Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. / Antimutagenic activity of aqueous extracts of fermented and unfermented Cyclopia spp., i.e. C. intermedia, C. subternata, C. genistoides and C. sessiliflora against metabolically activated aflatoxin B1 (AFB1) in the Salmonella mutagenicity assay with tester strain TA100, was compared to that of fermented and unfermented Aspalathus linearis (rooibos) and Camellia sinensis (black, oolong and green) teas. Possible mechanisms involved in in vitro antimutagenic activity of these teas were investigated, i.e. the stabilising effect of the unfermented Cyclopia spp., unfermented rooibos and green tea on rat liver cytochrome P450 in the S9 fraction from Aroclor 1254 treated rats and their modulation of aniline-induced Type II difference spectra in the microsomal fraction. Inhibition of lipid peroxidation in rat liver S9, by the teas, was assessed to determine whether protection against lipid peroxidation may play a role in cytochrome P450 stability in vitro. Correlation of the antimutagenic activity of the teas with their stabilising effect on cytochrome P450 and inhibition of lipid peroxidation, provided insight into possibly related mechanisms. Antimutagenic activity correlated weakly with a decreased stabilising effect of the teas on cytochrome P450 (r = 0.411, P = 0.013) and the inhibition of lipid peroxidation (r = 0.475, P = 0.003). Decreased stability of cytochrome P450 was associated with substantial lipid peroxidation occurring in rat liver S9. Effective inhibition of lipid peroxidation and stabilising of cytochrome P450 in S9 was evident in the presence of the teas, but no correlation (r = 0.018, P = 0.915) existed for the effect of unfermented teas on cytochrome P450 stability with inhibition of lipid peroxidation. Black tea exhibited the highest protection against AFB1-induced mutagenesis and fermented C. intermedia offered the least protection. “Fermentation” resulted in increased antimutagenic activity of Camellia sinensis and rooibos teas, while the antimutagenic activity of Cyclopia spp. decreased with fermentation except for C. genistoides. Unfermented teas significantly (P < 0.05) stabilised cytochrome P450, with rooibos more effective (P < 0.05) than green tea, but similar (P < 0.05) to Cyclopia spp. Green tea demonstrated the highest inhibition of lipid peroxidation, while the inhibition exerted by rooibos was similar (P > 0.05) to unfermented Cyclopia spp., except for C. genistoides exhibiting the least inhibition. Total polyphenol, flavanol and flavonol/flavone contents of the respective teas were correlated with activity in terms of antimutagenicity, stabilising of cytochrome P450 and inhibition of lipid peroxidation. Antimutagenic activity of Cyclopia spp. correlated with its total polyphenol (r = 0.805, P < 0.0001) and flavanol (r = 0.653, P < 0.0001) contents, while a weak negative correlation (r = -0.456, P = 0.026) was observed for the inhibition of lipid peroxidation by unfermented Cyclopia spp. with the flavonol/flavone content. Antimutagenicity of Cyclopia spp. correlated weakly (r = 0.363, P = 0.012) with its hesperidin content. Antimutagenic activity of rooibos tea correlated moderately (r = 0.751, P < 0.005) with its flavonol/flavone content and specifically the flavones orientin (r = 0.674, P < 0.023) and iso-orientin (r = 0.728, P < 0.011). A strong negative correlation (r = -0.918, P < 0.0001) of antimutagenicity of rooibos with its aspalathin content was observed. Antimutagenic activity of Camellia sinensis teas did not correlate with their total polyphenol, flavanol or flavonol/flavone contents. The flavanol content of green tea showed a good, but marginal (P < 0.1) correlation (r = 0.824, P = 0.086) with decreased cytochrome P450 stability. The modulation of aniline-induced Type II binding to microsomal cytochrome P450 by green tea differed significantly (P < 0.05) from the modulation exhibited by rooibos and Cyclopia spp. Flavonoid glycosylation appeared to influence antimutagenic activity, stabilising of cytochrome P450 and modulation of substrate binding of selected phenolic compounds. The present study indicates that rooibos and Cyclopia spp. have in vitro antimutagenic activity against AFB1, suggesting that consumption of these two herbal teas may have beneficial health effects. It is also suggested that stabilising of cytochrome P450 by tea, and interaction of tea constituents with cytochrome P450, may influence their in vitro antimutagenic activity.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Honeybush (Cyclopia spp.) is indigenous to South Africa and consists of more than 20 species of which only a few are used to make a herbal tea with a unique aroma and sweet taste. The aroma of unfermented and fermented honeybush tea differs considerably, indicating that changes take place in the chemical composition of the aroma during the fermentation process. Using a sample enrichment probe (SEP) and gas chromatography-mass spectrometry (GC-MS), the chemical composition of the aroma of unfermented and fermented C. genistoides, was analyzed and the resulting aroma profiles were compared. A total of 74 compounds were identified in the unfermented honeybush aroma, comprising, inter alia, a large number of saturated and unsaturated alcohols, aldehydes and methyl ketones that were found to be either absent, or present in lower relative concentrations, in the aroma of fermented honeybush. Most of these compounds, including 6-methyl-5-hepten-2-one, identified as one of the major constituents of unfermented honeybush, are probably responsible for its grassy, hay-like aroma. In the aroma of fermented honeybush 70 compounds were identified, of which 36 were found to be terpenoids. These compounds are probably responsible for the pleasant sweet aroma of the fermented honeybush. For instance, the major aroma constituent in the fermented honeybush, α-terpineol, is known to have a delicately floral and sweet odour. Other terpenoids occuring in significant quantities in the fermented honeybush, are linalool, cis and trans linalool oxide, nerol, geraniol, 2,6-dimethyl-1,7-octadien-3,6-diol, hexahydrofarnecyl acetone and phytol. These terpenoids are known to have sweet, sweet-woody en floral odours that probably contribute to the overall sweet aroma of the fermented honeybush. In the aroma of the unfermented honeybush a total of 25 terpenoids was identified, of which geranyl acetone, β-ionone, and dihydroactinidiolide are the most significant, since they are present in higher relative concentrations compared to the same terpenoids in the fermented honeybush. These three terpenoids have overall woody and even slightly green odours which contribute to the typical aroma of the unfermented honeybush. The terpenoids present in the aroma of unfermented and fermented honeybush belong to the following compound classes: • Terpenes • Terpene alcohols • Terpene aldehydes • Ketoterpenes • Terpene ethers • Terpene lactones Apart from the terpenoids present in the aroma of unfermented and fermented honeybush, the following classes of compounds are also present: • Aliphatic hydrocarbons (saturated) • Aliphatic alcohols (saturated and unsaturated) • Phenols • Aliphatic aldehydes (saturated and unsaturated) • Aliphatic ketones (saturated and unsaturated) • Aliphatic carboxylic acids (saturated) • Esters (methyl esters, ethyl and higher esters and aromatic esters) • Furane compounds • Lactones The present research was done to compare the chemical composition of the aroma of unfermented and fermented honeybush of one particular species, namely C. genistoides, to obtain an understanding of the evolution and/or disappearance of volatile compounds during fermentation that ultimately could help to identify compounds or compound types and their precursors responsible for its unique sweet aroma.