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Evaluation of capillary electrophoresis for the analysis of indigenous tea phenolics
No full textThe endemic South African plant species, Aspalathus linearis (rooibos) and Cyclopia spp.
(honeybush) are consumed worldwide as popular herbal teas. In addition, recent trends in the
consumption of these products as ready-to-drink commodities and the use of extracts as ingredients in
food, beverage, cosmetic and nutraceutical products are partially ascribed to their potential healthpromoting
effects. Both rooibos and honeybush teas contain relatively high levels of rare antioxidative
phenolic compounds. The health properties of these plants are largely associated with their
content of phenolic compounds. The analysis of phenolics in these herbal teas is therefore important,
not only in support of fundamental research, but also for quality control and marketing purposes.
High performance liquid chromatography (HPLC) is the method of choice for the analysis of phenolic
compounds in natural products, due to the proven performance of the technique in terms of robustness
and sensitivity. However, HPLC also suffers from some drawbacks such as relatively high solvent
consumption, long analyses and challenges to obtain sufficient resolution for highly complex samples
such as these. Capillary electrophoresis (CE) is a potentially promising alternative technique for the
separation of phenolics. CE offers cheap routine analyses, high speed and high efficiencies and an
alternative separation mechanism compared to HPLC. The aim of this study was to evaluate CE as an
alternative to HPLC for the analysis of rooibos and honeybush tea phenolics.
Following extensive method optimisation, two capillary zone electrophoresis (CZE) methods which
provided efficient separation of the principal rooibos (15) and honeybush (8) tea phenolics, were
successfully developed for the first time. Experimental parameters evaluated and optimised include
the background electrolyte (BGE) composition and pH, capillary dimensions, analysis temperature,
applied voltage and injection volumes. A borate buffer was found to be essential due to the capability
of this BGE to form anionic complexes with phenolics containing vicinal diols, thereby affecting the
selectivity of the separation. The optimised BGE pHs for the rooibos and honeybush methods were
8.80 and 9.25, respectively, resulting in total analysis times (including conditioning of capillary) of 31
(honeybush) and 42 minutes (rooibos). Analysis times were slightly shorter than the routine HPLC
methods. The optimised CZE methods were characterised by alternative selectivity compared to
HPLC, and higher resolution of critical compound pairs was obtained. The methods were validated in
terms of repeatability of electrophoretic mobilities, linearity of calibration curves and sensitivity
(limits of detection (LODs) and limits of quantification (LOQs)). Sensitivity and repeatability of the
CZE methods were however not comparable with HPLC. Finally, the developed methods were
applied to the analysis of fermented and unfermented rooibos (Aspalathus linearis) and honeybush tea
(C. subternata and C. maculata samples). Quantitative data obtained for 10 samples of fermented and
unfermented rooibos and C. subternata and 9 of C. maculata each were compared to those obtained
by routine HPLC methods, and were found to be statistically comparable for the majority of
Stellenbosch University https://scholar.sun.ac.za
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compounds, with a few exceptions. The two quantitative CZE methods demonstrated their utility for
the routine quantitative analysis of phenolics in rooibos and honeybush teas, respectively, thereby
confirming the potential of CE as an alternative to HPLC for the routine analysis of these samples.National Research Foundatio
The effect of replacing electrolytic iron, in a multi-micronutrient fortification mix, with sodium iron (III) ethylenediaminetetraacetate (NaFeEDTA) on the sensory properties of porridge from maize meal
No full textIn developing countries, iron deficiency (ID) and the related iron deficiency anaemia (IDA) affects about 50 % of children and woman and about 25 % of men. In total, an estimated two billion people is affected worldwide. In developing countries, a typical diet is based on cereals, legumes and vegetables and these contain many iron inhibitors like phytic acid and polyphenols. Iron fortification of maize meal, a staple food in South Africa is regarded as a cost effective, sustainable way to improve iron status in that country. The replacement of electrolytic iron with sodium iron (III) ethylenediaminetetraacetate (NaFeEDTA) (a more bioavailable source of iron) in the current multi-micronutrient fortificant premix added to maize meal as an iron fortificant compound has the potential to greatly enhance the efforts to improve the iron status of populations consuming high-phytate cereal-based diets. However, poor consumer acceptance, unacceptable taste and discolouration of iron fortified foods have been frequently listed as causes of unsuccessful iron fortification programmes. This study evaluated the effects of replacing electrolytic iron (35 mg iron/kg maize meal) in a multi-micronutrient fortificant premix with NaFeEDTA (at 15 and 30 mg iron/kg maize meal) added to special maize meal on the colour (L* a* b*) and sensory properties (appearance and flavour) of stiff porridges. The porridges were prepared using three different types of cooking vessels (stainless steel, cast iron and aluminium pots) and was evaluated fresh (within 30 minutes of preparation) and after 24 hour refrigerated storage (3 - 5 oC). The porridges were subjected to analytical sensory evaluation to test for difference or similarity and a consumer acceptance test (n = 80 consumers). Electrolytic iron significantly reduced L* and a* colour values in fortified maize meal when compared to maize meal fortified with the multi-micronutrient mix excluding iron. Elemental iron powders (e.g. electrolytic iron) being black or dark grey powders may have caused slight darkening of cereal flours. The spot iron test showed a uniform distribution of iron in maize meal with NaFeEDTA 15 (fortified with 15 mg iron/kg maize meal), NaFeEDTA 30 (fortified at 30 mg iron/kg maize meal) and electrolytic iron as well commercially fortified maize meals. Electrolytic iron or NaFeEDTA 15 and 30 maize meals resulted in stiff maize porridge prepared in aluminium, cast iron and stainless steel having lower L* values when compared to porridge prepared from maize meal fortified with the multi-micronutrient premix excluding iron. This could be attributed to interaction between polyphenols (ferulic and p-coumaric acid) found in maize meal and iron ions (Fe2+/Fe3+). This interaction has been suggested to induce structural changes and polymerisation in the polyphenols and thereby influencing their light absorption pattern and thus leading to darkening of maize porridges. Cast iron cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge (fortified with premix excluding iron) in both appearance and flavour while stainless steel showed significant differences (p < 0.05) between iron treated porridges and control porridge only in flavour and aluminium cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge only in appearance. These differences could be attributed to the differences in thermal conductivity and heat transfer of the materials of the different cooking vessels and possible leaching of iron ions (Fe3+/Fe2+) from cast iron and stainless steel cookware and aluminium (Al3+) ions from aluminium cookware at different concentrations and/or rates during the cooking process. Appearance changes are probably due to the interaction between ion irons and polyphenols while flavour changes could be attributed to possible lipid oxidation of linoleic acid, a major polyunsaturated fatty acid found in maize meal. Iron ions (Fe3+/Fe2+) promotes lipid oxidation of linoleic acid leading to the development of hexanal, a major off-flavour compound in iron fortified maize meal porridge. Findings from this study indicate that a change from fortifying maize meal with electrolytic iron to NaFeEDTA will not lead to changes in appearance and flavour of maize porridge. However, an excess amount of NaFeEDTA (30 mg iron/kg maize meal) might lead to acceptability (taste) problems if porridge is prepared in cast iron cookware. Fortification of maize meal porridge with a more bioavailable source of iron (NaFeEDTA) may reduce the prevalence of iron deficiency in South Africa.National Research Foundatio
Design, construction and analysis of an alternative stroke rehabilitation device based on the principels of neuroplasticity
No full textThe use of robotics in post-stroke patient rehabilitation and research has increased
substantially during the last two decades. However, it has also led to important social and economic concerns, as the number of patients in developing
countries that can afford the expensive outpatient rehabilitation, and therefore be treated, are limited. Not much is known about alternative lowcost
rehabilitation devices. The motivation behind this thesis is to eventually address two of the most prominent limiting complications in stroke recovery
programs, which are the time available for patient engagement, and the cost
for outpatient rehabilitation. It presents the experimental design, construction,
and analysis of a prototype stroke rehabilitation device, based on the
principles of sensory stimulation therapy and neuroplasticity. The main objective
of this project was to come to the conclusion whether it is possible to
sense different electrobiological potentials in the brain during discrete events,
from the constructed wearable sensory feedback device. The device is experimentally
tested through the implementation of a case-control observational
Event-Related Potential (ERP) study on healthy test subjects. The experimental
results demonstrate the detection of cognitive and sensory-motor brain
activity in response to, and in anticipation of, a somatic sensation. Electroencephalography
(EEG) data is analyzed and decomposed to replicate three different
ERPs, namely the P200 exogenous-sensory and -visual component, and
the P300 endogenous component. The statistical analysis results indicate that
a definite correlation is found between the Visual vs. P200 (F = 1.274, p =
0.28535) and the P200 vs. P300 (F = 64.253; p < 0.001) components when
compared to previous ERP studies. The present evidence supports the use of mechanical-assisted therapy and indicates that potentially cost saving alternative
rehabilitation techniques are possible in their use of providing sensory
feedback, and recording and analyzing EEG feedback.National Research Foundatio
The influence of mycobacterium tuberculosis on B cells during disease and treatment response
No full textNational Research Foundatio
Monitoring compliance: NRF funded research outputs dissemination
No full textThe Grants Management and Systems Administration (GMSA) Directorate hosted its 7th annual Research Administrators Workshop (RAW) from 4 to 6 October 2016 in Polokwane. The workshop aimed to bring together key stakeholders from universities and science councils across South Africa, including international delegates, to share experiences and best practices in research administration and management
Cooperative prediction for cognitive radio networks
No full textCombining spectrum sensing (SS) and primary user (PU) traffic forecasting provides a cognitive radio network with a platform from which informed and proactive operational decisions can be made. The success of these decisions is largely dependent on prediction accuracy. Allowing secondary users (SU) to perform these predictions in a collaborative manner allows for an improvement in the accuracy of this process, since individual SUs may suffer from SS and prediction inaccuracies due to poor channel conditions. To overcome these problems a collaborative approach to forecasting PU traffic behaviour, that combines SS and forecasting through SU cooperation, has been proposed in this article. Both pre-fusion and post-fusion scenarios for cooperative prediction were investigated and a number of binary prediction methods were considered (including the authors’ own simple technique). Cooperative prediction performance was investigated, under various PU traffic conditions, for a group of ten SUs experiencing different channel conditions and a sub-optimal cooperative forecasting algorithm was proposed to minimise cooperative prediction error. Simulation results indicated that the accuracy of the prediction methods was influenced by the PU traffic pattern and that cooperative prediction lead to a significant improvement in prediction accuracy under most of the traffic conditions considered. However, this came at the cost of increased computational complexity. The pre-fusion scenario was found to be the most accurate scenario (up to 25 % improvement), but was also eleven times more complex than when no fusion was employed. The cooperative forecasting algorithm was found to further improve these results.National Research Foundation (South Africa
In vitro evaluation of metal chelators as potential metallo β-lactamase inhibitors.
No full textAims: This study aimed at investigating the use of metal chelators as potential metallo‐β‐lactamase inhibitors (MBL).
Methods and Results: The minimum inhibitory concentration (MIC) of meropenem was ascertained alone and in combination with various concentrations of macrocyclic (1,4,7‐ triazacyclononane‐1‐glutaric acid‐4,7‐diacetic acid = NODAGA) peptide derivatives and acyclic (N,N,N′,N′‐Tetrakis(2‐pyridylmethyl)ethylenediamine = TPEN and di‐(2‐picolyl)amine = DPA) metal chelators using the broth microdilution method. MICs of meropenem against carbapenem‐resistant enterobacteriaceae (CRE) producing MBLs were decreased to concentrations as low as 0•06 mg l−1 in the presence of some metal chelators. TPEN at 4 and 8 mg l−1 showed the best activity by decreasing meropenem MICs to 0•5 and 0•06 mg l−1, respectively, for some New Delhi Metallo‐beta‐lactamase (NDM) and Verona integron‐encoded metallo‐β‐lactamase (VIM) ‐producing enterobacteriaceae. DPA at 8 and 16 mg l−1 was also able to decrease meropenem MICs to 1 and 0•125 mg l−1, respectively, for these CREs. NODAGA peptide derivatives showed the least inhibition as 32 mg l−1 was required for meropenem MICs to be decreased to 0•06 mg l−1 against an NDM‐1 producing isolate.
Conclusion: The various metal chelators, TPEN, DPA and NODAGA peptide derivatives were able to inhibit the MBLs in decreasing order of activity, rendering CREs susceptible to meropenem.
Significance and Impact of the Study: In the absence of new antibiotics, this study evaluated metal chelators as potential MBL inhibitors.National Research Foundation (South Africa
Colistin and tigecycline resistance in carbapenemase producing Gram-negative bacteria: emerging resistance mechanisms and detection methods
No full textA literature review was undertaken to ascertain the molecular basis for tigecycline and colistin resistance mechanisms and the experimental basis for the detection and delineation of this resistance particularly in carbapenemase-producing Gram-negative bacteria. Pubmed, Google Scholar and Science Direct were searched with the keywords colistin, tigecycline, resistance mechanisms and detection methods. Trans-complementation and comparative MIC studies, mass spectrometry, chromatography, spectrofluorometry, PCR, qRT-PCR and whole genome sequencing (WGS) were commonly used to determine tigecycline and colistin resistance mechanisms, specifically modifications in the structural and regulatory efflux (acrAB, OqxAB, kpgABC adeABC-FGH-IJK, mexAB-XY-oprJM and soxS, rarA robA, ramRAB marRABC, adeLRS, mexRZ and nfxb) and lipid A (pmrHFIJFKLM, lpxA, lpxC lpxD and mgrB, pmrAB, phoPQ,) genes respectively. Mutations in the ribosomal 16S rRNA operon rrnBC, also yielded resistance to tigecycline through target site modifications. The mcr-1 gene conferring resistance to colistin was identified via WGS, trans-complementation and a murine thigh infection model studies. Common detection methods are mainly antibiotic sensitivity testing with broth microdilution while molecular identification tools are mostly PCR and WGS. Spectrofluorometry, MALDI-TOF MS, micro-array and real-time multiplex PCR hold much promise for the future as new detection tools.National Research Foundation (South Africa
Burrow architecture of the Damaraland mole-rat, (Fukomys damarensis) from South Africa
No full textThe burrow architecture (length, internal dimensions, fractal dimension of tunnel systems, number of nesting chambers and surface mounds) was investigated in the Damaraland mole-rat (Fukomys damarensis). A total of 31 animals were caught from five different colonies and their burrow systems were excavated in their entirety. The mean and SD colony size was 6 ± 3.3, with a range of 2–10 mole-rats. The sex ratio tended to be male biased 1.21:1. Males had a body mass of 80.5 ± 33.8 g, but were not significantly different to those of females, which had a mean body mass of 83.4 ± 24.9 g. The burrow system of the Damaraland mole-rats follows the same general architectural plan as recorded for other species of mole-rat with either one or two more centrally based, deeper, more permanent burrows that often connect to a nest area, which is used for resting and rearing offspring. The burrow systems contained several more superficial secondary tunnels at a shallower depth. The secondary tunnels accounted for up to 80% of the total burrow system. The mean length of the burrow system was 130 m and covered an area of 1 403 m2. The mean number of secondary branches in a burrow system was 10. The mean fractal dimension was 1.15, which implies the mole-rats do not explore their surrounding environment particularly efficiently when compared with that of other mole-rat species, but this may relate to the size of the main food resource, the Eland bean (Elephantorrhiza elephantina), which is randomly distributed and fed on in situ. Our study showed that colony size influences the size and complexity of the burrow system, with larger colonies having a longer burrow system covering a greater area with more secondary tunnels than that of smaller colonies.National Research Foundation (South Africa