Thesis (M. A. (African languages)) -- University of Limpopo, 2015

Thesis (MSc. (Biochemistry)) -- University of Limpopo, 2017 / The malignancy of cancer cells is responsible for the high death rate in patients diagnosed with metastatic cancers. Medicinal plants represent a reservoir of bioactive compounds that can be useful in the management of cancer. In this study, semi-purified extracts of Ricinus communis leaves were evaluated for their potential to serve as an anti-metastatic agent by using in vitro assays that tested their effects on a number of processes related to metastasis. The exhaustive extraction procedure was employed to generate the crude acetone extracts of R. communis leaves. The crude extracts were then subjected to solvent-solvent fractionation to yield six semi-purified extracts (n-butanol, Chloroform, Ethyl-acetate, n-hexane, Methanol + H2O and H2O). Thin layer chromatography (TLC) was done to determine the phytochemical composition of the semi-purified extracts as well as their antioxidant potential. Non-polar fractions showed to have a diverse mixture of phytochemicals with, however, very limited antioxidant activity. On the other hand, polar fractions showed to have phytochemical compounds with strong antioxidant potential. TLC guided the selection of n-hexane and n-butanol as fractions of great phytochemical diversity and antioxidant activity, respectively. The selected fractions were then assessed for their effect on the viability of normal fibroblasts (BUD-8) and breast (MCF-7) cancer cells using the MTT assay. The n-butanol fraction was shown to significantly decrease the viability of BUD-8 at concentrations above 200 µg/ml. The n-hexane fraction, however, showed to significantly affect the viability of the cells even at lower concentrations. On the positive side, the reduced viability of BUD-8 cells after exposure to both fractions was followed by an increase in cell proliferation after 24 hours suggesting that the extracts exhibited cytostatic rather than cytotoxic effects. Treatment of MCF-7 cells with different concentrations (100-500 µg/ml) of the fractions showed a dose- and time-dependant decrease in cell viability. Hoechst stain also confirmed the non-toxicity of the fractions to MCF-7 cells at 100 and 200 µg/ml. The fractions also showed to possess free radical scavenging activities by reducing the amount of intracellular ROS as demonstrated by the DCFH-DA fluorescent assay. Fluorescence intensity was strongly reduced in cells treated with the fractions and elevated in H2O2-treated and untreated MCF-7 cells. The effect of the fractions on metastasis was assessed by determining their effects on MCF-7 cell migration, attachment and invasiveness using wound healing assay, adhesion assay and Boyden chamber invasion assay, respectively. The wound healing assay showed the fractions to have strong inhibitory activities on the migration of MCF-7 cells. The xii ability of the cells to attach to cell culture treated plates was also greatly reduced in cells treated with the fractions. The n-butanol fraction was demonstrated to exhibit a time- and dose-dependent inhibition on MCF-7 cell invasion by reducing the cells’ capability to penetrate through the matrigel matrix to the bottom of the porous membrane. Gelatin-zymography was done to assess the effect of the n-butanol fraction on activity of MMP-2 and MMP-9. The fraction showed to completely inhibit the gelatinolytic activity of MMP-2 and no band corresponding to the molecular weight of MMP-9 was observed, suggesting that MCF-7 cells produce undetectable levels of MMP-9. The n-butanol fraction further showed to down-regulate the expression of a range of proteins such as MMP-9, uPA, VEGF, TGF-β1 implicated in metastasis and angiogenesis determined using the human angiogenesis antibody array kit. This study demonstrated that the fractions of R. communis extracts have the ability to inhibit major processes of the metastatic cascade by down-regulating the expression of proteins relevant to metastasis. Thus, the fractions can be considered as potential anti-metastatic agents functional in the regulation and/or treatment of malignant of cancers. / National Research Foundation (NRF)

Infectious diseases are the major cause of human death worldwide and the need for new generations of anti-infective agents to overcome the drug resistant urgently needs to be tackled. Plant natural products are potential sources of novel antimicrobial compounds. In this study, an investigation into the antimicrobial lead compounds from Michelia figo, Macleaya cordata and Ardisia gigantifolia in Lingnan region is presented. The prevention of dental diseases is targeted at the control of dental biofilm. Streptococcus mutans and S. sobrinus are the leading bacterial strains in the formation of dental biofilm. Extracts of Michellia figo and Macleaya cordata displayed antimicrobial potential in our screening assays. Bioassay-guided isolation of M. figo revealed the presence of artabotryside B and acteoside which were isolated for the first time from this plant. Moreover, chelerythrine and sanguinarine, the two alkaloids isolated from Macleaya cordata displayed the ability to prevent the formation of biofilms of S. mutans and S. sobrinus with the MIC50 values in the range of 18.5-34.0 μM. Anti-TB bioassay-guided isolation of the extract of Ardisia gigantifolia led to isolation of two 5-alkylresorcinols, 5-(8Z-heptadecenyl) resorcinol (1) and 5-(8Z-pentadecenyl) resorcinol (2). We further synthesized 15 derivatives based on these two compounds. Resorcinols 1 and 2 exhibited anti-TB activity with MIC values at 34.4 μM and 79.2 μM in MABA assay, respectively, and 91.7 μM and 168.3 μM in LORA assay, respectively. Among these derivatives, compound 8 was found to show improved anti-TB activity than its synthetic precursor (2) with MIC values at 42.0 μM in MABA assay and 100.2 μM in LORA assay. Chelerythrine and sanguinarine are the representative and the major active constituents of M. cordata. Both compounds showed significant fungicidal effects in vitro and significant therapeutic effects on guinea pigs of dermatophytosis. Mechanism study for the antifungal efficacy showed that chelerythrine and sanguinarine were potent inhibitors of ergosterol bio-synthesis by reducing the amount of ergosterol without affecting the synthesis of 1,3-β-glucan. In summary, these results highlight the promising antimicrobial activity of chelerythrine, sanguinarine and alkylresorcinols from the medicinal plants in Lingnan region. The active compounds may be regarded as new hits for further study as novel classes of antimicrobial agents for the treatment of infectious diseases.

South Africa has one of the richest and diverse floras in the world with over 30000 species of higher plants. There are approximately 3000 species of medicinal plants in South Africa. The discovery of active compounds in medicinal plants plays a strategic role in the phytochemical investigation of crude plant extracts. Secondary metabolites of medicinal plants are a major source of drugs for the treatment of various health disorders. Cardiac glycosides are one of the subgroups of steroids modified from terpenoids. The existence of cardiac glycosides in some plant species often indicates toxicity. Among the contagious elements, diseases caused by viruses are one of the major causes of death, disability, and social and economic disruption for millions of people. Viruses also cause many important plant diseases and are responsible for huge losses in crop production and quality in all parts of the world. According to literature, plants containing cardiac glycosides demonstrate potential for the discovery of more effective new drugs in the treatment of infection especially viral contagions. The main objectives of this study were to evaluate the antiviral (HSV-2 and PVYN), antibacterial and cytotoxic activities of South African plants containing cardiac glycosides. Furthermore, isolation and identification of compounds with an emphasis on cardiac glycosides was carried out. Eight plants known to contain cardiac glycoside compounds were selected. Leaves of Gomphocarpus fruticosus, Nerium oleander, Cotyledon orbiculata, the fruits and leaves of Strophanthus speciosus, the bulbs of Bowiea volubilis and Merwilla plumbea were selected to examine their antimicrobial activities, toxicity, antiviral and to isolate potential pure compounds. The ethanol extracts of all selected plants were screened for antibacterial activity against two Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and two Gram-negative (Escherichia coli and Klebsiella pneumonia) pathogens. Plant extracts showed promising antibacterial action against Gram-positive bacteria. The most active extract against both Gram-positive bacteria was C. orbiculata with the MIC value of 1.25 mg/ml. Cell toxicity was monitored by determining the effect of the ethanolic crude extracts on human embryonic kidney cell line (HEK 293) using the XTT method. All extracts exhibited high toxic effects with IC50 < 100 μg/ml on the tested cell line. The XTT assay was used to determine of the antiviral activity of crude ethanolic extracts on the kidney epithelial cells of African Green Monkey (Vero). The results revealed that the crude ethanolic extracts of all iv selected plants exhibited a cytotoxic effect on Vero cells at concentrations lower than their EC50. Consequently, the determination of antiviral activity of the selected plant extracts was not successful. Based on the chromatographic and bioassay results from the six plants selected for this study, the fruit extract of S. speciosus, belonging to the Apocynaceae family, was chosen for the isolation of compounds, particularly cardiac glycosides. All plant extracts were tested for antibacterial activity against E. coli (Gram-negative) and E. faecalis (Gram-positive) by using bioautography. The general TLC test showed more variety of compounds in the fruit extract of S. speciosus. The results of the bioassay showed promising activity of the fruit extract of S. speciosus and the bulb extract of B. volubilis against Gram-positive bacteria. The chromatographic investigation of the S. speciosus fruit extract led to the isolation of three pure compounds including a cardiac glycoside. The three compounds were identified based on NMR (1D and 2D) and HRMS. The isolated compounds were identified as: a triterpene (ursolic acid methyl ester), a sugar: myo-inositol methyl ester and an unidentified cardiac glycoside. According to literature, it is the first report of the isolation of ursolic acid methyl ester and myo-inositol-methyl ether from S. speciosus fruit extract. The isolated cardiac glycoside exhibited no inhibitory activity at 1.25 mg/ml (the highest concentration tested) against all four tested bacteria (S. aureus, E. faecalis, E. coli and K. pneumonia). The cytotoxicity and anti-HSV-2 screening of the isolated cardenolide demonstrated the highly toxic effect of this compound on the HEK 293 cell line with 4.62 μg/ml IC50 value and < 25 μg/ml IC50 of Vero cell line. No evidence could be found in the literature of the cytotoxic activity of cardiac glycoside compounds on the HEK 293 cell line. The ethanolic extracts of all plant extracts and isolated cardenolide were tested against the PVYN in vivo and in vitro. The results revealed that the high concentration (50 mg/ml) of M. plumbea, N. oleander, B. volubilis (fresh bulb), C. orbiculata and isolated cardenolide reduced the PVYN symptoms on tobacco plants in an in vivo experiment. In in vitro analysis, the high concentration (50 mg/ml) of S. speciosus (leaves & fruits), and especially M. plumbea (dry bulb) showed significant antiphytoviral activity. In vivo and in vitro results demonstrated that M. plumbea has potential antiphytoviral activity. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Plant Science / Unrestricted

>Magister Scientiae - MSc / Rooibos (Aspalathus linearis) is endemic to the Cederberg region of South Africa, and one of the few indigenous medicinal plants commercially cultivated in the country. International interest in rooibos is growing, and currently most of the rooibos harvest is exported overseas to more than 30 countries. Various problems hamper the growth of the rooibos industry, including insect pests, diseases, drought and a decreasing lifespan of the plants. The availability of whole-genome data for rooibos can contribute to the selection of genetically superior plants, facilitating not only the identification of important genes and metabolic pathways in rooibos, but also the establishment of breeding programs.

<p>U ovoj studiji su predstavljeni rezultati taksonomskog, fitogeografskog i ekolo&scaron;kog istraživanja urbane flore Novog Sada sa posebnim osvrtom na uče&scaron;će alohtonih vrsta, i&scaron;čezlih i ugroženih taksona i prirodne resurse lekovitog bilja. Sprovedene taksonomske analize su komparativno rađene na ukupnoj urbanoj flori (850) i flori ruderalnih stani&scaron;ta (344) Novog Sada. Zabeleženi su i&scaron;čezli i ugroženi biljni taksoni na teritoriji grada Novog Sada. Ukupno 79 vrsta se smatra da je nestalo sa područja grada Novog Sada do<br />dana&scaron;njeg period,a &scaron;to je 8,04% od ukupnog broja vrsta. Utvrđeno je&nbsp; 115 (12,85%) vrsta koje su ugrožene na području grada Novog Sada. Od ukupno 895 vrsta ruderalne flore invazivne vrste&nbsp; su zastupljene sa 74 predstavnika (8,25%). Analizom ukupne flore evidentirano je 123 lekovitih biljaka. Iz ukupne flore izdvojene su biljke sa etarskim uljem, alkaloidima, fenolima i vitaminima koje koristi zvanična medicina. Od ukupnog broja taksona, izdvojeno je 23 medonosne biljke, 25 krmnih biljaka, 60 ukrasnih vrsta, 35 industrijskih, 68 alergijskih biljaka i 7 vrsta koje vezuju tlo. Analizom odabranih biljnih organa invazivnih vrsta&nbsp; (<em>Solidago gigantea, Iva xanthifolia, Amorpha futicosa, Fallopia<br />japonica i Ailanthus altissima</em>)&nbsp; utvrđen je ukupni sadržaj fenola i flavonoida.<br />Najveći sadržaj analiziranih ukupnih sekundarnih biomolekula (fenola i flavonoida) je utvrđen u&nbsp;<em> Fallopia japonica, Ailanthus altissima&nbsp; i&nbsp; Amorpha fruticosa</em>.&nbsp; Antiradikalsko delovanje&nbsp; ispitivanih ekstrakata je utvrđeno na nivou neutralizacije reaktivnih kiseoničnih vrsta (OH, NO i DPPH radikala). Antiradikalsko delovanje na nivou neutralizacije&nbsp; OH radikala odnosno najsnažnije &bdquo;skevindžer&ldquo; delovanje ispoljeno je od strane ekstrakta lista <em>Fallopia japonica</em>&nbsp; (IC50=10,89 &mu;g/ml)&nbsp; dok je ne&scaron;to manju aktivnost pokazala&nbsp;cvast pomenute vrste (IC50=14,87 &mu;g/ml).</p> / null / <p>Results of taxonomy, phitogeogrphical and ecological analysis of ruderal flora of Novi Sad with special attention in alien species and medicinal plant as natural resorces of&nbsp; ruderal flora are presented in this Thesis. Floristic review involving, taxonomy,&nbsp; phitogeographical and ecological analysis of total (895) and ruderal flora (344) of Novi Sad. Extincted (79) and endangered (115) species were recorded in the urban flora of Novi Sad. Invasive species (74) were recorded in total flora (8,25 %).<br />Analysis&nbsp; of the total urban flora of Novi Sad as potential natural resorces recorded 123 medicinal herbs (32 alien and 91 native), 23 nectar and polen rich plants, 25 forage crops, 60 ornamental, 35 plants for industrial use, 68 allergic i 7 soil errosion control plants.<br />The analysis of sampled plant organs of invasive species (Solidago gigantea, Iva xanthifolia, Amorpha futicosa, Fallopia japonica i Ailanthus altissima) were determined total phenolic compounds and flavonoids. Antioxidant activity of plant extracts&nbsp; was determined at the level of neutralizing reactive oxygenspecies (OH,&nbsp; NO and DPPH radicals). The Content of total phenolics and flavonoids were determinated in&nbsp; Fallopia japonica, Ailanthus altissima&nbsp; and Amorpha fruticosa. The best values of OH radical&nbsp; neutralization indicated leaves of&nbsp; Fallopia japonica&nbsp; (IC50=10,89 &mu;g/ml) and flowers (IC50=14,87 &mu;g/ml).</p>

To determine whether the three Siegesbeckia plants can all serve as the origins of HS, we compared their fingerprint chromatograms and inhibitory effects on inflammatory mediators. Chemical analyses showed that the three species have different profiles, although they have common peaks in their fingerprint chromatograms. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) of the common peaks demonstrated that all samples of the three species tend to be species-dependently grouped and separated. Ten components contributing to the species discrimination were identified, of which 8 are long-chain fatty acids/esters, and 2 are darutoside and hythiemoside A. Inhibitory effects of the three species on NO production and IL-6 secretion in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages are different, with SG being the most and SP the least potent. These chemical and bioactivity assays support the notion that the three Siegesbeckia species cannot be equally used as the plant origins of HS.;This work provides a chemical and pharmacological basis for determining whether the three Siegesbeckia genus herbs SP, SO and SG can all serve as the origins of HS; and also provides pharmacological justifications for the clinical application of HS in treating inflammatory disorders.

Inflammasomes are cytosolic protein platforms whose assembly/activation, in order to resolve various types of threats, can be triggered by a multitude of microbial and host derived stimuli. Their discovery was the key breakthrough in the understanding of inflammation initiation. Although beneficial in clearing microbes and restoring physiological or tissue homeostasis, aberrant or excessive stimulation of inflammasomes leads to various pathologies. The activation of NLRP3 inflammasome is associated with the physio-pathogenesis or the potentiation of the severity of so many diseases including respiratory diseases, such as asthma, COPD, COVID-19, malaria, diabetes, atherosclerosis, etc. Considering the extent of the NLRP3 inflammasome in diseases, therapies targeting the inhibition of its activation appear as a promising approach for the management of a wide range of diseases. The objective of this research work was to investigate the potential of Rwandan medicinal plants in the inhibition of the NLRP3 inflammasome. To this end, we first carried out a field survey to collect ethnobotanical information on plants used for the treatment of asthma in Rwanda. The present thesis is divided into two main parts:- The ethnobotanical study and screening of Rwandan medicinal plants with inhibitory activity on NLRP3 inflammasome activation;- The isolation and structure characterization of the active ingredients responsible for NLRP3 inflammasome inhibition, and the investigation of antiplasmodial activity of selected plants.In the first part, 19 herbal recipes were reconstituted from 61 medicinal plants based on an ethnobotanical survey. Most of these recipes exhibited significant inhibition of the NLRP3 inflammasome activation. The four recipe extracts named R03Cn and R07Kn aqueous extracts, and R10MK and R19Sz organic extracts significantly downregulated the activation of caspase-1 (more than 70% at 50 µg/ml). As R19Sz revealed the best NLRP3 inflammasome inhibitory activity and was less toxic it was hence selected for further investigations. In the second part of the work, two unstudied plants from the R19Sz recipe were submitted to a bio-guided fractionation. This led to the isolation and identification of compounds including caffeic acid, isoquercetin, kaemferol-3-O-galactoside as being the major constituents responsible for the inhibition of NLRP3 inflammasome activation in H. noldeae, and to the isolation and identification of 7-O-glucopyranosyl-isoprunetin, isoprunetin, and luteolin as the main compounds responsible for the inhibitory activity of NLRP3 inflammasome activation in E. montanum. Additionally, in vitro anti-plasmodial activities coupled to cytotoxicity assays of some bio-guided fractionation of E. montanum led to the isolation and determined antiplasmodial activity of Eucomic acid (IC50 = 0.057µg/ml), 7-O-glucopyranosyl-isoprunetin (IC50 = 0.113 µg/ml), isoprunetin (IC50 = 0.042 µg/ml), Isoluteolin (IC50: 0.121 µg/ml) as the main compounds responsible for the antiplasmodial activity with the high selectivity indexes of 6 577, 2646.7; 5264.3 and 2005.8, respectively .Overall, the present work has potentiated the role of Rwandan herbal medicines in the treatment of asthma and malaria while paving ways at the molecular and functional levels allowing to say that these plants likely act on inflammation by inhibiting the NLRP3 inflammasome activation. / Option Biologie moléculaire du Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Doctor Educationis / The fungus Botrytis cinerea is an opportunistic pathogen on a wide variety of crops, causing a disease known as grey mould through infections via wounds or dead plant parts. Synthetic fungicides for controlling this disease are fast becoming ineffective due to the development of resistance. This, coupled with consumers' world wide becoming increasingly conscious of potential environmental and health problems associated with the build-up of toxic chemicals, (particularly in food products), have resulted in pressure to reduce the use of chemical pesticide volumes as well as its residues. An emerging alternative to random chemical synthesis is the study and exploitation of naturally occurring products with fungicidal properties. One group of compounds known as strobilurins produced by Strobilurus species, woodland basidiomycete fungi, is a good example of this phenomenon. Plants produce an enormous array of secondary metabolites, and it is commonly reasoned that a significant part of this chemical diversity serves to protect plants against plant pathogens. A problem with plant-produced compounds as potential fungicides is that in the natural state, they are generally only weakly active compared to synthetic fungicides. There have been reports on the uses of mixtures of synthetic fungicides for the control of plant pathogenic fungi. When utilized in two-way mixtures, such fungicides may maintain or enhance the level of control of a pathogen at reduced rates for both components utilized in combinations, or alone at normal rates. These studies provide an important precedent for the idea of synergism. For this study, we hypothesize that the addition of plant extracts may enhance the antifungal efficacy of the synthetic strobilurin fungicide, kresoxim-rnethyl against B. cinerea. We selected South African medicinal plant species such as Artemesia afra, Elyptropappus rhinocerotis, Galenia africana, Hypoxis hemerocallidea, Siphonochilus aetheopicus, Sutherlundia frutescence, Tulbaghia violacea and Tulbaghia alliaceae for this study. For the in vitro study, indigenous medicinal plant extracts were prepared at twofold dilution concentrations and combined with kresoxim-rnethyl at concentrations of 0.25 and 0.5% (w/v). The B. cinerea mycelial plug assays showed potent antifungal inhibitory effects with the plant extract and kresoxim-rnethyl mixtures. Further analyses of the mixtures indicate synergistic effects between the fungicide and plant extracts. I surmise that these in vitro effects are also achievable in vivo. Combinations of these agents represent an attractive avenue for the development of new management strategies for controlling B. cinerea in the future. A second study was conducted to analyse the final dose rates for synergistic reactions for combinations of kresoxim-methyl and medicinal plant extracts against B. cinerea in vivo. A series of two-fold concentrations of medicinal plant extracts were combined with kresoxim-methyl to conduct decay inhibition studies on Granny Smith apples. Synergistic effects were observed for many of the kresoxim-methyl and plant extract combinations. I, therefore, came to the conclusion that indigenous South African plant species produce modulators that potentiate the activity of fungicides. Whether these synergistic effects are due to the inhibition of fungal multi-drug resistant pumps require further studies at the molecular level. However, these inhibitory effects are likely to be advantageous for developing fungicide formulations and application strategies with low toxicity effects on the environment. This approach not only makes it possible to reduce fungicide concentrations while maintaining adequate decay control, but also ensures a reduction of the chemical residue on the fruit.

Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2021 / Tuberculosis is one of the top 10 leading causes of death in the world. The development of drug resistant strains of Mycobacterium tuberculosis such as Multidrug resistant (MDR) and Extensively drug resistant (XDR) strains further complicate the TB control. Medicinal plants present a possible source for new potential antitubercular drugs. They have played an important role in drug discovery, with many pharmaceutical products originating from them. Isolation and characterisation of new antitubercular compounds from plant extracts is relevant today because of the development of resistant strains. The aim of the study was to evaluate the antimycobacterial activity of the leave extracts of Croton gratissimus and Leonotis leonorus. The first step was to extract fine powder leaves of the two plant species using four (dichloromethane, acetone, hexane and ethanol/water) different solvent systems. Isolation of the fractions was done using column chromatography and preparative thin layer chromatography. Minimum inhibitory concentrations were determined using the broth dilution method and the values were recorded in μg/mL. All the isolated fractions from both plant species were evaluated for preliminary in-vitro antimycobacterial activity. Some of the isolated fractions showed an increased activity against the pathogen as compared to the crude extracts. All the crude extracts of the two plants had activity with MIC90 values greater than 125 μg/mL. Seven fractions obtained from Croton gratissimus showed potential activity against the pathogen with MIC90 values ranging from 30.61 to 64.88 μg/mL. Leonotis leonurus had three fractions with promising activity with MICs ranging from 1.963 to 62.51 μg/mL. The crude extracts of the two plant species showed that the two plant species have antioxidant properties. The qualitative antioxidant assay showed that DCM crude extracts had more antioxidants than all other extracts because of more clear zones against the purple background colour on the TLC plates. These was confirmed by the qualitative antioxidant assay where DCM crude extracts was able to inhibit the highest percentage of DPPH at different concentrations than all other solvent extracts. The DCM crude extracts of L. leonurus and Croton gratissimus inhibited 87 and 93 % of DPPH respectively at 250 μg/mL. The structures of the compounds within the isolated fractions were elucidated using NMR and confirmed by MS and FTIR spectroscopies. The NMR data showed that the isolated fractions were not pure compounds but mixtures of closely related compounds. The compounds whose structures were elucidated included two labdane diterpenoids (Croton A and Croton B) and a Cembranolide ((5E,10E,13R)-4-isopropyl-7,11-dimethyl-15-oxo-14-oxa-bicyclo [11.2.1] hexadeca-5,10-dien-7-yl acetate) from Croton gratissimus and a phenol (4-(3,3,4,4-tetramethylheptyl) benzene-1,2-diol)) from Leonotis leonurus. / National Research Foundation (NRF) and Sasol Foundation