Identification of bioactive compounds of a South African plant extract for combating potentially pathogenic oral microorganisms

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dc.contributor.advisor Lall, Namrita
dc.contributor.coadvisor Botha, Francien Susanna
dc.contributor.postgraduate Henley-Smith, Cynthia Joan
dc.date.accessioned 2013-09-09T12:06:48Z
dc.date.available 2012-08-14 en
dc.date.available 2013-09-09T12:06:48Z
dc.date.created 2012-04-19 en
dc.date.issued 2012-08-14 en
dc.date.submitted 2012-08-10 en
dc.description Dissertation (MSc)--University of Pretoria, 2012. en
dc.description.abstract Seven plants generally used for traditional oral care namely, Barleria albostellata, Cotyledon orbiculata, Dichrostachys cinerea, Heteropyxis natalensis, Carpobrotus edulis, Zanthoxylum capense and Dodonaea viscosa were investigated for antimicrobial activity and safety. Four pathogenic microorganisms, Actinomyces israelii, Streptococcus mutans, Prevotella intermedia and Candida albicans, were selected that represented the diversity of microbial flora in the oral cavity. No evidence could be found in the literature on the activity of the selected plant extracts against A. israelii, P. intermedia and S. mutans. Only H. natalensis exhibited activity against the Gram-positive microorganisms, A. israelii and S. mutans; minimum inhibitory concentration (MIC) was found to be 0.88 mg/ml and 1.82 mg/ml respectively. The MIC against the Gram-negative bacteria, P. intermedia was found to be 3.13 mg/ml. Dichrostachys cinerea exhibited activity towards a drug-sensitive stain of C. albicans (MIC of 10.71 mg/ml) and against a drug-resistant (polyene and azole resistant) strain of C. albicans (MIC of 10.42 mg/ml). Dichrostachys cinerea was the least toxic to both the Kidney epithelial cells of the African Green Monkey (Vero) and Human laryngeal epidermoid carcinoma cells (HEp-2) cell lines with 50% inhibitory concentrations (IC50) of 204 ± 0.13 μg/ml and 224 ± 0.1 μg/ml respectively. Heteropyxis natalensis was selected for further study as it exhibited moderate cytotoxicity (IC50 of 33.66 ± 0.04 μg/ml) on HEp-2 cells and the best antibacterial activity as compared to the other plant extracts investigated in this study. When H. natalensis was incorporated in a synergistic combination with the essential oils Melaleuca alternifolia (Tea tree) and Mentha piperita (peppermint); a fourfold reduction in the MIC of A. israelii was exhibited. Gingivitis, the infection of the gums, induces inflammation. To attract the white blood cell, leukocytes, to the site of infection; a chemokine known as Interluekin-8 (IL-8) is released. These cytokine, IL-8, levels were not reduced when the extract of H. natalensis was utilized to prevent the interaction of A. israelii with the epithelial cells, HEp-2. A Scanning Electron Microscopy (SEM) study to determine bacterial adhesion in the presence of H. natalensis indicated that the plant extract interferes with pellicle formation and glucan binding of S. mutans to the enamel surface of the tooth. Five known compounds were identified from the ethanolic extract of H. natalensis leaves and twigs. The compounds were identified as Aurentiacin A (1), Cardamomin (2), 5-hydroxy-7-methoxy-methylflavanone (3), Quercetin (4) and 3,5,7-trihydroxyflavan (5). The MICs of the compounds 1 and 4 were found to be 0.063 mg/ml and 1.0 mg/ml respectively against A. israelii. Compounds 2 and 5 exhibited no inhibitory activity at 1.0 mg/ml (the highest concentration tested) against A. israelii. This is the first report of the isolation of the five compounds and their activity against A. israelii. en
dc.description.availability Unrestricted en
dc.description.degree MSc
dc.description.department Plant Science en
dc.identifier.citation Henley-Smith, CJ 2012, Identification of bioactive compounds of a South African plant extract for combating potentially pathogenic oral microorganisms, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/31149> en
dc.identifier.other E12/4/510/gm en
dc.identifier.upetdurl http://upetd.up.ac.za/thesis/available/etd-08102012-150749/ en
dc.identifier.uri http://hdl.handle.net/2263/31149
dc.language.iso en
dc.publisher University of Pretoria
dc.rights © 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. E12/4/510/ en
dc.subject UCTD en
dc.title Identification of bioactive compounds of a South African plant extract for combating potentially pathogenic oral microorganisms en
dc.type Dissertation en


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