Papers by Sandra Combrinck
Phytochemistry, 2021
Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) is a natural anthraquinone derivative that is pr... more Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) is a natural anthraquinone derivative that is present in numerous globally renowned herbal medicines. It is recognised as a protein tyrosine kinase inhibitor and as an anticancer drug, active against various tumour cells, including lung, breast, liver, and ovarian cancer cells. Recently, its role in combination chemotherapy with various allopathic medicines, to minimize their toxicity and to enhance their efficacy, has been studied. The use of emodin in these therapies is gaining popularity, due to fewer associated side effects compared with standard anticancer drugs. Emodin has a broad therapeutic window, and in addition to its antineoplastic activity, it displays anti-ulcer, anti-inflammatory, hepatoprotective, neuroprotective, antimicrobial, muscle relaxant, immunosuppressive and antifibrotic activities, in both in vitro and in vivo models. Although reviews on the anticancer activity of emodin have been published, none coherently unite all the pharmacological properties of emodin, particularly the anti-oxidant, antimicrobial, antidiabetic, immunosuppressive and hepatoprotective activities of the compound. Hence, in this review, all of the available data regarding the pharmacological properties of emodin are explored, with particular emphasis on the modes of action of the molecule. In addition, the manuscript details the occurrence, biosynthesis and chemical synthesis of the compound, as well as its toxic effects on biotic systems.
Water SA, 2021
Organochlorine pesticides (OCPs) and phthalates are amongst the most emphasized man-made environm... more Organochlorine pesticides (OCPs) and phthalates are amongst the most emphasized man-made environmental contaminants, due to their prevalence, persistence and potential to induce adverse effects in organisms. In addition to prevailing industrial and domestic activities, their presence in the environment is exacerbated by leaching from associated materials, run-off and emissions. The Loskop Dam in the Mpumalanga Province, South Africa, is located on the Olifants River, which flows through a hub of industrial and agricultural activities. Research aimed at monitoring the levels of OCPs and phthalate contamination in South Africa, particularly in the Olifants catchment, has been limited and is restricted to short-term monitoring. In this study, the spatial and temporal variations of 21 OCPs and 7 phthalates in water and sediments from Loskop Dam were evaluated over a 3-year period (2015–2017). Annual average OCP levels ranged from 0.013±0.006 to 0.36±0.13 μg/L in water and from below the...
Fitoterapia, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
SSRN Electronic Journal, 2021
Fitoterapia, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Molecules, 2020
Terminalia sericea Burch. ex. DC. (Combretaceae) is a popular remedy for the treatment of infecti... more Terminalia sericea Burch. ex. DC. (Combretaceae) is a popular remedy for the treatment of infectious diseases. It is widely prescribed by traditional healers and sold at informal markets and may be a good candidate for commercialisation. For this to be realised, a thorough phytochemical and bioactivity profile is required to identify constituents that may be associated with the antibacterial activity and hence the quality of raw materials and consumer products. The aim of this study was to explore the phytochemistry and identify the antibacterial constituents of T. sericea root bark, using a metabolomic approach. The chemical profiles and antibacterial activities of 42 root bark samples collected from three districts in the Limpopo Province, South Africa, were evaluated. Dichloromethane:methanol (1:1) extracts were analysed using ultraperformance liquid chromatography (UPLC)-mass spectrometry (MS), and chemometric models were constructed from the aligned data. The extracts were test...
Journal of Applied Research on Medicinal and Aromatic Plants, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Toxicology Letters, 2019
Fumonisins are common contaminants of maize. The neutral red assay, using the RTL-W1 trout liver ... more Fumonisins are common contaminants of maize. The neutral red assay, using the RTL-W1 trout liver cell line, and the fish embryo test (FET), using zebrafish, were selected to assess the effect of pH on the cytotoxicity, acute toxicity and teratogenicity of fumonisin B 1 (FB 1). The results demonstrated that FB 1 exerts low cytotoxicity towards RTL-W1 cells without pH adjustment (IC 50 1 746 μM), and no cytotoxicity after pH-adjustment to physiological conditions. The LC 50 value for FB 1 in the FET (1 058 μM at 48 h) confirmed low acute toxicity. Adjusting the pH to physiological conditions reduced the acute toxicity of FB 1 towards zebrafish embryos, emphasising the importance of acidity/basicity of the medium in toxicity testing. Hydrolysed FB 1 was less toxic than FB 1 (LC 50 2 690 μM at 48 h), and neither were teratogenic towards zebrafish embryos. Results confirm that the FET may account for effects not observable in cell cultures.
Australasian Plant Pathology, 2016
Mango blossom malformation, caused by infection of mango panicles and young shoots by Fusarium sp... more Mango blossom malformation, caused by infection of mango panicles and young shoots by Fusarium species, leads to significant reductions in fruit yield. Previously, chemometric models were established that allowed biomarkers associated with resistance in tolerant cultivars to be identified. High concentrations of these biomarkers, mangiferin, maclurin and maclurin O-galloyl-glucoside, are inherent genetic traits of some cultivars and have been linked to their ability to confine Fusarium infection. In this study, phenolic profiles of mature leaf extracts from cultivars exhibiting different levels of resistance to Fusarium infection were obtained by UPLC-Q-ToF x MS, five tolerant and seven susceptible cultivars. A robust prediction model, was developed that could be used throughout the season to predict the likelihood of new cultivars being susceptible or tolerant towards mango malformation disease. The levels of biomarkers revealed by the models in tolerant and susceptible cultivars were compared and significant differences were observed. These models can serve as an important tool to investigate appropriate cultivars, prior to their introduction to areas prone to the disease.
Journal of Ethnopharmacology, 2016
Ethnopharmacological relevance Khat, the leaves of Catha edulis, is used as a "natural amphetamin... more Ethnopharmacological relevance Khat, the leaves of Catha edulis, is used as a "natural amphetamine-like" stimulant in eastern and southern Africa, as well as in the Arabian Peninsula. Leaves are masticated to elicit a state of euphoria. Although the psychostimulatory effects of the leaves are attributed to the presence of phenylpropylamino alkaloids (i.e. cathinone, cathine and norephedrine) the extent of permeation of these alkaloids across the oral and intestinal mucosa has not been established. Materials and methods Cathinone was isolated in the form of the oxalate salt from young buds, following acid-base extraction. High performance countercurrent chromatography (HPCCC) was used to isolate cathine and norephedrine, following borohydride reduction of a mixture of the three alkaloids. The in vitro permeability of these three alkaloids in their pure form, as well as in a crude extract, was evaluated across Caco-2 cell monolayers and across excised porcine intestinal, sublingual and buccal tissues. Results The purities of the isolated cathine and norephedrine were in excess of 90%, thereby proving that HPCCC can be applied for efficient separation of these alkaloids from extracts of Khat. The apparent permeability (P app) coefficients for the Khat alkaloids in their pure form were all above 1.0 × 10 −6 cm/s, indicating that the transport of the three alkaloids across the selected biological membranes is comparable to that of the highly permeable reference compound, caffeine. Although readily transported across the various membranes, the alkaloids were transported to a lesser extent when present in a leaf extract, suggesting that other phytochemicals present in the extract influence their permeation. Conclusions These results provide evidence that chewing of Khat contributes to the buccal and sublingual absorption of the psychoactive alkaloids in the bloodstream directly across the oral mucosal membranes. In addition, it confirms that these metabolites will be readily absorbed from the gastrointestinal tract when swallowed.
Journal of pharmaceutical and biomedical analysis, Jan 12, 2016
Henna (Lawsonia inermis) is applied to stain keratin, present in hair, skin and fingernails, a re... more Henna (Lawsonia inermis) is applied to stain keratin, present in hair, skin and fingernails, a red-orange or rust colour. Producers of temporary tattoos mix the aromatic amine compound, para-phenylenediamine (PPD) into natural henna to create 'black henna' that rapidly stains the skin black. However, PPD may cause severe delayed hypersensitivity reactions following skin contact. This study proposes a rapid direct-analysis method to detect and identify PPD using an atmospheric solids analysis probe (ASAP) coupled to a Q-ToF mass spectrometer (MS). Since laborious, multistep methods of analysis to determine PPD are undesirable, due to the instability of the compound in solution, a screening method involving no sample preparation steps was developed. Experiments were carried out to optimise the corona current, sample cone voltage, source temperature, and desolvation gas temperature to determine ideal ASAP-Q-ToF-MS analysing conditions. Eleven of the 109 henna samples, originati...
Analytical Letters, 2016
ABSTRACT Forty-nine green coffee (Coffea arabica L.) bean samples, representing the Harar, Jimma,... more ABSTRACT Forty-nine green coffee (Coffea arabica L.) bean samples, representing the Harar, Jimma, Kaffa, Wollega, Sidama, and Yirgachefe varieties from east, west, and south Ethiopia were analyzed for Mg, P, S, Ca, Mn, Fe, Cu, Ba, Si, and K using inductively coupled plasma-optical emission spectroscopy. Principal component analysis was used to group the samples based on their elemental compositions. Application of linear discriminant analysis provided models with an accuracy of 92% for region of production and 79% for variety. The elements P, Mn, S, Cu, and Fe were the most discriminating elements. These results show that initial screening may be performed to characterize possible fraudulently labelled products with verification by the existing paper-based traceability system and sensory evaluation.
Chemistry for first year students has been identified by Tshwane University of Technology as one ... more Chemistry for first year students has been identified by Tshwane University of Technology as one of the subjects with a low pass rate. It is apparent that students often memorize formulae and definitions, without understanding the underlying concepts required to work with abstract units of measure. We have found that the majority of students at this university are unable to balance reaction equations satisfactorily. They are also unable to predict the reaction yield, or identify limiting reagents. It is imperative that these and other related problems are overcome before any meaningful change to the high failure rate at first year level will be realized. All conventional forms of lecture presentation failed to make any significant impact on the success rate. Structured worksheets were developed and used, together with tactile models, to address the problems and the initial findings showed a marked improvement. It was discovered that the students' problems originated from their inability to understand the meaning of subscripts and coefficients in chemical equations. The worksheets and the impact they have made on the students' understanding of stoichiometry are shared in this paper.
Biomedical Chromatography, 2015
A molecularly imprinted polymer (MIP) was prepared using (−)‐norephedrine as the template, methac... more A molecularly imprinted polymer (MIP) was prepared using (−)‐norephedrine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker and chloroform as the porogen. The MIP was used as a selective sorbent in the molecularly imprinted solid‐phase extraction (MIP‐SPE) of the psychoactive phenylpropylamino alkaloids, norephedrine and its analogs, cathinone and cathine, from Khat (Catha edulis Vahl. Endl.) leaf extracts prior to HPLC‐DAD analysis. The MIP was able to selectively extract the alkaloids from the aqueous extracts of Khat. Loading, washing and elution of the alkaloids bound to the MIP were evaluated under different conditions. The clean baseline of the Khat extract obtained after MIP‐SPE confirmed that a selective and efficient sample clean‐up was achieved. Good recoveries (90.0–107%) and precision (RSDs 2.3–3.2%) were obtained in the validation of the MIP‐SPE‐HPLC procedure. The content of the three alkaloids in Khat sampl...
Vibrational Spectroscopy, 2015
Abstract The leaves of Catha edulis Vahl. Endl., known as Khat, are widely used as a “natural amp... more Abstract The leaves of Catha edulis Vahl. Endl., known as Khat, are widely used as a “natural amphetamine” stimulant in Africa and in the Arabian Peninsula. In recent years, there has been an increase in the amounts exported to the USA, Australia and Europe. Although the dried, powdered form of the young and mature leaves, as well as samples from different geographical origins, have similar physical appearance, they have not been proven to exhibit equipotent stimulatory activity. In this study, powdered young and mature leaves were differentiated using vibrational spectroscopy, which included mid-infrared (MIR) and near-infrared (NIR) spectroscopy and hyperspectral imaging (HSI), and ultra performance liquid chromatography-mass spectrometry (UPLC–MS), in combination with chemometric data analysis. Samples originating from Ethiopia or South Africa could also be distinguished using chemometric models constructed from HSI data. Principal component analysis (PCA) and orthogonal projection to latent structures discriminant analysis (OPLS-DA) was successfully applied to classify powdered Khat samples according to their geographical origin and level of maturity. The OPLS-DA model constructed from the MIR and UPLC–MS data displayed the ability to clearly distinguish between young and mature leaves, as illustrated by the model statistics ( R 2 X cum and Q 2 cum > 80% and R 2 Y > 90%). Shortwave infrared hyperspectral imaging could distinguish Khat samples from two distinct geographical regions with good model statistics ( R 2 X cum = 0.91 and Q 2 cum = 0.92) and discriminate between the maturity levels ( R 2 X cum = 0.85 and Q 2 cum = 0.80). These models could prove valuable as rapid techniques for identifying confiscated Khat in forensic environments.
VIII International Mango Symposium, 2009
Cultivar dependant discolouration of mango lenticels is a well-known phenomenon. This discolourat... more Cultivar dependant discolouration of mango lenticels is a well-known phenomenon. This discolouration is often the reason export fruit are downgraded. Tissue surrounding lenticels progressively becomes affected, but the manifestation and severity of the condition can be unpredictable. Previous research to find and control the trigger of the condition included studies of horticultural aspects, and preand postharvest processes. However, with no satisfactory solution apparent, a study of the lenticel morphology and its related chemistry, and the epicuticular wax were undertaken. Three commercially important cultivars from South Africa, 'Keitt', 'Kent' and 'Tommy Atkins', each with a distinctly different level of affliction were used in this study. From the combined results of high performance liquid chromatography and microscopy, several new aspects were elucidated. Cultivars have a structural relationship to discolouration, while chemical profiling and ultrastructural studies of lenticels pointed towards physiological irritation as the stimulus for the development of the condition.
Phytochemistry, 2015
Gingerols are the major pungent compounds present in the rhizomes of ginger (Zingiber officinale ... more Gingerols are the major pungent compounds present in the rhizomes of ginger (Zingiber officinale Roscoe) and are renowned for their contribution to human health and nutrition. Medicinal properties of ginger, including the alleviation of nausea, arthritis and pain, have been associated with the gingerols. Gingerol analogues are thermally labile and easily undergo dehydration reactions to form the corresponding shogaols, which impart the characteristic pungent taste to dried ginger. Both gingerols and shogaols exhibit a host of biological activities, ranging from anticancer, anti-oxidant, antimicrobial, anti-inflammatory and anti-allergic to various central nervous system activities. Shogaols are important biomarkers used for the quality control of many ginger-containing products, due to their diverse biological activities. In this review, a large body of available knowledge on the biosynthesis, chemical synthesis and pharmacological activities, as well as on the structure-activity relationships of various gingerols and shogaols, have been collated, coherently summarised and discussed. The manuscript highlights convincing evidence indicating that these phenolic compounds could serve as important lead molecules for the development of therapeutic agents to treat various life-threatening human diseases, particularly cancer. Inclusion of ginger or ginger extracts in nutraceutical formulations could provide valuable protection against diabetes, cardiac and hepatic disorders.
International Journal of Phytoremediation, 2015
Contamination of soils with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, Research ... more Contamination of soils with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, Research Department Explosive) as a result of military applications is a large-area problem globally. Since coniferous trees dominate the vegetation of large areas of military land in Central Europe, particularly in Germany, the long-term fate of 14 C-RDX in the conifers Scots pine and Dwarf Alberta spruce was studied. Acetic acid was the most effective solvent for the removal of extractable RDX residues from homogenates of RDX-laden tree material (85%, 80-90% and 64-80% for roots, wood and needles, respectively). On average, only a fifth of RDX-derived 14 C was bound in nonextractable residues (NER). Within the main cell wall compartments, lignin was the dominant binding site for NER (needles: 32-62%; roots: 38-42%). Hemicellulose (needles: 11-18%; roots: 6-11%) and cellulose (needles: 12-24%; roots: 1-2%) were less involved in binding and a considerable proportion of NER (needles: 15-24%; roots: 59-51%) was indigestible. After three-year incubation in rot chambers, mineralisation of tree-associated 14 C-RDX to 14 CO 2 clearly dominated the mass balance in both tree species with 48-83%. 13-33% of 14 C-RDX-derived radioactivity remained in an unleachable form and the remobilisation by water leaching was negligible (< 2%).
Phytochemistry Letters, 2014
Hypoxis species (Hypoxidaceae) are amongst the most widely used medicinal plants in southern Afri... more Hypoxis species (Hypoxidaceae) are amongst the most widely used medicinal plants in southern Africa. Although the phytochemistry of Hypoxis hemerocallidea has been extensively investigated, little is known regarding the secondary metabolites of the other indigenous species, including Hypoxis colchicifolia and Hypoxis galpinii. Two new phenolic glycosides, 3-hydroxy-4-O-b-D-glucopyranosylbenzaldehyde and 1,5-bis(3,4-dihydroxyphenyl)-1,2-dihydroxy-4-pentyne-2-p-coumaroyl-b-D-glucopyranoside were isolated from corms of H. colchicifolia and H. galpinii, respectively. The norlignan glycosides (hypoxoside, dehydroxy hypoxoside and bis-dehydroxy hypoxoside) were isolated from H. colchicifolia for the first time, using high performance countercurrent chromatography and elucidated by 1D and 2D NMR as well as high resolution MS. In addition, geraniol glycoside and b-sitosterol, previously described in Hypoxidaceae, were isolated from the same species. The presence of hypoxoside in all three species investigated indicated that the interchangeable use of Hypoxis species by communities has some merit. Establishing the biological properties of the new constituents will provide more insight into the medicinal value of the genus.
Journal of Ethnopharmacology, 2014
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Papers by Sandra Combrinck