SUNScholar - Browsing by Author "Joubert, E."

Browsing by Author "Joubert, E."

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Aspalathin, a C-glucosyldihydrochalcone from rooibos improves the hypoglycemic potential of metformin in type 2 diabetic (db/db) mice
(Institute of Physiology, The Czech Academy of Sciences, 2018-07-25) Dludla, P. V.; Gabuza, K. B.; Muller, C. J. F.; Joubert, E.; Louw, J.; Johnson, R.
ENGLISH ABSTRACT: Metformin is the first line therapy of type 2 diabetics, but continued reduction of their life expectancy warrants further investigation into alternative treatment strategies. This study reports on the combinational use of metformin with aspalathin, a C-glucosyl dihydrochalcone with known glucose lowering and antioxidant properties, as an effective hypoglycemic therapy in a type 2 diabetic (db/db) mouse model. When tested as a monotherapy, a low dose of aspalathin (13 mg/kg) showed no effect, while a high dose (130 mg/kg) has already displayed a better potential than metformin in protecting against diabetes associated symptoms in db/db mice. Thus, it remains of interest to determine whether this dihydrochalcone can improve the efficacy of metformin. The results showed that this combination therapy was more effective than the use of metformin as a monotherapy in ameliorating diabetes associated symptoms, including abnormal raised fasting plasma glucose levels, impaired glucose tolerance, as well as excessively increased body weights and fat content. The treated mice also had reduced food and water consumption when compared to untreated controls, with a pronounced effect evident in the last week of treatment. Therefore, this study supports further investigations into the ameliorative effect of combination therapy of metformin and aspalathin against diabetes associated symptoms.
Changes in the phenolic composition and antioxidant activity of pinotage, cabernet sauvignon, chardonnay and chenin blanc wines during bottle ageing
(South African Society for Enology and Viticulture, 2005) De Beer, D.; Joubert, E.; Gelderblom, W. C. A.; Manley, M.
The effect of bottle ageing on the antioxidant activity of Pinotage, Cabernet Sauvignon, Chardonnay and Chenin blanc wines, using the 2,2'-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS•+) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH0) scavenging assays, was determined. Storage at 0°C, 15°C or 30°C for a period of 12 months resulted in a significant (p ≤ 0.05) decrease in both the total antioxidant activity (TAAAnTs and TAAoPPH) and the total phenol content of the wines. The antioxidant potency of the total phenols of most of the wines, which is a ratio of antioxidant activity to the total phenol content, also decreased. The total anthocyanins in the red wines decreased significantly (p ≤ 0.05) over 12 months except for storage at 0°C, while the flavanol content of the Pinotage, Cabernet Sauvignon and Chardonnay wines increased up to nine months storage with a subsequent decrease to 12 months. The flavonol content of all the wines decreased, while only minor changes in their hydroxycinnamate content were observed during the storage period. Understanding the complexity of these reactions may provide clues for stabilising especially red wines to preserve the antioxidant activity without losing the beneficial effects of colouring and flavour development during bottle ageing.
Characterisation of pinotage wine during maturation on different oak products
(SASEV, 2008-01) De Beer, D.; Joubert, E.; Marais, J.; Du Toit, W.; Fourie, B.; Manley, M.
The effect of oak contact on the phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines was investigated during maturation. Oak maturation included traditional treatments, such as new, second-fill and third-fill barrels, as well as alternative treatments (oak chips, staves, extract and dust) applied in old barrels over a period of 28 weeks. Oak maturation using traditional and alternative treatments improved the objective colour of Pinotage wine by decreasing the L* value. Losses in TAC caused by decreased concentrations of monomeric phenolic compounds (most anthocyanins, flavan-3-ols, flavonols and hydroxycinnamic acids) during oak maturation were negated by increased concentrations of gallic acid and the formation of new oligomeric and polymeric pigments. Wine maturation in stainless steel containers also resulted in a decrease in anthocyanin content. The decrease in phenolic acid content for wines matured in stainless steel was less pronounced, while their flavan-3-ol content remained stable. The new-barrel treatment had the most pronounced effect on all parameters. Oak maturation can be used for the production of Pinotage wine when the retention of TAC is a high priority.
Chemical characterization of the constituents of the aroma of honeybush, Cyclopia genistoides
(Elsevier, 2008-01) Le Roux, M.; Cronje, J. C.; Joubert, E.; Burger, B. V.
A high-capacity headspace sample enrichment probe (SEP) was used in conjunction with gas chromatography-mass spectrometry (GC-MS) to analyse the volatile organic compounds present in the aroma of dry or infused, unfermented (green) and fermented C. genistoides, one of the South African Cyclopia species from which a herbal tea, known as honeybush tea, is made. Seventy-seven compounds were identified in the volatile fraction of the aroma of dry, green C. genistoides, comprising, inter alia, a large number of saturated and unsaturated alcohols, aldehydes and methyl ketones. In the aroma of dry, as well as infused, fermented C. genistoides, 79 compounds were identified, 46 of which were terpenoids that were mostly present in much lower relative concentrations in the unfermented material. The methodology developed and the results obtained in the analysis of the aroma of C. genistoides provide a basis for ongoing comparative studies on the chemical composition of a series of prominent Cyclopia species with the view to developing a rapid screening device and protocol for honeybush tea evaluation. © 2007 SAAB.
Climatic region and vine structure : effect on pinotage wine phenolic composition, total antioxidant capacity and colour
(South African Society for Enology and Viticulture, 2006) De Beer, D.; Joubert, E.; Marais, J.; Van Schalkwyk, D.; Manley, M.
The phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines of the 2001, 2002 and 2003 vintages were investigated, using spectrophotometric, high-performance liquid chromatography (HPLC), free radical scavenging and objective colour analyses. Grapes were harvested from grapevines in three climatic regions ranging from cool to warm, with bush (20- and 30-cm trunk height) and trellised (30- and 60-cm trunk heights) vine treatments, on several vineyard sites in each climatic area. Climatic region had a significant effect on the content of several phenolic compounds; the concentration of anthocyanin monoglucosides, flavonols, flavan-3-ols and tartaric acid esters of hydroxycinnamic acids generally increased as the climatic region becomes cooler, while concentrations of acylated derivatives and free hydroxycinnamic acids decreased. Wines made from bush vines contained higher concentrations of flavonols, gallic acid and flavan-3-ols than those from trellised vines, but lower concentrations of some anthocyanin monoglucosides and acylated derivatives, as well as non-coloured polymers. These trends resulted in differences in TAC and objective colour parameters, although the different vintages did not show the same trends in all cases. More vintages should therefore be investigated to clarify these effects. Wines from the cool climatic regions and from bush vines were generally darker coloured, with higher TAC than those from the warm climatic regions and bush vines, respectively. High TAC, therefore, coincided with higher colour quality. Variations in TAC were partly explained by trends for individual phenolic compounds, although unknown compounds played a major role.
Development of chemical-based reference standards for rooibos and honeybush aroma lexicons
(Elsevier, 2019) Du Preez, B. V. P.; De Beer, D.; Moelich, E. I.; Muller, M.; Joubert, E.
The honeybush sensory wheel was revised, using a large sample set (n = 585) comprising of the major commercial Cyclopia species, i.e. C. intermedia, C. subternata and C. genistoides. Only positive and negative aroma attributes were included in the wheel. Chemicals were identified to serve as reference standards for the honeybush (Cyclopia spp.) lexicon. Similarly, chemical-based reference standards were identified for the rooibos (Aspalathus linearis) lexicon. From a comprehensive literature search and gas chromatography–mass spectrometry analyses, chemicals were screened by an expert panel for their suitability in terms of typicality of the target aroma. Each chemical was evaluated in a ‘base tea’ and compared to a specific ‘reference tea’ exhibiting a high intensity of the target aroma. A total of 30 and 44 chemicals for rooibos and honeybush, respectively, were selected for validation by a trained panel. Descriptive sensory analysis was conducted to assign typicality and intensity scores for each chemical representing a target aroma attribute. Several chemicals were identified as suitable reference standards for the following aroma notes: isophorone (‘rooibos-woody’), maltyl isobutyrate (‘caramel’), cis-3-hexenol (‘green grass’), 4-oxoisophorone (‘seaweed’) and 2,4,6-trichloroanisole (‘musty/mouldy’) for rooibos; and 2-acetyl-5-methylfuran (‘woody’), levulinic acid (‘fynbos-sweet’), maltyl isobutyrate (‘caramel’), and 2-acetylpyrrole (‘nutty’) for honeybush.
Divide and conquer may not be the optimal approach to retain the desirable estrogenic attributes of the cyclopia nutraceutical extract, SM6Met
(Public Library of Science, 2015) Mortimer, M.; Visser, K.; De Beer, D.; Joubert, E.; Louw, A.
The genus Cyclopia, an indigenous South African fynbos plant used to prepare honeybush tea, contains phytoestrogenic compounds. An extract from C. subternata, SM6Met, displays three desirable estrogenic attributes for future development of a phytoestrogenic nutraceutical, namely, ERα antagonism, ERβ agonism, and also antagonism of E2-induced breast cancer cell proliferation. Activity-guided fractionation of SM6Met was used in an attempt to isolate and identify compounds conferring the desirable estrogenic profile to SM6Met. Initial liquid-liquid fractionation of SM6Met yielded a polar fraction (PF) and a non-polar fraction (NPF), with the desirable estrogenic attributes retained in the NPF. Subsequent high performance counter-current chromatography (HPCCC) fractionation of the NPF yielded three fractions (F1-F3). Interestingly, the fractions revealed separation of the previously demonstrated positive estrogenic attributes of the NPF into separate fractions, with F1 and F2 acting as ERα antagonists, only F2 inducing antagonism of E2-induced breast cancer cell proliferation and only F3 retaining robust ERβ agonist activity. In terms of major polyphenols, quantitative HPLC and liquid chromatography tandem mass spectrometry (LC-MS/MS) indicated that HPCCC fractionation resulted in a divergence of polyphenolic classes, with F1 emerging as the dihydrochalcone-rich fraction and F2 as the flavanone- and benzophenone-rich fraction, while the xanthones, flavones and phenolic acids were retained in F3. F3 was re-engineered into F3R by reassembling the major polyphenols identified in the fraction. F3R could, however, not replicate the effect of F3. In conclusion, although activity-guided fractionation results suggest that retention of all the desirable estrogenic attributes of the original SM6Met in one fraction is not an attainable goal, fractionation is a useful tool to enhance specific desirable estrogenic attributes.
Effect of oxygenation during maturation on phenolic composition, total antioxidant capacity, colour and sensory quality of pinotage wine
(SASEV, 2008-10) De Beer, D.; Joubert, E.; Marais, J.; Manley, M.
The effect of oxygenation on the phenolic composition, total antioxidant capacity (TAC), colour and sensory quality was investigated during the maturation of Pinotage wines. Oxygenation was carried out in discrete monthly doses at two oxygen dosages (2.5 and 5.0 mg O2/L/month) for zero, two, four and six months. Oxygenation at the lower dosage for two months had beneficial effects on the colour and sensory quality of Pinotage wine. The higher oxygen dosage (all times) and longer times (all dosages) had a substantial detrimental effect on the overall sensory quality of the wine. A decrease in the TAC of the wine was observed for all the treatment combinations, despite increased concentrations of gallic acid. During the following harvest, a modified oxygenation treatment, entailing 1.0 mg O2/L in discrete doses every two weeks for two months, was tested. It had little effect on the wine phenolic composition and was not detrimental to the TAC of the wine. The modified oxygenation protocol significantly reduced the berry/ plum intensity of the Pinotage wine without negatively affecting the overall sensory quality. Oxygen addition on a continuous basis may also be less detrimental to the TAC of the wine and provide improved sensory quality.
Effect of rooibos and honeybush tea extracts against Botrytis cinerea
(SASEV, 2008-02) Coetzee, G.; Marx, I. J.; Pengilly, M.; Bushula, V. S.; Joubert, E.; Bloom, M.
Green tea extracts from the indigenous South African rooibos (Aspalathus linearis) and honeybush (Cyclopia species) plants were evaluated as potential antifungal agents against the plant pathogen Botrytis cinerea. When applied at 10 mg/ml, the tea extracts stimulated biomass production in B. cinerea by more than 3-fold after 24 hrs. This induction could not be linked directly to the presence of selected micro- and macronutrients or antioxidants in the extracts, suggesting a complex set of yet unidentified factors that may act synergistically to enhance cell growth. However, when applied at 100 mg/ml, the A. linearis and C. genistoides extracts reduced spore germination of B. cinerea by 33.3% and 16.7%, respectively. This suggests that the tea extracts contain active compounds that should be further investigated for their potential as natural anti-fungal agents.
Engagement of dietetic students and students with hearing loss : experiences and perceptions of both groups
(Health and Medical Publishing Group, 2018) Smit, Y.; Marais, M.; Philips, L.; Donald, H.; Joubert, E.
Background. Final-year dietetic students from Stellenbosch University (SU) present selected training sessions during their Rural Clinical School (RCS) rotation to professional cookery students of the National Institute for the Deaf (NID). Objective. To describe experiences and perceptions of dietetic students and NID students before and after training sessions. Methods. A descriptive, phenomenological approach was followed. SU students (N=23) reflected on experiences before and after providing training to NID students. Two focus group discussions were conducted with NID students (N=19) after training to explore their experiences related to the training. An experienced interpreter facilitated discussion topics using South African Sign Language (SASL). Voice recordings were transcribed verbatim and thematic content analysis was performed manually. Results. NID students described feelings of uncertainty and fear of the unknown prior to the training. These feelings turned to excitement and curiosity as the presentations continued. They were positive about the learning experience and described it as wonderful and interesting. SU students described it as challenging, but valuable in gaining insight into living with deafness. The experience positively influenced their professional and personal development. Students were appreciative of and grateful for the opportunity to engage with and learn from each other. Suggestions were made to improve future training sessions based on identified barriers, such as overcoming communication challenges and clarifying reciprocal misperceptions. Perceptions changed when similarities between student groups were realised. Conclusion. The overwhelmingly positive experience of both groups is a strong motivation to continue with this initiative. SU students recognised the importance of health promotion to persons with impairments.
Maceration before and during fermentation : effect on pinotage wine phenolic composition, total antioxidant capacity and objective colour parameters
(South African Society for Enology and Viticulture, 2006) De Beer, D.; Joubert, E.; Marais, J.; Manley, M.
Low-temperature maceration treatments (1, 2 and 4 days at 10 and 15°C) before fermentation and juice/skin mixing treatments (punching-down, pumping-over and rotor action every hour and every 3 hours) during fermentation were investigated in terms of their effects on Pinotage wine phenolic composition, total antioxidant capacity (TAC) and colour over three vintages (2000 to 2002). Results for pre-fermentation maceration were not consistent between vintages. Very few significant differences in the phenolic content, TAC and objective colour parameters were observed between the control wines and wines subjected to different pre-fermentation maceration treatments. Pre-fermentation maceration, especially at 15°C, resulted in wines with increased vitisin A content. Improvement of wine quality when using pre-fermentation maceration treatments at 10°C was noted previously, while no detrimental effect on the wine TAC was observed. The pumping-over treatment yielded wines with lower TAC and phenol content, as well as less favourable objective colour values, indicating that the punching-down or rotor treatment would be preferred. Although mixing at hourly intervals yielded a higher content of some phenolic compounds compared to the 3-hour interval mixing, mixing frequency did not affect the TAC of the wine. The objective colour parameters, h* and b*, were slightly lower at the higher mixing frequency in 2002 indicating a shift in the direction of a magenta hue.
Modulation of Hepatic Drug Metabolizing Enzymes and Oxidative Status by Rooibos (Aspalathus linearis) and Honeybush (Cyclopia intermedia), Green and Black (Camellia sinensis) Teas in Rats
(2003) Marnewick, J. L.; Joubert, E.; Swart, P.; Der Westhuizen, F. V.; Gelderblom, W. C.
Rooibos and honeybush teas significantly (P < 0.05) enhanced the activity of cytosolic glutathione S-transferase alpha. A significant (P < 0.05) to marginal (P < 0.1) increase in the activity of the microsomal UDP-glucuronosyl transferase was obtained with unprocessed rooibos and honeybush teas, respectively. Oxidized glutathione (GSSG) levels were significantly (P < 0.05) reduced in the liver of all tea treated rats while reduced glutathione (GSH) was markedly increased in the liver of the herbal tea treated rats. These changes resulted in a significant (P < 0.05) increase in the GSH/GSSG ratio by the unprocessed, processed rooibos and unprocessed honeybush teas. Green and black teas markedly to significantly decreased the oxygen radical absorbance capacity in liver homogenates, respectively. Modulation of phase II drug metabolizing enzymes and oxidative status in the liver may be important events in the protection against adverse effects related to mutagenesis and oxidative damage.
Phenolic compounds : a review of their possible role as in vivo antioxidants of wine
(South African Society for Enology and Viticulture, 2002) De Beer, D.; Joubert, E.; Gelderblom, W. C. A.; Manley, M.
Phenolic compounds are a large and complex group of chemical constituents found in red and white wines which not only affect their quality, but also contribute to their beneficial health effects. The antioxidant properties of phenolic compounds are important in determining their role as protective agents against free radical-mediated disease processes. This review discusses the principles of oxidative stress and the resultant cellular damage caused by lipid peroxidation in vivo. Different groups of wine phenolic compounds are detailed, with specific reference to their in vitro antioxidant activity and their relative potency as free radical scavengers. The absorption and bioavailability of phenolic compounds from dietary sources is discussed.
Screening of four Cyclopia (honeybush) species for putative phyto-oestrogenic activity by oestrogen receptor binding assays
(AOSIS OpenJournals, 2007) Verhoog, N. J. D.; Joubert, E.; Louw, Ann
Phyto-oestrogens mediate an oestrogenic effect through binding to the oestrogen receptor (ER) subtypes, ERα and ERβ. Four commercially available Cyclopia (honeybush) species - C. intermedia, C. subternata, C. genistoides and C. sessiliflora - together with nine commercially obtainable polyphenols present in some or all of the species, were screened for phyto-oestrogenic activity, using a competitive whole-cell ER binding assay. Only naringenin, formononetin and luteolin were able significantly to displace 3H-E2 from hERα, whereas luteolin, naringenin, formononetin, eriodictyol, narirutin and eriocitrin displaced 3H-E2 from hERβ. Mangiferin, hesperidin and hesperetin did not bind to either receptor subtype. To our knowledge, this is the first time that binding of eriodictyol, eriocitrin and narirutin to the hERβ has been shown. Furthermore, both aqueous and methanol extracts from three independent harvestings of each Cyclopia species were screened. The results suggest that C. genistoides and C. subternata display significant phyto-oestrogenic activity and that methanol extracts from 'unfermented' (unoxidized) plant material generally display greater activity. Great variation exists within a species, however, with one C. genistoides harvesting displacing 3H-E2 from both ER subtypes, while another harvesting displaced 3H-E2 from only hERβ, and a third did not displace 3H-E2 from either receptor subtype.
South African herbal teas : Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides - a review
(Elsevier, 2008-10) Joubert, E.; Gelderblom, W. C. A.; Louw, Ann; De Beer, D.
Rooibos (Aspalathus linearis (Brum.f) Dahlg.) and honeybush (Cyclopia Vent. species) are popular indigenous South African herbal teas enjoyed for their taste and aroma. Traditional medicinal uses of rooibos in South Africa include alleviation of infantile colic, allergies, asthma and dermatological problems, while a decoction of honeybushwas used as a restorative and as an expectorant in chronic catarrh and pulmonary tuberculosis. Traditional medicinal uses of Athrixia phylicoides DC., or bush tea, another indigenous South African plant with very limited localised use as herbal tea, include treatment of boils, acne, infected wounds and infected throats. Currently rooibos and honeybush are produced for the herbal tea market, while bush tea has potential for commercialisation. A summary of the historical and modern uses, botany, distribution, industry and chemical composition of these herbal teas is presented. A comprehensive discussion of in vitro, ex vivo and in vivo biological properties, required to expand their applications as nutraceutical and cosmeceutical products, is included, with the mainemphasis on rooibos. Future research needs include more comprehensive chemical characterisation of extracts, identification of marker compounds for extract standardisation and quality control, bioavailability and identification of bio-markers of dietary exposure, investigation of possible herb–drug interactions and plant improvement with regards to composition and bioactivity.
Synovial haemangioma as a cause for a traumatic haemarthrosis of the knee - a case report
(Champagne Media, 2013) Joubert, E.
ENGLISH ABSTRACT: An adult patient presented with repeated episodes of haemarthrosis of the knee. No trauma history could be elicited. An arthroscopy of his knee was performed and a lesion identified. Histologic examination showed it to be a synovial haemangioma (capillary type).

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