SUNScholar - Browsing by Author "De Beer, Dalene"

Browsing by Author "De Beer, Dalene"

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The antioxidant activity of South African wines in different test systems as affected by cultivar and ageing
(Stellenbosch : University of Stellenbosch, 2002-03) De Beer, Dalene; Joubert, E.; Gelderblom, W. C. A.; Manley, M.; University of Stellenbosch. Faculty of Agriscience. Dept. of Food Science.
ENGLISH ABSTRACT: Phenolic compounds in wine, due to their antioxidant activity, are reportedly responsible for the health-promoting properties of wines. The effect of cultivar and in-bottle ageing on the antioxidant activity of South African wines in different types of antioxidant assays was, therefore, investigated. The antioxidant activity of commercial South African red (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) cultivar wines was compared using the 2,2’-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS·+) scavenging, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) scavenging and microsomal lipid peroxidation (MLP) assays. The red wines was more effective than the white wines on an “as-is” and an equal total phenol content. The total antioxidant activity (TAAABTS and TAADPPH) of Ruby Cabernet was the lowest of the red wines, but the antioxidant potency (APABTS and APDPPH) of red wine phenolic fractions did not differ (P ³ 0.05). Ruby Cabernet and Pinotage were the least effective inhibitors of MLP, while Merlot was the most effective of the red wines. Pinotage phenolic fractions had lower (P < 0.05) APMLP than that of other red wines. Of the white wines, Chardonnay and Chenin blanc had the highest and lowest effectivity respectively according to all antioxidant parameters. Ascorbic acid present in some wines increased and decreased their TAA and % MLP inhibition respectively. TAA and % MLP inhibition correlated well (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavanol content of red wines and tartaric acid ester content of white wines. The % MLP inhibition also correlated well with flavanol content of white wines. No correlation (P > 0.01) was obtained between TAA or % MLP inhibition and monomeric anthocyanin content of red wines. In the deoxyribose assay, red wines were more pro-oxidant and exhibited lower hydroxyl radical scavenging and metal chelating abilities than white wines. The effect of in-bottle ageing on antioxidant activity of wines was determined using the ABTS·+ and DPPH· scavenging assays. The TAA and total phenol content of experimental red (Pinotage and Cabernet Sauvignon)and white (Chardonnay and Chenin blanc) cultivar wines, decreased (P < 0.05) during 12 months of storage at 0, 15 and 30 ºC. The TAAABTS of Cabernet Sauvignon and Chardonnay, stored at 30 ºC were lower (P < 0.05) than at 0 ºC. The APABTS and APDPPH of most wines also decreased during storage. The monomeric anthocyanin content of red wines decreased (P < 0.05) rapidly at 15 and 30 ºC. The flavanol content of wines (except Chenin blanc) increased during the first 9 months, decreasing again after 12 months, while minor changes in the flavonol and tartaric acid ester content of both red and white wines were observed. The TAAABTS exhibited a good correlation (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavonol and tartaric acid ester content of red and white wines and flavanol content of white wines. The monomeric anthocyanin content of red wines correlated (r = 0.50, P < 0.001) weakly with TAAABTS. The decrease in the TAAABTS of wines could thus be mainly attributed to a decrease in their total phenol content.
Antioxidant capacity of Pinotage wine as affected by viticultural and enological practices
(Stellenbosch: University of Stellenbosch, 2006-12) De Beer, Dalene; Joubert, E.; Marais, Jeannine; Manley, M.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science.
The aim of the study was to provide the South African wine industry with guidelines for the production of Pinotage wines with optimal total antioxidant capacity (TAC), while retaining sensory quality. The contribution of individual phenolic compounds to the wine TAC is important in this regard. The wine TAC was measured with the 2,2 -azino-di(3-ethylbenzo-thiazoline-sulphonic acid radical cation) (ABTS +) scavenging assay. The contributions of individual phenolic compounds to the wine TAC were calculated from their content in the wines and the Trolox equivalent antioxidant capacity (TEAC) of pure phenolic standards. The effects of climate region, vine structure, enological techniques (pre-fermentation maceration, juice/skin mixing, addition of commercial tannins, extended maceration) and maturation (oak barrels, alternative oak products, oxygenation) on the phenolic composition, TAC and sensory quality of Pinotage wines were also investigated. The TEAC values of quercetin-3-galactoside, isorhamnetin and peonidin-3-glucoside were reported for the first time. TEAC values observed for most compounds were much lower than those reported previously, although TEAC values for gallic acid, caftaric acid, caffeic acid and kaempferol were consistent with some previous reports. Caftaric acid and malvidin-3-glucoside were the largest contributors to the wine TAC. The contents of monomeric phenolic compounds and procyanidin B1, however, only explained a small amount (between 11 and 24%) of the wine TAC, with the remaining TAC attributed to oligomeric and polymeric phenolic compounds and other unknown compounds. Some synergy between different monomeric phenolic compounds was also demonstrated. All the viticultural and enological factors investigated affected the phenolic composition of Pinotage wines, while the wine TAC was only affected by some treatments. Changes in wine TAC could not always be explained by changes in phenolic composition as the contribution of oligomeric, polymeric and unknown compounds could not be assessed, but could play a large role. Differences in wine colour were also difficult to explain due to the large number of factors involved and the dark wine colour, which made objective measurements difficult. The concentration of vitisin A, an orange-red pyranoanthocyanin, was increased consistently as a result of prefermentation maceration treatments and affected the wine colour of oxygenated wines. Increased wine TAC was observed when cultivating Pinotage grapes on bush vines and in cooler climatic regions, compared to cultivation on trellised vines in warmer climatic regions. All the climatic regions and vine structure treatments, however, resulted in wines with good sensory quality. In terms of enological techniques, pumping-over, as opposed to punching-down and rotor treatments, is not recommended as a juice/skin mixing technique, due to reduced wine TAC, colour and sensory quality. Pre-fermentation maceration, addition of commercial tannin preparations, and oak maturation using traditional and alternative treatments, resulted in improved sensory quality, but with no change in wine TAC. However, optimisation of the tannin addition protocol may result in increased wine TAC if additions are made after fermentation or higher dosages are used. Oxygenation of Pinotage wine needs further investigation to optimise the protocol, as improvements to the wine colour and fullness were observed for some treatments, but loss of sensory quality and TAC were observed in most cases.
Chemoprevention of LA7-induced mammary tumor growth by SM6Met, a well-characterized cyclopia extract
(Frontiers, 2018) Oyenihi, Omolola R.; Krygsman, Annadie; Verhoog, Nicolette; De Beer, Dalene; Saayman, Michael J.; Mouton, Thys M.; Louw, Ann; Wong, Vincent Kam Wai
Breast cancer (BC) is the leading cause of cancer-related deaths in women. Chemoprevention of BC by using plant extracts is gaining attention. SM6Met, a wellcharacterized extract of Cyclopia subternata with reported selective estrogen receptor subtype activity, has shown tumor suppressive effects in a chemically induced BC model in rats, which is known to be estrogen responsive. However, there is no information on the estrogen sensitivity of the relatively new orthotopic model of LA7 cell-induced mammary tumors. In the present study, the potential chemopreventative and side-effect profile of SM6Met on LA7 cell-induced tumor growth was evaluated, as was the effects of 17b-estradiol and standard-of-care (SOC) endocrine therapies, such as tamoxifen (TAM), letrozole (LET), and fulvestrant (FUL). Tumor growth was observed in the tumorvehicle control group until day 10 post tumor induction, which declined afterward on days 12–14. SM6Met suppressed tumor growth to the same extent as TAM, while LET, but not FUL, also showed substantial anti-tumor effects. Short-term 17b-estradiol treatment reduced tumor volume on days prior to day 10, whereas tumor promoting effects were observed during long-term treatment, which was especially evident at later time points. Marked elevation in serum markers of liver injury, which was further supported by histological evaluation, was observed in the vehicle-treated tumor control, TAM, LET, and long-term 17b-estradiol treatment groups. Alterations in the lipid profiles were also observed in the 17b-estradiol treatment groups. In contrast, SM6Met did not augment the increase in serum levels of liver injury biomarkers caused by tumor induction and no effect was observed on lipid profiles. In summary, the results from the current study demonstrate the chemopreventative effect of SM6Met on mammary tumor growth, which was comparable to that of TAM, without eliciting the negative side-effects observed with this SOC endocrine therapy. Furthermore, the results of this study also showed some responsiveness of LA7-induced tumors to estrogen and SOC endocrine therapies. Thus, this model may be useful in evaluating potential endocrine therapies for hormone responsive BC. Keywords: chemoprevention, Cyclopia, mammary tumor, phytoestrogen, tamoxifen, letrozole, fulvestrant
Comprehensive phenolic profiling of Cyclopia genistoides (L.) Vent. by LC-DAD-MS and -MS/MS reveals novel xanthone and benzophenone constituents
(MDPI, 2014-08) Beelders, Theresa; De Beer, Dalene; Stander, Maria A.; Joubert, Elizabeth
A high-performance liquid chromatographic (HPLC) method coupled with diode-array detection (DAD) was optimized for the qualitative analysis of aqueous extracts of Cyclopia genistoides. Comprehensive insight into the phenolic profile of unfermented and fermented sample extracts was achieved with the identification of ten compounds based on comparison with authentic reference standards and the tentative identification of 30 additional compounds by means of electrospray ionization mass spectrometry (ESI-MS) and tandem MS detection. Three iriflophenone-di-O,C-hexoside isomers, three xanthone-dihydrochalcone derivatives and one dihydrochalcone are herein tentatively identified for the first time in C. genistoides. Of special interest is one iriflophenone-di-O,C-hexoside present in large amounts. New compounds (tentatively) identified for the first time in this species, and also in the genus Cyclopia, include two aromatic amino acids, one flavone, an iriflophenone-di-C-hexoside, a maclurin-di-O,C-hexoside, two tetrahydroxyxanthone-C-hexoside isomers, a tetrahydroxyxanthone-di-O,C-hexoside, two symmetric tetrahydroxyxanthone-C-hexoside dimers, nine glycosylated flavanone derivatives and five glycosylated phenolic acid derivatives. The presence of new compound subclasses in Cyclopia, namely aromatic amino acids and glycosylated phenolic acids, was demonstrated. The HPLC-DAD method was successfully validated and applied to the quantitative analysis of the paired sample extracts. In-depth analysis of the chemical composition of C. genistoides hot water extracts gave a better understanding of the chemistry of this species that will guide further research into its medicinal properties and potential uses.
Food ingredient extracts of Cyclopia subternata (Honeybush) : variation in phenolic composition and antioxidant capacity
(MDPI, 2012) De Beer, Dalene; Schulze, Alexandra E.; Joubert, Elizabeth; De Villiers, Andre; Malherbe, Christiaan J.; Stander, Maria A.
Cyclopia subternata plants are traditionally used for the production of the South African herbal tea, honeybush, and recently as aqueous extracts for the food industry. A C. subternata aqueous extract and mangiferin (a major constituent) are known to have anti-diabetic properties. Variation in phenolic composition and antioxidant capacity is expected due to cultivation largely from seedlings, having implications for extract standardization and quality control. Aqueous extracts from 64 seedlings of the same age, cultivated under the same environmental conditions, were analyzed for individual compound content, total polyphenol (TP) content and total antioxidant capacity (TAC) in a number of assays. An HPLC method was developed and validated to allow quantification of xanthones (mangiferin, isomangiferin), flavanones (hesperidin, eriocitrin), a flavone (scolymoside), a benzophenone (iriflophenone-3-C-β-glucoside) and dihydrochalcones (phloretin-3',5'-di-C-β-glucoside, 3-hydroxyphloretin-3',5'-di-C-hexoside). Additional compounds were tentatively identified using mass spectrometric detection, with the presence of the 3-hydroxyphloretin-glycoside, an iriflophenone-di-O,C-hexoside, an eriodictyol-di-C-hexoside and vicenin-2 being demonstrated for the first time. Variability of the individual phenolic compound contents was generally higher than that of the TP content and TAC values. Among the phenolic compounds, scolymoside, hesperidin and iriflophenone-3-C-β-glucoside contents were the most variable. A combination of the measured parameters could be useful in product standardization by providing a basis for specifying minimum levels.
Intestinal transport characteristics and metabolism of C-glucosyl dihydrochalcone, aspalathin
(MDPI, 2017) Bowles, Sandra; Joubert, Elizabeth; De Beer, Dalene; Louw, Johan; Brunschwig, Christel; Njoroge, Mathew; Lawrence, Nina; Wiesner, Lubbe; Chibale, Kelly; Muller, Christo
Insight into the mechanisms of intestinal transport and metabolism of aspalathin will provide important information for dose optimisation, in particular for studies using mouse models. Aspalathin transportation across the intestinal barrier (Caco-2 monolayer) tested at 1–150 µM had an apparent rate of permeability (Papp) typical of poorly absorbed compounds (1.73 × 10⁻⁶cm/s). Major glucose transporters, sodium glucose linked transporter 1 (SGLT1) and glucose transporter 2 (GLUT2), and efflux protein (P-glycoprotein, PgP) (1.84 × 10⁻⁶ cm/s; efflux ratio: 1.1) were excluded as primary transporters, since the Papp of aspalathin was not affected by the presence of specific inhibitors. The Papp of aspalathin was also not affected by constituents of aspalathin-enriched rooibos extracts, but was affected by high glucose concentration (20.5 mM), which decreased the Papp value to 2.9 × 10⁻⁷ cm/s. Aspalathin metabolites (sulphated, glucuronidated and methylated) were found in mouse urine, but not in blood, following an oral dose of 50 mg/kg body weight of the pure compound. Sulphates were the predominant metabolites. These findings suggest that aspalathin is absorbed and metabolised in mice to mostly sulphate conjugates detected in urine. Mechanistically, we showed that aspalathin is not actively transported by the glucose transporters, but presumably passes the monolayer paracellularly.
Model development for predicting in vitro bio-capacity of green rooibos extract based on composition for application as screening tool in quality control
(Royal Society of Chemistry, 2020-03-09) Viraragavan, Amsha; Hlengwa, Nokulunga; De Beer, Dalene; Riedel, Sylvia; Miller, Neil; Bowles, Sandra; Walczak, Beata; Muller, Christo; Joubert, Elizabeth
Mounting evidence of the ability of aspalathin to target underlying metabolic dysfunction relevant to the development or progression of obesity and type 2 diabetes created a market for green rooibos extract as a functional food ingredient. Aspalathin is the obvious choice as a chemical marker for extract standardisation and quality control, however, often the concentration of a single constituent of a complex mixture such as a plant extract is not directly related to its bio-capacity, i.e. the level of in vitro bioactivity effected in a cell system at a fixed concentration. Three solvents (hot water and two EtOH–water mixtures), previously shown to produce bioactive green rooibos extracts, were selected for extraction of different batches of rooibos plant material (n = 10). Bio-capacity of the extracts, tested at 10 μg ml−1, was evaluated in terms of glucose uptake by C2C12 and C3A cells and lipid accumulation in 3T3-L1 cells. The different solvents and inter-batch plant variation delivered extracts ranging in aspalathin content from 54.1 to 213.8 g kg−1. The extracts were further characterised in terms of other major flavonoids (n = 10) and an enolic phenylpyruvic acid glucoside, using HPLC-DAD. The 80% EtOH–water extracts, with the highest mean aspalathin content (170.9 g kg−1), had the highest mean bio-capacity in the respective assays. Despite this, no significant (P ≥ 0.05) correlation existed between aspalathin content and bio-capacity, while the orientin, isoorientin and vitexin content correlated moderately (r ≥ 0.487; P < 0.05) with increased glucose uptake by C2C12 cells. Various multivariate analysis methods were then applied with Evolution Program-Partial Least Squares (EP-PLS) resulting in models with the best predictive power. These EP-PLS models, based on all quantified compounds, predicted the bio-capacity of the extracts for the respective cell types with RMSECV values ≤ 11.5, confirming that a complement of compounds, and not aspalathin content alone, is needed to predict the in vitro bio-capacity of green rooibos extracts. Additionally, the composition of hot water infusions of different production batches of green rooibos (n = 29) at ‘cup-of-tea’ equivalence was determined to relate dietary supplementation with the extract to intake in the form of herbal tea.
Nutraceutical value of yellow- and red-fleshed South African plums (prunus salicina lindl.) : evaluation of total antioxidant capacity and phenolic composition
(MDPI, 2014) Venter, Alet; Joubert, Elizabeth; De Beer, Dalene
Ten South African plum cultivars and selections, including yellow- and redfleshed plums from two harvest seasons were evaluated in terms of nutraceutical value (phenolic composition, total polyphenol content (TPC) and total antioxidant capacity (TAC)) and fruit attributes (colour, fruit mass, etc.). Plums were evaluated at two maturity stages, i.e., directly after harvest (unripe) and after a commercial cold storage and ripening regime (ripe). The phenolic composition of South African plums varied greatly, both qualitatively and quantitatively, between cultivars and selections. Neochlorogenic acid, cyanidin-3-O-glucoside and quercetin-3-O-glucoside were the predominant hydroxycinnamic acid, anthocyanin and flavonol, respectively, although not present in all plums. The flavan-3-ols, (+)-catechin, (−)-epicatechin and procyanidins B1 and B2, were present in all plums. Red-fleshed plums tended to display higher TAC and TPC than yellow-fleshed plums. The flavan-3-ol content was highly correlated with TAC. The effect of harvest season was cultivar-dependent, but cultivar differences were not obscured. In terms of maturity stage, the ripe fruits tended to contain higher levels of anthocyanins and some flavonol compounds, although the TPC and TAC were not affected in most cases. South African plums, especially the red-fleshed selections PR04-32 and PR04-35, were shown to provide generally high TAC and TPC compared to literature values.
Short-term and sub-chronic dietary exposure to aspalathin-enriched green rooibos (Aspalathus linearis) extract affects rat liver function and antioxidant status
(MDPI, 2015-12-18) Van der Merwe, J. Debora; De Beer, Dalene; Joubert, Elizabeth; Gelderblom, Wentzel C. A.
An aspalathin-enriched green rooibos (Aspalathus linearis) extract (GRE) was fed to male Fischer rats in two independent studies for 28 and 90 days. The average dietary total polyphenol (TP) intake was 75.6 and 62.7 mg Gallic acid equivalents (GAE)/kg body weight (bw)/day over 28 and 90 days, respectively, equaling human equivalent doses (HEDs) of 12.3 and 10.2 GAE mg/kg bw/day. Aspalathin intake of 29.5 mg/kg bw/day represents a HED of 4.8 mg/kg bw/day (90 day study). Consumption of GRE increased feed intake significantly (p < 0.05) compared to the control after 90 days, but no effect on body and organ weight parameters was observed. GRE significantly (p < 0.05) reduced serum total cholesterol and iron levels, whilst significantly (p < 0.05) increasing alkaline phosphatase enzyme activity after 90 days. Endogenous antioxidant enzyme activity in the liver, i.e., catalase and superoxide dismutase activity, was not adversely affected. Glutathione reductase activity significantly (p < 0.05) increased after 28 days, while glutathione (GSH) content was decreased after 90 days, suggesting an altered glutathione redox cycle. Quantitative Real Time polymerase chain reaction (PCR) analysis showed altered expression of certain antioxidant defense and oxidative stress related genes, indicative, among others, of an underlying oxidative stress related to changes in the GSH redox pathway and possible biliary dysfunction.

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