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Research Centre for Plant Growth and Development

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Browsing Research Centre for Plant Growth and Development by Author "Jäger, Anna Katharina."

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    Evaluation of anthelmintic, antiamoebic and antibacterial activity in traditional South African medicinal plants.
    (2001) McGaw, Lyndy Joy.; Van Staden, Johannes.; Jäger, Anna Katharina.
    Traditional medicine in southern Africa draws upon a vast selection of plants to treat gastrointestinal disorders such as diarrhoea and intestinal parasites. The evaluation of these plants for biological activity is necessary, both to substantiate the use of these plants by healers, and also a possible lead for new drugs or herbal preparations. After a survey of the existing ethnobotanical literature, plants used to treat stomach ailments such as diarrhoea, dysentery or intestinal worm infestations were selected and submitted to bioassays according to their traditional uses. Extracts of the chosen plants were made using the solvents hexane, ethanol and water, to ensure the extraction of compounds with a wide range of polarity. In total, 138 extracts were tested for antibacterial activity, 72 for anthelmintic activity, and 42 for antiamoebic activity. Antibacterial activity was evaluated using the disc-diffusion assay, and Minimal Inhibitory Concentration (MIC) values were determined using a microdilution assay. The extracts were tested against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, and the Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae. Ethanolic extracts showed the greatest activity and Gram-positive bacteria were the most susceptible microorganisms. The free-living nematode Caenorhabditis elegans, which is morphologically similar to parasitic nematodes, was used in two different assays to evaluate anthelmintic activity. A microdilution technique was employed to investigate antiamoebic activity against the enteropathogenic Entamoeba histolytica, the causal organism of amoebic dysentery. These assays were suitable for the screening of a large number of extracts at one time. Several plants exhibited significant activity against these test organisms. Many species of plants belonging to the family Combretaceae are used in southern African traditional medicine against a variety of ailments, including abdominal complaints, bilharzia and diarrhoea. Extracts of powdered leaf material of 24 species belonging to the Combretaceae were prepared using the solvents ethyl acetate, acetone, methanol and water. These extracts were screened for anthelmintic activity. Significant activity was exhibited by C. apiculatum, C. hereroense and C. mossambicense. The most anthelmintic activity was shown by acetone extracts, followed by ethyl acetate, water and then methanol extracts. The aromatic rhizomes of Acarus calamus L. are used extensively in traditional medicine worldwide. They reportedly relieve stomach cramps and dysentery, and are used as anthelmintics. Rhizome extracts of A. calamus growing in KwaZulu-Natal, South Africa, exhibited anthelmintic and antibacterial activity in the initial general screening. Using bioassay-guided fractionation, the phenylpropanoid β-asarone was isolated from the rhizome. This compound possessed both anthelmintic and antibacterial activity. It has previously been isolated from A. calamus, and a related species, A. gramineus. Different varieties of A. calamus exhibit different levels of β-asarone, with the diploid variety containing none of the compound. Mammalian toxicity and carcinogenicity of asarones has been demonstrated by other researchers, supporting the discouragement of the medicinal use of Acarus calamus by traditional healers in South Africa. Schotia brachypetala was another plant to show good antibacterial activity in the initial screening. The roots and bark of S. brachypetala are used in South African traditional medicine as a remedy for dysentery and diarrhoea. The lack of pharmacological and chemical data on this plant prompted a further investigation into its antibacterial activity. The differences in activity of ethanol and water extracts with respect to plant part, season and geographical position were analysed. No extreme fluctuations in activity were noted. Two other Schotia species, S. afra and S. capitata, were included in the study, and both displayed good antibacterial activity. The storage of the plant, either as dried, ground plant material at room temperature, or as an extract residue at -15°C, had little effect on the antibacterial activity. Preparing the extracts from fresh or dry material also did not notably affect the activity. In general, the ethanolic extracts were more active than the aqueous extracts. The chemical profiles on TLC chromatograms were compared and found to be very similar in the case of ethanol extracts prepared in different months of the year, and from different trees. The extracts of the three species, and of the leaves stored under various conditions, as well as extracts prepared from fresh or dry material, also showed similar TLC fingerprints. However, various plant parts of S. brachypetala showed distinctly different chemical compositions. The leaves of S. brachypetala showed slightly higher antibacterial activity than the roots. Fractionation of the ethanol extract of the dried leaves using liquid-liquid partitioning and chromatographic techniques yielded 9,12,15-octadecatrienoic (linolenic) acid and methyl-5, 11,14,17-eicosatetraenoate. These fatty acids displayed antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, and activity to a lesser extent against the Gram-negative Escherichia coli and Klebsiella pneumoniae. Linolenic acid is known to have antibacterial activity. The screening of plants for biological activity yielded valuable preliminary information about the plants used by traditional healers to treat gastrointestinal illnesses. The isolation of biologically active compounds from two highly active plants was achieved.
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    Genetic transformation and micropropagation of Thapsia garganica L. - a medicinal plant.
    (2003) Makunga, Nokwanda P.; Van Staden, Johannes.; Jäger, Anna Katharina.
    No abstract available.
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    An investigation of the medicinal properties of Siphonochilus aethiopicus.
    (2002) Light, Marnie Elizabeth.; Van Staden, Johannes.; Jäger, Anna Katharina.
    Siphonochilus aethiopicus (Schweinf.) B.L. Burtt (Zingiberaceae), commonly known as wild ginger, is a highly sought after plant for use in traditional medicine in South Africa. Over-exploitation of this medicinal plant has resulted in regional extinction in the wild. As a result, there is great interest in the medicinal properties of S. aethiopicus, and as a plant for small scale cultivation to increase the supply for use in traditional medicine. Water, ethanol and ethyl acetate extracts were prepared from the leaves, rhizomes and roots of S. aethiopicus. These extracts were tested for in vitro anti-inflammatory activity in the cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) assays, and in the microdilution antibacterial assay. The aqueous extracts showed no significant prostaglandin synthesis inhibition in the COX-1 and COX-2 assays. The ethanol and ethyl acetate extracts of the leaves showed the highest levels of activity at a concentration of 250 µg ml¯¹ per test solution, in both the COX-1 and COX-2 assays. The ethanol and ethyl acetate extracts of the rhizomes and roots also had moderate levels of activity in the COX-1 assay. These results provide some evidence for the rational use of S. aethiopicus in traditional medicine for anti-inflammatory purposes. In the microdilution antibacterial assay, no inhibitory activity against the test bacteria was detected with the aqueous extracts. The ethanol and ethyl acetate extracts tested showed greater antibacterial activity at minimal inhibitory concentrations ranging from 0.78 to 3.13 mg ml¯¹ against the gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) than the Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae). No distinct differences were observed between the ethanol and ethyl acetate extracts, or between the different plant parts. A serial extraction of S. aethiopicus rhizome material was conducted and the extracts were tested in the COX-1 assay and the microdilution assay as a preliminary investigation for a bulk extraction. The hexane and ethyl acetate extracts gave slightly higher COX-1 inhibition than the ethanol extract. No distinct differences were observed in the microdilution assay. A bulk ethyl acetate extract of S. aethiopicus rhizome material was prepared, yielding 6.3 g of a thin orange oil. Vacuum liquid chromatography (VLC) was used to fractionate ≈4 g of the extract. The VLC fractions were evaluated using thin layer chromatography (TLC) and a bioautographic assay, using S. aureus as a test organism. The fractions were also tested in the COX-1 assay. The bioautography revealed a number of compounds which exhibited antibacterial activity. Fraction C was purified further using preparative TLC, and 24.9 mg of a pure compound from R,0.54 (toluene:ethyl acetate 93:7) was isolated. The structure of the compound was elucidated from nuclear magnetic resonance (NMR) spectra, and mass spectroscopy of the compound was also recorded. The compound was identified as the sesquiterpenoid furanoeremophil-2-en-1-one, which is structurally identical to the recently reported compound 4aαH-3,5α,8aβ-trimethyl-4,4a,9-tetrahydro-naphtho[2,3-b]-furan-8-one. The compound showed only a very minimal bacteriostatic effect in the microdilution assay. S. aethiopicus plants were harvested before and after seasonal senescence. Ethanol extracts were prepared from fresh or dried material of the leaves, rhizomes and roots, and tested in the COX-1 assay and the microdilution assay TLC fingerprints of the various extracts were also prepared. No noteworthy changes in COX-1 inhibition, due to senescence, were observed with extracts prepared from fresh material, although there did appear to be a slight decrease in activity in the α-roots and an increase in the β-roots after senescence (fresh and dry). A decrease in the antibacterial activity of the leaves and an increase in the antibacterial activity of the α-roots was observed after senescence. These results suggest that the time of harvest may only have a minimal influence on the degree of anti-inflammatory and antibacterial activity.