauren"

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    Natural bio-antimutagenic activity of rooibos tea (Aspalathus linearis) as expressed by the Ames, Toxi-Chromo and SOS-Chromo tests
    (Stellenbosch : Stellenbosch University, 1999-03) Standley, Lauren; Britz, T. J.; Gelderblom, W. C. A.; Joubert, E.; Manley, M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH 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.