Browsing by Author "Campbell, William E"

Now showing 1 - 13 of 13
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    Antimalarial activity and cytotoxicity of some South African medicinal plants and their active constituents
    (2008) Sekhoacha, Mamello; Smith, Peter J; Campbell, William E
    Includes bibliographical references (leaves 150-187).
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    The antimalarial activity of Dicoma anomala and the chloroquine resistance reversing effects of Sclerocarya birrea on Plasmodium falciparum in vitro
    (2001) Matsabisa, Motlalepula Gilbert; Folb, Peter I; Smith, Peter J; Campbell, William E
    Two plants, Dicoma anomala [Sond.]; a member of the Asteraceae and Sclerocarya birrea [(A. Rich) Hoechst. subspecies caffra (Sond.) Kokwaro], a member of the Anarcadiaceae families, are used widely in Africa for a variety of traditional treatments. In this thesis it has been shown that these plants possess in vitro pharmacological activities against the malaria parasite. The extracts of D. anomala are active in vitro against Plasmodium falciparum and those of S. birrea selectively enhance the in vitro accumulation of chloroquine in resistant strains of Plasmodium falciparum.
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    Antimycobacterial activity of the red algae gelidium pristoides, plocamium corallorhiza and polysiphonia virgata
    (2006) Saravanakumar, Denise; Folb, Peter I; Smith, Peter J; Campbell, William E
    In 1993, the World Health Organisation declared tuberculosis a global health emergency. Currently, efforts are underway to improve the way the disease is managed and to find more effective treatments that would combat the problem of long treatment periods, toxicity, drug-resistance and HIV-coinfection. In the process, natural product chemistry continues to play an important role in the search for new compounds to treat tuberculosis. Terrestrial plants have been investigated for antimycobacterial activity, while marine plants are yet to receive as much attention. In this project, three South African marine plants were drawn into the search for novel anti-tuberculosis compounds. One of the seaweeds is already part of the local seaweed industry, namely Gelidium pristoides, while Plocamium corallorhiza and Polysiphonia virgata have economic potential. These three red algae were extracted extensively and fractionated using preparative layer chromatography and preparative centrifugally accelerated radial thin-layer chromatography (Chromatotron). The crude extracts of the algae showed no inhibitory activity to growth of the causative agent of human tuberculosis, Mycobacterium tuberculosis. However, when the purified fractions were tested against M. tuberculosis in the BACTEC-460 radiometric method at a concentration of 125 μg/mL, fractions 322, 323 and 333 of P. virgata showed 100% inhibition, while two fractions of G. pristoides showed 91.7% and 79.2% inhibition, respectively. Two fractions of P. corallorhiza demonstrated 41.2% and 73.5% inhibition. The bioactive fractions of P. virgata were further purified and resulted in the isolation of a known compound namely, 2-methoxyethyl-2-methacrylate (MEMA). When MEMA was tested by radiometric assay against M. tuberculosis, it showed anti-tuberculosis activity at a MIC-value of 100 μg/mL and no cytotoxicity against Chinese hamster ovarian cells. However, in a re-investigation into the bioactive compounds of P. virgata it was established that MEMA was not the major bioactive compound. Long chain fatty acids were responsible for the antimycobacterial activity of the algal extract particularly oleic acid, linoleic acid, dodecanoic acid, and myristic acid. Oleic acid inhibited the growth of M. tuberculosis at and MIC-value of 25 11 g/rnL, while dodecanoic acid, myristic acid and linoleic acid all had MIC-values of 50 μg/mL. Stearic acid and palmitic acid was also isolated from the seaweed, but only moderate inhibition of M. tuberculosis was observed for at MIC-values of 50 μg/mL. Oleic acid showed moderate inhibition at 50 μg/mL against the multi-drug resistant isolate of M. tuberculosis, while myristic acid and dodecanoic acid showed significant inhibition against the same at 50 μg/mL and moderate inhibition at 25 μg/mL. Linoleic acid also inhibited the growth of the multi-drug resistant strain at 50 μg/mL. Oleic acid showed the most inhibition of the growth of M. smegmatis in direct bioautography with an MIC-value of 0.8 μg/mL, while linoleic acid and dodecanoic acid had MIC-values of 1.56 μg/mL and 3.125 μg/mL., respectively. Stearic acid, palmitic acid, and myristic acid did not inhibit the growth of M. smegmatis.
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    Chemical modification and pharmacological evaluation of the antimalarial natural product totarol
    (2004) Tacon, Claire; Smith, Peter J; Chibale, Kelly; Campbell, William E
    Includes bibliographical references.
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    Investigation of the phytochemistry and biological activity of isoquinoline alkaloids isolated from the South African medicinal plants, cyrtanthus sanguineus (Lindl.) walp. and cyrtanthus obliquus (L.f.)ait
    (2001) Brine, Natalie Dawn; Campbell, William E; Smith, Peter J; Folb, Peter I
    The term "traditional medicine" refers to the ways of protecting and restoring health that existed before the arrival of modern medicine. These approaches to health belong to the traditions of each country and have been handed down from generatio to generation.
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    Isolation and characterisation of antiplasmodial compounds from Xerophyta species and the bioavailability, metabolic and efficacy evaluation of 9-0-acetylhydnocarpin in a mouse model
    (2008) Wiesner, Lubbe; Smith, Peter J; Campbell, William E
    Includes abstract. Includes bibliographical references (leaves 237-265).
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    Isolation and characterisation of two antiplasmodial diterpenes from Harpagophytum procumbens (Devil's Claw) and chemical modification of a related analogue
    (2002) Clarkson, Cailean; Smith, Pete; Campbell, William E; Chibale, Kelly
    Bibliography: leaves 153-171.
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    Isolation and characterization of antiplasmodial compounds from Siphonochilus aethiopicus and Aloe ferox and bioavailability of a novel furanoterpenoid
    (2008) Lategan, Carmen; Smith, Peter J; Campbell, William E
    Includes abstract. Includes bibliographical references (leaves 138-162).
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    The isolation of anti-mycobacterial compounds from South African medicinal plants
    (2005) Madikane, Eliya Vukani; Smith, Peter J; Campbell, William E; Elisha, G B
    Includes bibliographical references.
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    The isolation, characterization and antiplasmodial activity of two novel dimeric sesquiterpenes from Dicoma anomala
    (2006) Tselanyane, Malefa Lydia; Folb, Peter I; Matsabisa, M G; Campbell, William E
    The study investigates the antimalarial potential of a Southern African traditional medicinal plant, Dicoma anomala (Sond.). The plant is used to treat a variety of treatments including fevers. The extracts of the leaves and twigs have been reported to treat malaria and fever but the treatments with the roots are unrelated to malaria.
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    Phytochemical studies on traditional medicinal plants with antimalarial activities
    (1997) Chen, Dianne Tzu-Hsiu; Gammon, David W; Campbell, William E
    The active antimalarial principles of three traditional medicinal plants, Passerina obtusifolia (Thymelaeaceae), Tetradenia riparia (Labiatea) and Xerophyta retinervis (V elloziaceae) were investigated by employing bioassay guided fractionation. Two novel compounds and five known constituents were isolated from the active fractions of these three plants. The types of compounds isolated included: three triterpenoids (20(29)-Lupene-3α,28- diol (30), 20(29)-Lupene-3α, 16β,28-triol (32) and 3β-Hydroxy-20(29)-Lupen-28-oic acid (42)); two diterpenoids (8-Abietene-7 β,13 β -diol (45) and cariocal (51)); one flavonoid ( 5-Hydroxy:.4' ,6, 7-trimethoxyflavone ( 44)) and one flavonolignan ( 11-0- acetyl hydnocarpin (62)). In addition, one analogue of 7α-hydroxyroyleanone (41) (which was previously isolated from T riparia and was found to be the active antimalarial principle of the plant) was prepared.
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    The pyrrolizidine alkaloids : studies on the pyrrolizidine base Retronecanol
    (1968) Welgemoed, Jacobus Cornelius; Campbell, William E
    Degradative and biosynthetic studies were performed on retronecanol1 obtained from monocrotaline, the alkaloid present in Crotalaria spectabilis. Previously two different theories regarding the biosynthesis of the pyrrolizidine bases had been proposed. Conflicting results in this school emphasised the need for a critical examination of the degradative procedure. Heliotridane, derived from retronecanol, was submitted to the Hofmann degradation. The product of the reaction was shown by gas-liquid chromatography to be a mixture with at least five components. Attempts to separate and purify the components were unsuccessful, although some information regarding their identity was deduced. The mass spectra of retronecanol, heliotridane and heliotridene were obtained and plausible rationalisations of these spectra are presented. In order to circumvent the difficulties previously encountered in the degradation, attempts were made to obtain retronecanone from retronecanol by oxidation on a small scale. Three different oxidants, however, failed to give the required product. Plants of Crotalaria spectabilis were fed with [5-¹⁴C]-ornithine, followed by degradation of the active monocrotaline 1 obtained to give the activities of carbon atoms 1 and 1' of the pyrrolizidine base. The results are consistent with a theory which invokes a symmetrical intermediate in the biogenesis of ring B of the pyrrolizidine unit.
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    The therapeutic effectiveness of some local Nigerian plants used in the treatment of malaria
    (2010) Melariri, Paula E; Smith, PJ; Campbell, William E
    In Nigeria most of the populace relies heavily on medicinal plants for the treatment of malaria. This thesis describes the investigation of the antiplasmodial properties of seven plants used in the traditional treatment of malaria in Nigeria. The seven plants include Mangifera indica L., Citrus limon L. Burm.f, Musa sapientum L., Psidium guajava L., Carica papaya L., Cymbopogon citratus Staph, and Vernonia amygdalina Delile. These plants are widely distributed in Nigeria and are used in Nigerian folk medicine to treat malaria and febrile illnesses. It is apparent that experimental evaluation of herbal drugs for the treatment of malaria is rather impressive, however, only few are in the market and very few have reached clinical trials. Researchers need to take more active interest in the investigation and standardization of herbal drugs with potent antimalarial activity.