Thesis (MSc Food Sc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT:Aspalafhus linearis is an indigenous fynbos plant cultivated in the Clanwilliam area of the Western Cape, South Africa. The rooibos tea that is prepared from this plant, has become popular worldwide mainly due to the alleged health properties. Studies on the anti-microbial properties of green, black and oolong teas have shown that these teas have strong anti-microbial activity against a wide range of microbes. No studies have been done on the anti-microbial activity of rooibos tea and the aim of this study was to determine what impact rooibos tea extracts would have on the growth of different food spoilage and potential pathogenic microbes. Water and ethyl acetate extracts of fermented and unfermented rooibos tea were used to determine the inhibitory effect on the growth of an Escherichia coli strain. The E. coli culture was grown in tea-MRS with either added fermented or unfermented rooibos tea extracts. Both the water and ethyl acetate extracts showed a strong inhibitory effect against the E. coli strain in that there was a decrease in the final bacterial cell density (Nmax)(from 0.59 00 to 0.25 00) and the maximum specific growth rate (~max)(from 1.12 h-1 to 0.20 h-1) and an increase in the doubling time (~) (from 0.59 h to 1.80 h) and lag time (tlag)(from 4.81 h to 6.60 h) as the concentration of the soluble solids of the tea extracts was increased from 0.5 to 5.0 g.r1 . Furthermore, it was found that the fermented rooibos tea had a much stronger inhibitory effect (69% decrease in growth at 5.0 g.r1 soluble solids) compared to the unfermented rooibos tea extracts (35.1% decrease in growth at 5.0 g.r1 soluble solids). The resulting data indicated that rooibos tea had a very strong inhibitory effect on the growth of the E. coli strain. It was also found that the water extracts of rooibos tea showed a stronger inhibitory effect on the growth of the E. coli than the ethyl acetate extracts, indicating that the antimicrobial activity of rooibos tea is not exclusively due to the polyphenolic content - individual compounds. It was also determined that the rooibos tea water extracts showed a bacteriostatic action against the E. coli strain in that as soon as the tea is no longer part of the growth medium, the E. coli resumed a normal growth pattern. The data obtained showed that the inhibitory effect of rooibos tea water extracts (69% decrease in growth) against the growth of E. coli was more pronounced than that found when black tea water extracts (25.7% decrease in growth) at the same concentrations were used.Rooibos tea water extracts (0.5 - 5.0 g.r1) of fermented and unfermented tea were also used to determine the inhibitory effect on other food spoilage microbes and potential pathogens. Strains of Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces cerevisiae and Zygosaccharomyces rouxii were grown in the presence of fermented and unfermented rooibos tea water extracts. The effect that fermented rooibos tea had on the growth of all the microbes tested was in the following order: Staph. aureus (90.8% decrease in growth) > L. monocytogenes (89.2% decrease in growth) > Strep. mutans (84.1% decrease in growth) > B. cereus (80.3% decrease in growth) > Sacch. cerevisiae (77.7% decrease in growth) > E. coli (69.0% decrease in growth). The rooibos tea clearly had an inhibitory effect on the growth of all the microbes, with the exception of the Z. rouxii strain where the presence of the tea water extracts was found to enhance the growth. The inhibitory effect of rooibos tea on the growth of these microbes was shown by changes in the growth parameters with Nmax and IJmaxshowing decreases, while the ld and tlagincreased as the concentration of the tea soluble solids was increased. As with E. coli, the fermented rooibos tea water extracts showed the stronger inhibitory effect on the growth of the various microbes. The data obtained in this study suggests that rooibos tea is not effective as an anti-microbial agent against all yeast species, but will strongly retard the growth of specific Gram-positive and Gram-negative bacteria. As long as rooibos tea is present, strong anti-microbial activity will be observed at a cup of tea concentration of 2.5 g.r1 soluble solids. These results may be of value to support the health claims associated with rooibos tea and may in the future lead to the use of rooibos tea as a "natural" food preservative. / AFRIKAANSE OPSOMMING:Aspalathus linearis is 'n inheemse fynbosplant wat gekultiveer word in die Clanwilliam area van die Wes Kaap, Suid-Afrika. Rooibostee, wat gemaak word van hierdie plante, het baie gewild geword wereldwyd a.g.v. die gesondheidsaspekte van hierdie tee. Studies toon dat groen, swart en oolong tee sterk anti-mikrobiese aktiwiteit het teen 'n wye reeks mikrobes. Aangesien daar voorheen geen studies gedoen is op die anti-mikrobiese aktiwiteit van rooibostee nie, was die doel van hierdie studie om die effek van rooibostee te bepaal op die groei van verskillende voedselbederwers en potensiele patogeniese mikrobes. Water- en etielasetaat-ekstrakte van gefermenteerde en ongefermenteerde rooibos tee is gebruik om die inhiberende effek op die groei van Escherichia coli te bepaal. Escherichia coli is gegroei in tee-MRS met bygevoegde gefermenteerde of ongefermenteerde rooibostee-ekstrakte. Seide die water- en etielasetaatekstrakte van rooibostee het 'n sterk inhiberende effek gewys teen E. coli en dit word gestaaf deur 'n afname in die finale bakteriese seldigtheid (Nmax)(vanaf 0.59 00 tot 0.25 00) en die maksimum spesifieke groeitempo (lJmax) (vanaf 1.12 h-1 tot 0.20 h-1) en 'n toename in die verdubbelingstyd (~) (vanaf 0.59 h tot 1.80 h) en die sloerfase (tlag)(vanaf 4.81 h tot 6.60 h) 5005 wat die konsentrasie van oplosbare vastestowwe van die tee toeneem van 0.5 tot 5.0 g.r1 . Verder is daar gevind dat die gefermenteerde rooibostee 'n baie sterker inhiberende effek het (69% afname in groei by 5.0 g.r1 oplosbare vastestowwe) in vergelyking met die ongefermenteerde rooibostee-ekstrakte (35.1% afname in groei by 5.0 g.r1 oplosbare vastestowwe). Die resultate van die data dui aan dat rooibos tee 'n baie sterk inhiberende effek het op die groei van die E. coli spesie. Die waterekstrakte van rooibostee het 'n sterker inhibisie getoon teen die groei van E. coli as die etielasetaat-ekstrakte, wat aandui dat die anti-mikrobiese aktiwiteit van rooibostee nie eksklusief toegeskryf kan word aan die polifenoliese samestelling nie. Daar is ook gevind dat rooibostee water-ekstrakte 'n bakteriostatiese effek het teen E. coli, want sodra die tee ekstrakte nie meer teenwoordig is in die groeimedium nie, hervat E. coli normale groei. Die data wys ook dat die inhiberende effek van rooibostee water-ekstrakte (69.0% afname in goei) teen E. coli baie sterker is as die van swart tee water-ekstrakte (25.7% afname in groei) by dieselfde konsentrasies.Rooibostee water-ekstrakte (0.5 - 5.0 g.r1) van gefermenteerde en ongefermenteerde rooibostee is ook gebruik om die inhiberende effek te bepaal teen ander voedselbederwers en potensiele patogene. Spesies van Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces cerevisiae en Zygosaccharomyces rouxii is gegroei in die teenwoordigheid van gefermenteerde en ongefermenteerde rooibostee waterekstrakte. Die effek wat gefermenteerde rooibostee het op die groei van die getoetste mikrobes is 5005 volg: Staph. aureus (90.8% afname in groei) > L. monocytogenes (89.2% afname in groei) > Strep. mutans (84.1% afname in groei) > B. cereus (80.3% afname in groei) > Sacch. cerevisiae (77.7% afname in groei) > E. coli (69.0% afname in groei). Rooibostee het 'n duidelike inhiberende effek gehad teen al die organismes, behalwe teen Z. rouxii spes ie, waar die teenwoordigheid van rooibostee die groei van die organisme bevorder het. Die inhiberende effek van rooibostee teen die groei van hierdie mikrobes word ondersteun deur die groei parameters waar die Nmaxen IJmaxafgeneem het terwyl die ~ en tlagtoegeneem het 5005 wat die konsentrasie van die oplosbare vastestowwe toeneem. Die gefermenteerde rooibostee water-ekstrakte het ook 'n sterker inhiberende effek op die groei van die verskillende mikrobes net 5005 met E. coli. Die data wat verkry is van hierdie studie dui aan dat rooibostee nie effektief sal wees as 'n anti-mikrobiese middel teen aile gis spesies nie, maar dit sal die groei van spesifieke Gram-positiewe en Gram-negatiewe bakterie sterk vertraag. So lank as wat rooibostee teenwoordig is, sal sterk anti-mikrobiese aktiwiteit waargeneem word by 'n koppie-tee konsentrasie van 2.5 g.r1 oplosbare vastestowwe. Hierdie resultate kan help om die gesondheidseienskappe geassosieer met rooibostee te ondersteun en help om die gebruik van rooibostee as 'n "natuurlike" preserveermiddel te bevorder. dedicated to my parents

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This study describes: • the influence of a methanolic extract of unfermented Rooibos and five major Rooibos flavonoids, aspalathin, nothofagin, rutin, orientin and vitexin, on the activities of key adrenal steroidogenic enzymes - cytochrome P450 17β- hydroxylase/17,20-lyase (CYP17A1), 3β-hydroxysteroid dehydrogenase • the development of a novel UPLC-MS/MS method for the separation and quantification of 21 adrenal steroid metabolites; • the influence of Rooibos and aforementioned flavonoids on adrenal steroid hormone production in H295R cells - a human adrenal carcinoma cell line expressing the enzymes catalysing the production of mineralocorticoids, glucocorticoids and adrenal androgens, assayed under both basal (normal) and forskolin-stimulated (stressed) conditions; • the influence of Rooibos on the inter-conversion between cortisol and cortisone by 11βHSD1 and 11βHSD2 expressed in CHO-K1 cells; • the influence of Rooibos consumption on circulating steroid hormone levels and ratios in male Wistar rats; • the influence of Rooibos consumption on circulating steroid hormone levels and ratios in male and female human test subjects at risk for developing cardiovascular disease. (3βHSD2), cytochrome P450 21-hydroxylase (CYP21A2) and cytochrome P450 11β-hydroxylase (CYP11B1), expressed in non-steroidogenic COS-1 cells; / AFRIKAANSE OPSOMMING: Hierdie studie beskryf: • die invloed van metanoliese ekstrakte van ongefermenteerde Rooibos en vyf van die hoof flavonoïedverbindings in Rooibos, aspalatien, notofagien, rutien, oriëntien en viteksien, op die aktiwiteite van ensieme wat steroïedbiosintese in die bynier kataliseer – sitochroom P450 17α-hidroksilase/17,20-liase (CYP17A1), 3β-hidroksisteroïed dehidrogenase (3βHSD2), sitochroom P450 21-hidroksilase (CYP21A2) en sitochroom P450 11β-hidroksilase (CYP11B1), uitgedruk in nie-steroïed produserende COS-1 selle; • die ontwikkeling van ‘n geskikte UPLC-MS/MS metode vir die skeiding en kwantifisering van 21 steroïedmetaboliete in die bynier; • die invloed van Rooibos en die bg. flavonoïede op steroïedproduksie in H295R selle – ‘n menslike bynier kanker sellyn gekenmerk deur die ekspressie van die steroidogeniese ensieme wat die produksie van mineralokortikoïede, glukokortikoïede en bynierandrogene kataliseer, geanaliseer onder beide basale (normale) en forskoliengestimuleerde (gestresde) kondisies; • die invloed van Rooibos op die omeenskakeling tussen kortisol en kortisoon deur 11βHSD1 and 11βHSD2 in CHO-K1 selle; • die invloed van Rooibosinname op vlakke van sirkulerende steroïed hormone en relatiewe verhoudings in die bloed van manlike Wistarrotte; • die invloed van Rooibosinname op sirkulerende steroïed hormoon vlakke en relatiewe verhoudings in die bloed van mans en vrouens met ‘n hoë risiko vir die ontwikkeling van kardiovaskulêre siektes.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A comprehensive food frequency questionnaire (FFQ) was developed to assess the daily total flavonoid intake over the past fortnight within a 14-week intervention that consisted of four periods to determine the effect of rooibos consumption on oxidative stress in adults (n=40) at intermediate to high coronary heart disease (CHD) risk. Within the intervention the comprehensive FFQ validity (against six estimated dietary records and biomarkers), reproducibility (on administrations in the washout and control periods six weeks apart as these periods had similar flavonoid intake restrictions) and responsiveness (across the four intervention periods of changed dietary conditions) was evaluated. The baseline period dietary record and FFQ dietary sources found to contribute most to the participants’ daily total flavonoid intake, considering the percentage contribution, and the between-person variation in intake, considering the stepwise multiple regression analysis, formed the food list of the resultant abbreviated FFQ. The validity, reproducibility and responsiveness of the latter were also evaluated within the intervention and its validity (against dietary records) and reproducibility (on re-administration two weeks apart) in an additional group (n=90) being at low and intermediate CHD risk to evaluate its external strength. The validity and reproducibility evaluations of the comprehensive and abbreviated FFQs in the intervention and abbreviated FFQ within the additional group comprised paired difference tests (to establish the ability to estimate group intakes), correlation coefficients (to establish the ability to rank individual participants), category agreement and gross misclassification next to the weighted kappa statistic (to establish the ability to classify the participants into tertiles and quintiles of intake) and Bland-Altman plots (as representation of the limits of agreement between the two dietary assessment methods). Correlation coefficients were also used for biomarker validity evaluations in the baseline period. The repeated measures analysis of variance (ANOVA) (Bonferroni correction) was used for the responsiveness evaluations of the comprehensive and abbreviated FFQs across the intervention periods alongside that of the biomarkers as evidence for the changed dietary conditions. The study demonstrated that the comprehensive FFQ could be modified to a format with a brief food list as few items contributed appreciably to the total flavonoid intake and of which most also contributed to the between-person intake variability. The comprehensive and moreover the abbreviated FFQ in the validity evaluations provided sufficiently accurate daily total flavonoid intake estimates. They could determine the intake at group level in correspondence with that of the dietary records. The participant intakes could additionally be categorized and in particular ranked greatly alike to the dietary record intakes. The Bland-Altman plots revealed proportional bias regarding overestimation at the higher intake level. The reproducibility also appeared to be greatly satisfactory although seasonal fruit exclusions from the abbreviated FFQ food list may hamper its repeated administration. Both FFQs also confirmed the changed total flavonoid intakes across the intervention periods in relation to changes in the expected direction concerning the plasma total polyphenol, conjugated diene and thiobarbituric acid reactive substance concentrations. / AFRIKAANSE OPSOMMING: ‘n Omvattende voedsel frekwensie vraelys (VFV) is ontwikkel om die daaglikse totale flavonoïed inname oor twee agtereenvolgende weke te beraam te midde van ‘n 14-week intervensie. Die intervensie het uit vier periodes bestaan wat die effek van rooibosinname op oksidatiewe stres in volwassenes (n=40), met ‘n intermediêre tot hoë koronêre hartsiekte (KHS) risiko, bepaal het. Binne die intervensie is die geldigheid (teen ses geskatte dieetrekords en biochemiese merkers), herhaalbaarheid (op aanwending ses weke uitmekaar in die uitwas en kontrole intervensie periodes met dieselfde flavonoïed inname bepalings) en waarneembaarheid (oor vier intervensie periodes van veranderde dieet bepalings) van die omvattende VFV geëvalueer. Die dieetbronne in die basislyn periode dieetrekords en vraelyste wat die meeste tot die deelnemers se daaglikse totale flavonoïed inname (baseer op die persentasie bydrae) en die tussen-persoon variasie in inname (baseer op die stapsgewyse meervuldige regressie analise) bygedra het, het die voedsellys van die voortvloeiende verkorte VFV gevorm. Die geldigheid, herhaalbaarheid en waarneembaarheid van dié VFV is binne die intervensie geëvalueer en die geldigheid (teen dieetrekords) en herhaalbaarheid (heradministrasie twee weke later) daarvan in ‘n verdere groep (n=90) met lae en intermediêre KHS risiko as evaluasie van die eksterne vermoë van die VFV. Die geldigheid en herhaalbaarheid evaluasies van die omvattende en verkorte VFV in die intervensie en die verkorte VFV in die verdere groep het bestaan uit gepaarde verskil toetse (bepaling van die groepinname skattingsvermoë), korrelasie koëffisiënte (bepaling van individuele deelnemer rangorde skattingsvermoë), kategorie ooreenstemming en erge wanklassifikasie naas die aangepaste kappa statistiek (bepaling van die vermoë om die deelnemer innames in derdes en vyfdes te klassifiseer) en die Bland-Altman karterings (verteenwoordiging van ooreenstemmingslimiete tussen die twee dieetinname metodes). Korrelasie koëffisiënte is ook gebruik vir biochemiese merker geldigheid evaluasies in die basislyn periode. Die herhaalde metings analise van variansie (ANOVA) (Bonferroni regstelling) is gebruik om die waarneembaarheid evaluasies van die omvattende en verkorte VFV oor die intervensie periodes naas dit van die biochemiese merkers te evalueer as bewys van die veranderde dieet bepalings. Die studie het aangedui dat die omvattende VFV gewysig kon word tot ‘n formaat met ‘n verkorte voedsellys omdat slegs ‘n aantal items merkbaar tot die totale flavonoïed inname bygedra het en die meeste hiervan ook tot die tussen-persoon variasie in inname. Die omvattende en die verkorte VFV het in die geldigheid evaluasies daarvan voldoende akkurate daaglikse totale flavonoïed inname skattings opgelewer omdat groep innames bepaal kon word in ooreenstemming met dit verkry van die dieetrekords en die deelnemer innames bykomend kategoriseer en in besonder grootliks eenders rangeer kon word as met hul dieetrekord innames. ‘n Proporsionele oorskatting by die hoër inname vlakke is wel vir al twee getoon in die Bland-Altman karterings. Die herhaalbaarheid was ook grootliks aanvaarbaar, alhoewel seisoenale vrugte uitsluitings in die verkorte VFV voedsellys die heruitvoering kan bemoeilik. Al twee vraelyste kon ook die veranderinge in die daaglikse totale flavonoïed inname oor die intervensie periodes bevestig in ooreenstemming met veranderinge in die verwagte rigting van die plasma totale polifenool, konjugaat diëne en tiobarbituursuur reaktiewe stof konsentrasies.

Thesis (MTech (Consumer Science: Food and Nutrition))--Cape Peninsula University of Technology, 2016. / Background: The different types and forms of rooibos and the ways in which it is prepared and flavoured for consumption influences its total polyphenol content and total antioxidant capacity (TAC) and hence depends on its consumer practices. Design: Phase 1 of the study entailed the selection and preparation of different rooibos types and forms; rooibos brewed for different times; and with different household and commercially added flavourings to determine the total polyphenol content, TAC, flavonol and flavanol content; and subsequent identification of the optimal cup of rooibos based on the first two biochemical parameters. For Phase 2 a questionnaire was used to obtain information on the profile of the adult rooibos herbal tea consumer, as well as of those consuming the optimal cup of rooibos. Results: The following prepared rooibos samples delivered the higher biochemical parameter content: green / unfermented (type representative); green / unfermented leaves and powdered extract (form representatives); that brewed for 10 minutes or longer; and those with added honey. The optimal cup of rooibos was identified as the one brewed for 10 minutes or longer. The older respondents and those with a lower level of education consumed a higher daily amount of rooibos (p < 0.05) and those who brewed rooibos in a teapot consumed the optimal cup (p < 0.05). However, very few respondents consumed the advised number of cups per day (< 1%) and the identified optimal cup (15.9%). Conclusions: Rooibos consumers in this study did not consume it in sufficient amounts and did not brew it for long enough to fully gain from its attributed health benefits.

Magister Scientiae - MSc / Background: Early postnatal radiation exposure from environmental, diagnostic or therapeutic sources is potentially deleterious to the developing nervous system resulting in oxidative stress, structural damage, altered neurochemistry, DNA damage, inflammatory stresses as well as correlating cognitive impairment during adult life. Numerous studies in literature have investigated the radioprotective effects of medicinal plants and beverages. However, only a few studies have focused on the radioprotective effects of rooibos, an indigenous South African herbal tea, well known for its many acclaimed health benefits. Aims: This study was done to investigate the diverse radioprotective potential of fermented Rooibos herbal tea (FRHT) consumed ad libitum by pregnant rats on the adult offspring rats exposed to a once-off 6 Gy dose of gamma irradiation on postnatal day 3. Methods: Twenty-four (24) adult female rats were equally divided into four groups (6 per group) as control (NS), radiation (X), tea (RT) and their combination. On PND 30, offspring rats were subjected to neurobehavioural assessment for open field and novel object recognition parameters and later sacrificed, the brain tissues removed and processed for histological, immunohistochemical and neurochemical analyses, using standard techniques. Results: Pre-treatment with FRHT showed overall protection against radiation-induced distortions in offspring rats by significantly improving exploratory activity, the frequency of central square entry, rearing episodes, cumulative freezing time and memory retention as indicated by a relatively higher recognition index. FRHT was also found to significantly improve the antioxidant defence mechanisms in the offspring rats by reversing lowered FRAP levels, increasing superoxide dismutase and catalase enzyme activities and reducing lipid peroxidation. Histological and immunohistochemical analyses showed that morphological alterations were generally attenuated in the RTX group and the high number of caspase-3 and Glial fibrillary acidic protein (GFAP)-positive cells was significantly reduced, indicating protective effects against apoptosis and gliosis. Conclusion: Taken together, our findings tend to suggest that the potential radioprotective effects of FRHT are multimodal, possibly executed through the anti-apoptotic, antioxidative, anti-gliosis and other mechanisms, as observed in this study, and this is often attributed to the high polyphenol content in Rooibos tea.

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2008. / Bibliography: leaves 66-79. Also available online.

Thesis (MSc Food Sc) (Food Science)--Stellenbosch University, 2008. / The change in aspalathin, iso-orientin, orientin and total polyphenol (TP) content of a commercially produced fermented rooibos (FR) extract was monitored throughout production. Particular attention was paid to the effect of spray-drying on FR and unfermented rooibos (UR) extracts. The quality of commercial, South African rooibos iced teas made with FR extract was also investigated with respect to the aforementioned parameters. Subsequently, the effect of heating and storage on the phenolic composition and colour of experimental iced teas containing respectively FR, UR and nano emulsified unfermented rooibos (NEUR) extracts was investigated. The combined effect of pH (pH 3-7) and storage (5, 30 and 40ºC), as well as high (660 mg/L, 0-7 days at 30ºC; UR only) and low (0.5 mg/L) concentrations of H2O2, was determined on reconstituted FR, UR and NEUR extracts. Finally, eight rooibos iced teas (four variants; unflavoured and lemon-flavoured) were analysed for plant-like, hay-like, rooibos and lemon flavour, as well as astringency, using descriptive sensory analysis. The degree of consumer preference of the flavoured variants was determined using the nine point hedonic scale. In all cases, changes in individual flavonoid content were quantified using HPLC. The TP content of the iced teas and commercial extracts was determined using the Folin-Ciocalteu assay. Browning of the iced teas and reconstituted extracts was monitored spectrophotometrically (420 nm). Aspalathin, iso-orientin and orientin were found to be present after all stages of the FR extract production process. Spray-drying, specifically, also did not reduce the content of these flavonoids, or the TP content, in FR and UR extracts. Despite the relatively good retention during the heating and storage of experimental rooibos iced teas, these flavonoids were either absent or present at extremely low levels in commercial iced teas. The latter suggested that either extremely low quantities of extract, no extract at all or extracts of poor quality, were used for the production of the analysed iced teas. Increased degradation was generally observed for sterilisation treatments compared to pasteurisation whilst losses during storage increased with time. The presence of citric acid, due to its pH-lowering effect, and ascorbic acid, due to its antioxidant activity, was integral to the retention of aspalathin, iso-orientin and orientin during heating, but less so during storage. The UR iced teas generally performed better than their FR counterparts, however, NEUR iced teas exhibited the greatest retention of the aforementioned flavonoids. Heating and storage resulted in browning of most iced teas, whilst the TP content increased slightly or remained unchanged. Phenolic retention in FR and UR extracts decreased with increasing pH and temperature, with concomitant browning. However, between pH 5 and 7, the stability of aspalathin was superior in the NEUR extract formulation. The latter also greatly resisted absorbance changes at pH 3 and 4, despite a loss of aspalathin. The phenolic content of UR extract was immediately reduced by high a concentration of H2O2, however, no significant (P≥0.05) changes in absorbance were detected, suggesting the formation of intermediate, colourless oxidation products. Formulations containing ascorbic acid experienced the greatest reductions. This was attributed to the iron reducing ability of this compound, as reduced iron accelerates the rate of the Fenton reaction. At low levels of H2O2, only the FR extract exhibited a loss of phenolic compounds. The level of iron in this extract was the highest. Despite having the greatest aspalathin and total flavonoid content, lemon flavoured unfermented rooibos iced tea (UF/LEMON) was disliked by consumers. Preference was directed away from the plant-like characteristic of this tea and towards rooibos flavour, characteristic of fermented rooibos iced tea. Iced tea comprising both FR and NEUR extract produced a product that 77% of consumers rated positively. Its slight hay-like flavour did not significantly (P≥0.05) reduce the liking of this product compared to fermented rooibos iced tea.

Thesis submitted in fulfillment of the requirements for the degree Master of Technology: Biomedical Technology In the Faculty of Health and Wellness Sciences At the Cape Peninsula University of Technology, 2012 / Human and experimental animal studies have shown that biomarkers of oxidative damage are elevated in subjects with certain diseases or risk factors. Consequently, it is hypothesized that oxidative stress plays an important role in the pathogenesis of these diseases and that dietary intake of, or supplementation with antioxidants may be protective or be useful therapeutic targets. This study was designed to investigate the modulatory effect of Camellia sinensis (Chinese green tea), Aspalathus linearis (rooibos herbal tea) and the two commercial supplements on the antioxidant status of the liver and kidney of tert-butyl hydroperoxide (t-BHP)-induced oxidative stress male Wistar rats. Rooibos and green tea are beverages well-known for their antioxidant content. Based on the specific beverage consumed, sixty male Wistar rats were randomly assigned into six groups, i.e. fermented rooibos (FRT), unfermented rooibos (URT), Chinese green tea (CGT), rooibos supplement (RTS), Chinese green tea supplement (GTS) and control (CTL). The animals had free access to the respective beverages and standard diet for 10 weeks, while oxidative stress was induced during the last 2 weeks via intraperitoneal injection of 30 μM of t-BHP per 100 g body weight. Among all the beverage and/or supplement preparations, the commercial rooibos supplement had the highest total polyphenol content and antioxidant activity while fermented rooibos, as previously shown, had a lower antioxidant content and potency when compared to its unfermented counterpart. The ability of these beverages and/or supplements to modulate the antioxidant status in tissues was organ specific and varied according to the assessment method. When considering the liver, the intake of unfermented rooibos, Chinese green tea and the commercial rooibos supplement significantly (P<0.05) restored the t-BHP-induced reduction and increased the antioxidant status with regards to oxygen radical absorbance capacity and trolox equivalent antioxidant capacity (TEAC) levels. All the beverages and/or supplements also significantly (P<0.05) enhanced the renal antioxidant capacity as assessed by the TEAC assay. In what may be an indication of decreased oxidative stress, all the beverages were associated with a general decline in activities of the antioxidant enzymes which reached significant levels in renal superoxidase dismutase activity. Generally, the beverages did not impact significantly on lipid peroxidation (LPO) although there were differing trends in the two LPO markers assessed. While thiobarbituric acid reactive substances levels showed a declining trend in both tissues, the conjugated dienes were generally elevated. In conclusion, this study confirms Camellia sinensis and Aspalathus linearis as well as their two supplements as good sources of dietary antioxidants and results demonstrated that rooibos and green tea improved the liver and kidney antioxidant capacity of oxidative stress-induced rats. Their impact on antioxidant status in rats was shown to vary between organs and according to the method of assessment. Hence multi-method, multi-organ assessment may be a more informative approach in in vivo antioxidant studies.

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Biomedical Technology In the Faculty of Health and Wellness Sciences At the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2012 / Oxidative stress and chronic (low-grade) inflammation are inseparably interconnected and both have been implicated in the aetiology of many disease states. The use of plant extracts for disease prevention and therapeutic purposes, is gaining more attention because of the health benefits of the bioactive phytochemicals in these extracts. This thesis reports on the antioxidant status, the oxidative stress modulation and anti-inflammatory properties of fermented rooibos (Aspalathus linearis) and red palm oil (RPO) from the oil palm plant (Elaeis guineensis) using a long-term and two short-term in vivo models. In the first (long-term) study, the effect of chronic feeding of rooibos, RPO or their combination on the endogenous antioxidant system was investigated. Data from this study provided:  The first scientific evidence that chronic feeding of rooibos, RPO or their combination for 22 weeks did not adversely affect the liver or kidney function parameters.  The first scientific evidence that chronic feeding of rooibos alone, or together with RPO for 22 weeks modulated the endogenous antioxidant system by inhibiting MDA formation and augmenting the reduced glutathione status.  The first scientific evidence of an additive or synergistic interaction in the ability of rooibos and RPO to modulate the endogenous antioxidant system. The second (short-term) study investigated the protective effects of rooibos, RPO or their combination on tert-butyl hydroperoxide (t-BHP)-induced oxidative hepatotoxicity, and results from this study provided:  The first evidence of the ability of the two extracts, either alone or in combination to protect against t-BHP induced hepatotoxicity. Supplementation of rooibos, RPO or their combination for eight weeks reversed the hepatic damage induced by t-BHP. The changes induced by t-BHP in the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) were reversed by these plant extracts. The extracts, supplemented alone or combined prevented lipid peroxidation as shown by the decreased levels of conjugated dienes iv (CD) and malondialdehyde (MDA) and reversed the t-BHP.-induced impairment of the glutathione redox status. The third (short-term) study provided the first scientific evidence of the in vivo anti-inflammatory properties of rooibos and RPO. The properties were demonstrated using a lipopolysaccharide (LPS)-induced hepatic endotoxemic model by:  Providing the first evidence of an additive or synergistic interaction in the ability of the combined rooibos extract and RPO supplementation to reverse LPS-induced hepatic damage.  Providing the first evidence for the modulation of the inflammatory responses by rooibos extract, RPO or their combination. Supplementation of rooibos extract, RPO or their combination for four weeks, modulated LPS-induced inflammatory responses by inhibiting the synthesis of pro-inflammatory cytokines, tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6).  Providing evidence that the observed anti-inflammatory effects of rooibos and RPO may be related to their ability to modulate oxidative stress. Supplementation of rooibos extract, RPO or their combination for four weeks, prevented hepatic lipid peroxidation induced by LPS by decreasing CD and MDA formation in the liver. Changes induced in the activities of antioxidant enzymes were reversed and the glutathione redox status was augmented. Based on these study results, it is proposed that the ability of rooibos and RPO to protect the liver, modulate endogenous antioxidant system and inhibit inflammatory responses may be associated with the unique combination of antioxidant phytochemicals in both plant extracts. The study suggested possible mechanism(s) for the observed health effects, and the development of rooibos and RPO as nutraceuticals, which may be beneficial in the prophylactic management of oxidant-induced liver injury.

Thesis submitted in fulfilment of the requirements for the Doctor of Technology: Biomedical Technology In the Faculty of Health and Wellness At the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2012 / Diabetes mellitus is a major health problem not only in urban, but also in the rural areas and is diagnosed by the presence of high glucose levels in the blood. Oxidative stress is known to be actively involved in the onset and progression of diabetes and its complications. Antioxidants have important roles in biological systems by scavenging free radicals which may result in oxidative damage of biological molecules such as lipids, proteins and DNA. Red palm oil, originally from the tropical area of Africa, generally consumed as cooking oil, is known to have some beneficial health effects due to the presence of lipid soluble antioxidants such as carotenoids, tocopherols and tocotrienols. It also contains almost an equal proportion of both saturated and unsaturated fatty acids which makes it distinctive from other vegetable oils. Rooibos, on the other hand, is grown in the Cederberg area of the Western Cape in South Africa and it is commonly consumed as a beverage. It contains a complex profile of water soluble antioxidants (flavonoids) and its health promoting potentials have been reported extensively. Some of the flavonoids present in rooibos include aspalathin, nothofagin, quercetin, rutin and orientin. The objective of this research project was to examine the potential beneficial effects of the dietary intake of red palm oil and rooibos on streptozotocin-induced hyperglycaemia and its influence on the antioxidant status and some biochemical parameters in male Wistar rats. The preliminary phase of this study was designed to investigate the biochemical effects of these two plant products at different dosages following consumption for a period of 7 weeks. The preliminary study did not reveal any adverse effects of the different dosages of red palm oil (1 ml, 2 ml and 4 ml) and rooibos (2%, 4% and 6%) on the experimental rats following dietary intake for 7 weeks. However, these natural products showed an improvement in the antioxidant status of the rats at the different doses. Using a single dose each of both plant products from the preliminary study, the main study was performed to investigate the influence of these two plant products singly and in combination on the blood and liver of streptozotocin-induced hyperglycaemic male Wistar rats. In the main study, streptozotocin (50 mg/kg) dissolved in 0.1 M citrate buffer (pH 4.5) through intramuscular injection was used for the induction of diabetes which was confirmed by the presence of high blood glucose after 72 hours. Red palm oil or rooibos extract alone did not have any effect on the control of blood glucose in the diabetic rats. The dietary intake of the combined treatment with red palm and rooibos had more health promoting effects on the diabetic rats which included a decrease in blood glucose, glycosylated haemoglobin, fructosamine and increased insulin levels. There was a marked increase in liver glycogen levels in all the diabetic groups. Treatment with rooibos alone showed a decrease in glycogen levels in the diabetic rats. The presence of liver enzymes in the serum, commonly used as indicators of liver damage was increased in all the diabetic rats. However, the combined treatment of diabetic rats with red palm oil and rooibos protected the liver from injury. Red palm oil improved high density lipoprotein cholesterol levels (HDL-cholesterol) in the diabetic rats. There was no effect on the activity of glucokinase, the first enzyme in the the glycolytic pathway in both the untreated and treated diabetic rats. However, the activity of pyruvate kinase, the last enzyme in the glycolytic pathway was reduced in all the diabetic groups. The combined treatment with both red palm and rooibos increased the activity of pyruvate kinase. Oxidative stress was confirmed in the diabetic rats with an increase in the plasma thiobarbituric acid reactive substances (TBARS), an indicator of lipid peroxidation. Treatment of diabetic rats with rooibos and the combination of red palm oil and rooibos brought plasma TBARS to a level that was not significantly different from the normal control group. There was a non-significant reduction of total glutathione in the non-treated and treated diabetic groups. A non-significant increase in the activity of liver catalase was observed in all the treated diabetic groups. The activity of superoxide dismutase was significantly decreased in the liver of diabetic rats. Diabetic rats treated with red palm oil, rooibos and the combined treatment showed an increased activity of superoxide dismutase in the liver. Red palm oil and the combined treatment increased the activity of glutathione peroxidase in both the red blood cells and liver of diabetic rats. Red palm oil, rooibos and their combined treatments also improved the plasma antioxidant capacity such as ferric reducing antioxidant power (FRAP) and oxygen reducing absorbance capacity (ORAC) in the diabetic rats. In conclusion, oxidative stress is actively involved in the progression of diabetes mellitus. Red palm oil and rooibos, most especially their combined treatment showed significant beneficial health promoting effects in the diabetic rats. The remarkable effects of the combined treatment of red palm oil and rooibos in the diabetic rats could be due to their antioxidant profiles. Based on the findings from this study, it can be adduced that these plant products could help in the management of diabetes and its complications and therefore, suggested the need for further research studies on antioxidant therapy in the management of diabetes mellitus.