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Many species within Combretaceae are traditionally used for the treatment of bacterial infections. The similarity in chemistry and antimicrobial activities within the family pose a challenge in selecting suitable species for herbal drug development.This study aimed at rapidly identifying antimicrobial compounds using bioautography-guided high-performance thin-layer chromatography coupled with mass spectrometry (HPTLC-MS).Hierarchical cluster analysis of ultra-performance liquid chromatography-mass spectrometry data from the methanol extracts of 77 samples, representing four genera within Combretaceae, was carried out. Based on groupings on the dendrogram, 15 samples were selected for bioautography analysis against four pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhimurium). Active compounds were identified using HPTLC-MS analysis of bands corresponding to the inhibition zones.Bioautography revealed 15 inhibition zones against the four pathogens, with the most prominent present for Combretum imberbe. Analysis of the active bands, using HPTLC-MS indicated that flavonoids, triterpenoids and combretastatin B5 contributed to the antibacterial activity. The compounds corresponding to molecular ions m/z 471 (Combretum imberbe) and 499 (Combretum elaeagnoides) inhibited all four pathogens, and were identified as imberbic acid and jessic acid, respectively. Chemotaxonomic analysis indicated that arjunic acid, ursolic acid and an unidentified triterpenoid (m/z 471) were ubiquitous in the Combretaceae species and could be responsible for their antibacterial activities.Application of HPTLC-MS enabled the rapid screening of extracts to identify active compounds within taxonomically related species. This approach allows for greater efficiency in the natural product research workflow to identify bioactive compounds in crude extracts.

This paper describes an investigation into the accumulation and distribution of Cu and Pb in Helichrysum splendidum, to assess the potential use of the plant in the phytoremediation of Cu- and Pb-contaminated soils. Plants of the same age were exposed to soils artificially contaminated with 10, 50, 100, 500 and 1000 mg/L Cu(II) and Pb(II). Although plant growth was not affected by the presence of Cu, high concentrations of Pb (> 500 mg/L) stunted the plants. Chlorophyll production was slightly reduced when plants were exposed to high concentrations of Cu (> 500 mg/L), whereas all the plants growing in Pb-contaminated soils indicated low levels of chlorophyll. Significant amounts of Cu and Pb were accumulated in the roots, with corresponding bioconcentration factors of > 1. Translocation of Cu to the shoots was restricted for plants growing in > 500 mg/L Cu-treated soils, whereas Pb was translocated to the shoots for all treatments, with translocation factors > 1. The Cu and Pb tolerance mechanism was ascribed to chelation and free radical scavenging, through the production of phenolic compounds. Helichrysum splendidum is able to adapt to and ameliorate soils contaminated with low to high levels of Cu(II) and Pb(II) and has potential for application in phytoextraction and phytostabilization of contaminated soils.

Helichrysum petiolare and Helichrysum odoratissimum, collectively known as ‘Imphepho’, are popular medicinal herbs that are indigenous to South Africa. The species are used interchangeably to relieve gastrointestinal and respiratory conditions, fever and urinary tract infections, implying that they produce antibacterial compounds. Although these herbs are sold in informal markets, they have not been commercialized. The aim of this study was to compare the chemical profiles and the antimicrobial activities of solvent extracts of the two species. The profiles of the smoke condensates were also compared, since the smoke from both species is inhaled during cultural rituals to induce central nervous system effects. After optimizing the extractant, the chemical profiles of aqueous methanol extracts of the aerial parts of twelve H. odoratissimum and fifteen H. petiolare samples, collected from several different localities, were obtained using ultra performance liquid chromatography-mass spectrometry (UPLC-MS). Three isomeric compounds were found to be present in both species. The construction of chemometric models from the data indicated a large degree of inter-population variation within H. odoratissimum, with the samples loosely clustering into two main groups. In contrast, the chemistry of H. petiolare was highly conserved. Discriminant analysis identified four distinguishing marker compounds for each species. One of the isomers common to both species, was isolated from H. odoratissimum and identified as 4,5-dicaffeoylquinic acid using nuclear magnetic resonance (NMR) spectroscopy, and is herein reported for the first time from the two species. Following validation of a developed UPLC-photodiode array (PDA) detection method, it was determined that the concentrations of the compound ranged from 3.89 - 31.1 µg/g in H. odoratissimum and from 2.3 to 13.4 µg/g in H. petiolare. High performance thin layer chromatography (HPTLC) fingerprints also indicated a greater degree of chemical variation within H. odoratissimum than in H. petiolare. This was confirmed through multivariate analysis of densitograms obtained from images of the fingerprints through the application of rTLC software, effectively mirroring the UPLC-MS results. The antibacterial activity of extracts of all the samples was determined using the minimum inhibitory concentration (MIC) serial dilution assay against selected Gram-positive (Staphylococcus saprophyticus, Enterococcus faecalis, Streptococcus agalactiae) and Gram-negative (Proteus mirabilis, Escherichia coli, Moraxella catarrhalis) pathogens that affect the urinary, respiratory and gastro-intestinal tracts. The MICs obtained for H. odoratissimum extracts indicated that these were more effective towards a larger range of bacteria than extracts of H. petiolare. The methanol extracts yielded average MICs denoting noteworthy or moderate activity towards three pathogens (E. coli, M. catarrhalis and S. agalactiae), while the chloroform:methanol extracts displayed noteworthy or moderate activity towards the same three pathogens, but also towards E. faecalis. These results justify to some degree the traditional use of H. odoratissimum to treat conditions of the gastro-intestinal, respiratory and urinary tracts. The UPLC-PDA profiles of smoke condensates of the two species, obtained under controlled conditions, revealed five major compounds that were common to both species. Although the similarity of the smoke profiles rationalises their interchangeable use for inhalation, the solvent extracts displayed little congruence regarding their chemical profiles or antibacterial activities.

Chromones are naturally occurring phenolic compounds that are universally present in a healthy human diet. To date, thousands of chromone derivatives, including chromone glycosides have been discovered, both from natural and synthetic origin. Many plant genera, including Aloe, Aquilaria, Cassia, Hypericum and Polygonum, are rich sources of chromones. Several genera of fungi, such as Aspergillus, Mycoleptodiscus, Orbiocrella, and Penicillium produce bioactive chromones. This class of compounds is mainly associated with anti-oxidant, antimicrobial, anticancer and anti-inflammatory activities. Various in vitro, in vivo and clinical studies have established the role of chromones in alleviating allergies, reducing oxidative damage, inhibiting cancer, infections and inflammation, and for treating neurological and psychiatric disorders. This review focuses mainly on natural chromones, and elaborates on their nutritional benefits, pharmacological activities, and mechanisms of action. Various scientific databases, including PubMed, Scopus and Google Scholar, were used to find relevant literature on chromones covering all available literature up to, and including the year 2019. This critical analysis of completed research regarding the nutraceutical properties of various chromone derivatives may provide new insight to scientists working in related fields.

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 B1 (FB1). The results demonstrated that FB1 exerts low cytotoxicity towards RTL-W1 cells without pH adjustment (IC50 1 746 μM), and no cytotoxicity after pH-adjustment to physiological conditions. The LC50 value for FB1 in the FET (1 058 μM at 48 h) confirmed low acute toxicity. Adjusting the pH to physiological conditions reduced the acute toxicity of FB1 towards zebrafish embryos, emphasising the importance of acidity/basicity of the medium in toxicity testing. Hydrolysed FB1 was less toxic than FB1 (LC50 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.

Acacetin (5,7-dihydroxy-4-methoxyflavone) is a naturally occurring flavonoid, known to possess numerous pharmacological properties, including neuroprotective, cardioprotective, anticancer, anti-inflammatory, antidiabetic, and antimicrobial activities. The molecule is widespread throughout the Plant Kingdom, but is particularly abundant in the Asteraceae, Euphorbiaceae, Passifloraceae, Lamiaceae and Malvaceae families. It has been shown to exhibit strong inhibitory effects against glutathione reductase, cyclo-oxygenase, acetylcholinesterase, aldose reductase and xanthine oxidase enzymes. A comprehensive overview of the potential therapeutic applications of acacetin was prepared after collating selected peer-reviewed papers, accessed from online scientific databases, specifically PubMed, Web of Science and Scopus. The mechanism of action, dose forms and structure-activity relationships of the molecule are some of the aspects discussed in the review, to facilitate further research and use of this molecule.

The National Research Foundation, the Department of Science and Technology of South Africa (through the SARChI initiative) as well as the South African Medical Research Council.

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 limit of detection to 2.4±1.2 µg/kg in sediments. Phthalates were present at average concentrations ranging from 0.023±0.041 to 2.1±1.5 μg/L and 20±0.63 to 55±6.9 µg/kg in water and sediments, respectively. The levels of OCPs and phthalates were greatest in autumn, attributed to higher input sources and concentration effects due to lower water levels. Phthalates were present at greater quantities at the inlet, while OCP accumulation was observed at the upper reaches of the dam. This may be an indication of the differences in input sources and translocation of these compounds, related to the topography of the dam and variability in water flow rates. These findings are important in highlighting the environmental and health concerns that may arise in the Olifants catchment area. After considering the outcomes of this study, we propose the implementation of regular and stringent monitoring strategies, which include surveys of OCPs and phthalates for Loskop Dam and similar water systems globally.

The South African Salvia species, Salvia africana-lutea, S. lanceolata and S. chamelaeagnea, are widely used to treat fever and inflammation associated with skin and lung infections. The aim of this study was to explore the non-volatile secondary metabolites and the phytochemical variation within these lesser known species, to support product development and commercialisation. Chemical profiles of the methanol extracts of 81 wild-harvested samples were obtained using ultra performance-quadrupole-Time-of-Flight-mass spectrometry (UPLC-qToF-MS). Forty-one compounds, including caffeic acid, rosmarinic acid, carnosol, carnosic acid and ursolic acid, were detected and confirmed across the three species. Nineteen compounds were tentatively identified of which 14 have not been reported in these species. Principal component analysis revealed distinct clusters corresponding to the three species, confirming chemical differences. Marker compounds for each species were revealed using orthogonal projection to latent structures-discriminant analysis. Further chemometric analysis reflected a degree of intraspecies variation, although the chemistry within populations was mostly conserved. Potential chemotypes for each species were identified through unique compounds associated with each group. The concentrations of medicinally important metabolites, namely, rosmarinic acid, carnosol, carnosic acid and ursolic acid, were determined, using validated UPLC-PDA methods. Ursolic acid was present at levels up to 38.2 mg/g, confirming that these species are a rich source of this compound. No similar studies combining liquid chromatography with chemometric analysis, and utilising a large sample size from various habitats, have been reported for these three Salvia species. The results will guide selection of cultivars with the best attributes for the intended therapeutic application, thereby protecting wild populations from over-exploitation.

Terminalia sericea is used throughout Africa for the treatment of a variety of conditions and has been identified as a potential commercial plant. The study was aimed at establishing a high-performance thin layer chromatography (HPTLC) chemical fingerprint for T. sericea root bark as a reference for quality control and exploring chemical variation within the species using HPTLC metabo3lomics. Forty-two root bark samples were collected from ten populations in South Africa and extracted with dichloromethane: methanol (1:1). An HPTLC method was optimized to resolve the major compounds from other sample components. Dichloromethane: ethyl acetate: methanol: formic acid (90:10:30:1) was used as the developing solvent and the plates were visualized using 10% sulfuric acid in methanol as derivatizing agent. The concentrations of three major bioactive compounds, sericic acid, sericoside and resveratrol-3-O-&beta, rutinoside, in the extracts were determined using a validated ultra-performance liquid chromatography-photodiode array (UPLC-PDA) detection method. The rTLC software (written in the R-programming language) was used to select the most informative retardation factor (Rf) ranges from the images of the analysed sample extracts. Further chemometric models, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were constructed using the web-based high throughput metabolomic software. The rTLC chemometric models were compared with the models previously obtained from ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). A characteristic fingerprint containing clear bands for the three bioactive compounds was established. All three bioactive compounds were present in all the samples, although their corresponding band intensities varied. The intensities correlated with the UPLC-PDA results, in that samples containing a high concentration of a particular compound, displayed a more intense band. Chemometric analysis using HCA revealed two chemotypes, and the subsequent construction of a loadings plot indicated that sericic acid and sericoside were responsible for the chemotypic variation, with sericoside concentrated in Chemotype 1, while sericic acid was more abundant in Chemotype 2. A characteristic chemical fingerprint with clearly distinguishable features was established for T. sericea root bark that can be used for species authentication, and to select samples with high concentrations of a particular marker compound(s). Different chemotypes, potentially differing in their therapeutic potency towards a particular target, could be distinguished. The models revealed the three analytes as biomarkers, corresponding to results reported for UPLC-MS profiling and thereby indicating that HPTLC is a suitable technique for the quality control of T. sericea root bark.

Artemisia afra (African wormwood) is a popular medicinal plant of southern Africa and is an excellent candidate for commercialisation. This current study was aimed at exploring the phytochemistry and chemical variation of non-volatile compounds within wild populations of A. afra, and developing chromatographic quality control protocols for raw materials based on the identification of marker compounds. Chromatographic data, from samples representing 12 distinct populations, were obtained using liquid chromatography-mass spectrometry. An untargeted chemometric approach revealed three clusters. Marker compounds for each cluster, revealed through discriminant analysis, were isolated and identified using NMR spectroscopy, as acacetin (1) (Group 1), chrysoeriol (2) (Group 2), and 3,5-di-O-caffeoylquinic acid (3) and scopoletin (4) (Group 3). In addition, (3) and rutin (5), (both reported for the first time from A. afra), and (1), (2), (4) and 4-caffeoylquinic acid (6) were established as reliable markers for species identification, since they were abundant in most samples. Quantitative analysis using a validated method established (4) as the dominant compound in the samples (1080–19,600 μg/g dry weight (d.w.)), followed by (5) (49.5–2490 μg/g d.w.). A high performance thin layer chromatography (HPTLC) method was developed. The Rf values and colours of the bands corresponding to the marker compounds were recorded so that these compounds could be easily identified for quality control purposes. Multivariate analysis of the data using the rTLC online application confirmed the presence of different chemical groupings within the samples. It was deduced that quantitative, rather than qualitative differences, characterised the samples. Future research should focus on comparing the efficacy of the various chemical clusters in multi-target biological assays aligned to the traditional use of the plant.

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 tested against Bacillus cereus (ATCC 11778), Staphylococcus epidermidis (ATCC 12223), Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 8739), Klebsiella pneumoniae (ATCC 13883), Pseudomonas aeruginosa (ATCC 27853), Shigella sonnei (ATCC 9292) and Salmonella typhimurium (ATCC 14028), using the minimum inhibition microdilution assay. Nine compounds, sericic acid, sericoside, resveratrol-3-O-&beta, rutinoside, ellagic acid, flavogallonic acid dilactone, methyl-flavogallonate, quercetin-3-(2&prime, &prime, galloylrhamnoside), resveratrol-3-(6&prime, galloyl)-O-&beta, d-glucopyranoside and arjunetin, were isolated from the root bark. All the compounds, with the exception of sericic acid, sericoside and resveratrol-3-O-&beta, rutinoside, were isolated for the first time from the root bark of T. sericea. Chemometric analysis revealed clustering that was not population specific, and the presence of three groupings within the samples, characterised by sericic acid, sericoside and an unidentified compound (m/z 682/4.66 min), respectively. The crude extracts from different populations displayed varied antibacterial activities against S. typhimurium (minimum inhibitory concentrations (MICs) 0.25&ndash, 1.0 mg/mL), but similar activity towards Bacillus cereus (1.0 mg/mL). Several compounds present in the root bark were highly active towards all or most of the pathogens tested, but this activity was not reflected by the chemical profiles of extracts prepared from the individual samples. Among the pure compounds tested, only flavogallonic acid dilactone and methyl-flavogallonate exhibited broad-spectrum activity. A biochemometric analysis indicated that there was no consistent association between the levels of phytochemicals and the activity of the active or non-active extracts. Although it was deduced that the major constituents of T. sericea root bark contributed to the chemotypic variation, further investigation of the interactions of compounds present in the root bark may provide antibacterial efficacies not evident when examining compounds singularly. The data reported herein will provide information that is fundamentally important for the development of quality control protocols.

In this study, the spatial and temporal variations in the levels of C8-C40 n-alkanes and 18 polycyclic aromatic hydrocarbons (PAHs) in water and sediment from Loskop Dam (Mpumalanga Province South Africa), were investigated between 2015 and 2017. In addition, their sources, which have not been well defined, were also studied over the period. This water body is sourced from a historically contaminated water body, the Olifants River, which flows through areas where a range of industrial and agricultural activities take place. Mass crocodile and fish mortalities have been recorded in this aquatic system, and contamination by organic pollutants were highlighted as a contributing factor. The total average n-alkane concentrations in water and sediments ranged from 0.574±00811 to 18.8±1.39 µg/L and 4760±243 to 30700±906 µg/kg, respectively. Similarly, PAHs were detected at total average concentrations of between 0.150±00494 and 49.8±6.86 µg/L in water and 61.6±5.95 to 2618±300 µg/kg. n-Alkane and PAH diagnostic ratios indicated a mixture of sources of these compounds, attributed to terrestrial, submerged and floating plant material, as well as petrogenic and pyrogenic combustion. Inlet, middle and upper segment site clustering was observed with non-metric multidimensional scaling (NMDS) and hierarchical cluster analysis (HCA), mainly driven by the prevalence of PAHs at the inlet sites and n-alkanes in the upper reaches. By using indicator compounds, the sources of contamination could be predicted. The strategy described here can be applied to any water body for continuous long-term monitoring of pollutant levels and to identify sources attributing to water pollution.

Sceletium tortuosum (Aizoaceae) is widely recognised for the treatment of stress, anxiety and depression, as well as for obsessive compulsive disorders. A comprehensive intraspecies chemotypic variation study, using samples harvested from two distinct regions of South Africa, was done using both proton nuclear magnetic resonance (1H-NMR) spectroscopy of methanol extracts (N = 145) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) of acid/base extracts (N = 289). Chemometric analysis of the 1H-NMR data indicated two main clusters that were region-specific (Northern Cape and Western Cape provinces). Two dimensional (2D) NMR was used to identify analytes that contributed to the clustering as revealed by the S-plot. The sceletium alkaloids, pinitol and two alkylamines, herein reported for the first time from S. tortuosum, were identified as markers that distinguished the two groups. Relative quantification of the marker analytes conducted by qNMR indicated that samples from the Northern Cape generally contained higher concentrations of all the markers than samples from the Western Cape. Quantitative analysis of the four mesembrine alkaloids using a validated UPLC-photo diode array (PDA) detection method confirmed the results of qNMR with regard to the total alkaloid concentrations. Samples from the Northern Cape Province were found to contain, on average, very high total alkaloids, ranging from 4938.0 to 9376.8 mg/kg dry w. Regarding the Western Cape samples, the total yields of the four mesembrine alkaloids were substantially lower (averages 16.4–4143.2 mg/kg). Hierarchical cluster analysis of the UPLC-MS data, based on the alkaloid chemistry, revealed three branches, with one branch comprising samples primarily from the Northern Cape that seemed somewhat chemically conserved, while the other two branches represented mainly samples from the Western Cape. The construction of an orthogonal projections to latent structures-discriminant analysis model and subsequent loadings plot, allowed alkaloid markers to be identified for each cluster. The diverse sceletium alkaloid chemistry of samples from the three clusters may facilitate the recognition of alkaloid profiles, rather than individual compounds, that exert targeted effects on various brain receptors involved in stress, anxiety or depression.

Athrixia phylicoides, known as “bush tea”, grows abundantly in South Africa. An infusion of the leaves is used as a beverage and to treat a multitude of health conditions. The aim of this study was to investigate the chemical variation within A. phylicoides and to identify characteristic compounds for quality control. Samples from 12 locations in South Africa were analysed using ultra-performance liquid chromatography. Hierarchical cluster analysis of the aligned ultra-performance liquid chromatography-time-of-flight mass spectrometry data indicated two groups on the resulting dendrogram, representing 48 samples. Five marker compounds, identified through visual inspection and the construction of a discriminant analysis model, were evident on the ultra-performance liquid chromatography-MS profiles. Four of these compounds were isolated and identified, three as hydroxy methoxyflavones and the fourth as a coumarate, using nuclear magnetic resonance spectroscopy. An ultra-performance liquid chromatography-photodiode array method was developed and validated for the determination of the marker compounds using the isolates as standards. The limits of detection for the four compounds ranged from 0.92 – 2.50 µg/mL. Their recoveries at three concentration levels (1.00, 10.0, and 100 µg/mL) were between 97.0 and 101%, while acceptable intra- and inter-day precision was obtained as reflected by percentage relative standard deviation values below 2.24%. The concentrations of all the marker compounds were found to be higher in samples corresponding to Group 1 of the dendrogram than in those from Group 2. This may be attributable to differences in altitude, climate, and some edaphic factors. Identification of these marker compounds will make a valuable contribution towards the quality control and sustainable commercialisation of bush tea.

Chemical interrogation of the Sceletium genus and Amaryllidaceae family of plants has yielded a diverse array of aryl-hydroindole containing alkaloids. Included in this class is channaine, which was tentatively identified, without comprehensive structural elucidation from Sceletium tortuosum in 1957. Following its isolation from S. strictum, the structure of channaine was eventually resolved by X-ray crystallographic analysis, which revealed an unusual cage-like ring structure at the interface of two aryl-hydroindole subunits. However, since this report in 1978, channaine has not re-appeared in the literature. In this letter, the full NMR characterisation of channaine, isolated from S. tortuosum collected from St Helena in the Western Cape Province of South Africa, is reported for the first time.

Consumption of a refreshing beverage prepared from the dried leaves and twigs of Athrixia phylicoides, commonly referred to as bush tea, is widespread in South Africa. The tea has an illustrious history of use by the indigenous people of southern Africa and has the potential for commercialisation. Several ethnic groups use decoctions and pastes prepared from the plant to treat a multitude of unrelated conditions. This review is aimed at providing a comprehensive overview of the ethnopharmacology, phytochemistry, biological activities, toxicity and commercial aspects of A. phylicoides. Books, containing botanical and ethnopharmacological information were extensively consulted, and electronic databases were searched to acquire relevant articles, with no specific time frame set. Although the majority of the traditional uses indicate that A. phylicoides has strong antimicrobial properties, this is not well supported by scientific data, suggesting that more research is required involving more pathogens and the investigation of a potential alternative mode of action. The secondary metabolites of the plant have been extensively explored and several sesquiterpenes, coumarins, flavonoids and phenol carboxylic acids have been identified. However, there is a paucity of information regarding the chemical variation within the species. A multidisciplinary metabolomic approach involving sophisticated and information-rich technologies, in combination with multivariate analysis, should be undertaken to record chemotypic variation and to identify potential biomarker compounds for quality control. Some of the ethnobotanical uses have been supported through scientific studies, but a window of opportunity exists to contribute data on the pharmacological activities. Despite efforts to facilitate the commercialisation of bush tea in South Africa in an effort to grow the bio-economy of the region, more fundamental research is required to ensure the sustainability and expansion of such an industry. The commercialisation of rooibos and honeybush tea in South Africa is underpinned by basic and applied research and serves as appropriate models for the development of the bush tea industry.

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.

The combustion of coal in thermal power plants may result in high concentrations of elements in the coal fly ash remaining that may be toxic to living organisms or pose a risk to the environment. This study was aimed at determining the concentrations of potentially toxic elements in coal fly ash leachates, in an attempt to simulate natural processes that influence the environment. Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and elemental composition studies were employed to characterize the physicochemical properties of the parent coal fly ash. The effect of various leaching parameters, including the pH of leaching solutions, the volume ratio of leaching solutions to the mass of coal fly ash, leaching time and temperature, were investigated. Moreover, the kinetics of the leaching of toxic elements from coal fly ash was also investigated by considering that the leaching process is governed by dissolution. Zero order, pseudo-first order, pseudo-second order, power function, simple Elovich and parabolic diffusion kinetic models were used to evaluate the leaching process. The experimental results indicate that the pH and leaching time had the most significant effect on the leaching behavior of elements from coal fly ash.

Many mines in South Africa were inappropriately closed and left unattended during the last century. These old mines are potential sources of environmental pollution and may pose a health risk to local populations, since the surrounds contain elevated levels of toxic elements. Soil from the old Edendale lead mine property in Mamelodi Extension 11, east of Pretoria, which was suspected to be contaminated with lead, was analysed. The mine, which primarily extracted galena, was decommissioned in 1938. During this study, the old mine property and surrounds were screened for zinc and lead using a field-portable X-ray fluorescence (pXRF) spectrometer. The metal concentrations, which ranged from 18 to 7 300 mg/kg for zinc and from 50 to 21 000 mg/kg, for lead, were plotted together with the GPS coordinates to produce a concentration distribution map for lead and zinc. This map revealed three anomalies of unacceptably high concentrations, possibly corresponding to areas where ore had been piled or dumped to waste from the old mine. Thirty-six of the soil samples that were analysed by pXRF on site were selected and analysed in the laboratory using inductively coupled plasma-optical emission spectrometry (ICP-OES) for verification purposes. The zinc and lead concentrations obtained from the two analytical methods were compared using linear regression analysis. Excellent correlation was obtained between the results from the two methods (r² = 0.99 for zinc and r2 = 0.95 for lead).

Ethnopharmacological relevance Many species within the family Combretaceae are popular medicinal plants that are used traditionally to treat various conditions, of which many are related to bacterial infections. Global concerns regarding the increasing resistance of pathogens towards currently available antibiotics have encouraged researchers to find new drugs with antibacterial activity, particularly from plant sources. Aim of the study This study was aimed at exploring the broad-spectrum antibacterial potential of methanol extracts of species representing four genera of Combretaceae (Combretum, Pteleopsis, Quisqualis, Terminalia), indigenous to South Africa, using a biochemometric approach. Materials and methods The microdilution assay was used to determine the antibacterial activities, measured as minimum inhibitory concentrations (MICs), of the 51 methanol extracts representing 35 Combretaceae species, against nine species of pathogenic bacteria. Integrative biochemometric analysis was performed, thereby correlating the MIC values with the metabolomic data obtained from ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Orthogonal projections to latent structures-discriminant analysis (OPLS-DA) models were constructed for six pathogens displaying variation in their susceptibility towards the extracts. Results Evaluation of the overall MIC values obtained indicated that extracts of species from the four genera displayed the highest activity towards Bacillus cereus ATCC 11778 (average MIC 0.52 mg/mL) and Salmonella typhimurium ATCC 14028 (average MIC 0.63 mg/mL). These bacteria were the most sensitive Gram-positive and Gram-negative bacteria, respectively. Extracts from Combretum acutifolium, Combretum imberbe and Combretum elaeagnoides were the most active, with average MIC values of 0.70 mg/mL, 0.52 mg/mL and 0.45 mg/mL, respectively. Five triterpenoid compounds were tentatively identified as biomarkers from the biochemometric analysis. Conclusion Correlation of the phytochemistry of species from four genera in the Combretaceae family with antibacterial activity revealed that triterpenoids are responsible for the broad-spectrum antibacterial activity observed.

Rivers feeding into the Loskop Dam, South Africa, pass through coal mining and heavily industrialised areas. Previous studies investigating mass mortalities of crocodile and fish in the river system, revealed the presence of organic compounds, including polycyclic aromatic hydrocarbons (PAHs), in their tissues. Samples were collected from nine sites within the dam in winter and summer. Liquid-liquid and microwave-assisted extraction was used for preconcentrating PAHs from water and sediment samples, respectively. Extracts were analysed by gas chromatography-mass spectrometry in the selected ion monitoring mode to determine the presence and levels of the 16 United States Environmental Protection Agency (US EPA)-priority PAHs. Significant levels of PAHs were found in both water and sediment samples. Concentrations were higher in sediments than in water, as well as in samples collected in winter. Levels of PAHs in sediments were generally higher than those reported by many researchers for other water bodies in industrialised areas. Zebrafish embryos were used to assess potential risks associated with the water and sediment, and to determine the effects of PAHs on aquatic life. Embryos, exposed to intact water and sediment samples, as well as to diluted sediment extracts, were monitored for 120 h post fertilisation. Sediment proved more toxic to zebrafish embryos than water, causing delayed embryo development and malformations. These findings are alarming as they indicate that this water system is under stress. These findings can be typical of any water system situated in a coal mining and industrial region.

The volatile constituents of nine liverworts species ( Asterella marginata , Dumortiera hirsuta , Fossombronia swaziensis , Marchantia pappeana , Marchantia polymorpha subsp. ruderalis , Pallavicinia lyellii , Plagiochasma rupestre , Riccia albolimbata and Symphyogyna podophylla ) from South Africa were determined by gas chromatography. Where possible the volatile constituents identified were compared to those reported for the same species from other countries. Among the analysed liverworts, the chemical compositions of A. marginata , F. swaziensis , M. pappeana , and R. albolimbata are reported for the first time. Each of the analysed liverwort species produced its own characteristic components. Thujopsanes, chamigranes and cuparanes were found to be the most characteristic components of M. polymorpha subsp. ruderalis . The presence of dumortane-type sesquiterpenoids in D. hirsuta indicated that this species is similar in chemistry to an Argentinean sample. This is one of only a handful of reports on the presence of this sesquiterpene-type in liverworts. Simple thallose liverworts, S. podophylla and P. lyellii , were characterized by the presence of labdane-type diterpenoids. In addition, the antimicrobial activities of chloroform:methanol (1:1) extracts of the liverworts were evaluated against several important human pathogens using the serial dilution assay. Four of the liverwort species were active against Pseudomonas aeruginosa with MIC values ranging from 0.50 to 1.0 mg/mL. Some activity (MIC value of 1.0 mg/mL) was also recorded for the crude extracts of P. lyellii and M. pappeana against Escherichia coli. The extract of S. podophylla displayed the best activity towards the yeast Cryptococcus neoformans (MIC = 1.0 mg/mL). Although approximately 300 liverwort species occur in southern Africa, a Scopus search confirmed that this is the first report of the volatile profiles and biological properties of species from the region.