Anti-platelet aggregation activity of melaleuca bracteata var.revolution gold derived betulinic acid and its derivatives

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dc.contributor.advisorOpoku, A.R.
dc.contributor.authorOluwagbemiga, Osunsanmi Foluso
dc.date.accessioned2016-07-11T07:06:41Z
dc.date.available2016-07-11T07:06:41Z
dc.date.issued2015
dc.descriptionA dissertation submitted to the Faculty of Science and Agriculture in fulfilment of the requirements for the degree of Doctor of Science in the Department of Biochemistry and Microbiology at the University of Zululand, South Africa, 2015en_US
dc.description.abstractAbnormal Platelet aggregations are implicated in the onset of cardiovascular diseases which are the leading cause of death and disability globally. Management of pathological platelet aggregation with medicinal plants is a promising approach in treatment of cardiovascular diseases. In this study, betulic acid (BA) and a mixture of betulinic acid and oleanolic acid (BA/OA) isolated from Melaleuca bracteata leaf extract and their acetyl derivatives (3-β acetylbetulinic acid) (BAA), (3-β acetylbetulinic acid and 3-β acetyloleanolic acid mixture) (BAA/OAA) were investigated for their antiplatelet aggregation, anti-inflammatory, anticoagulant, anti-oxidant and cytotoxicity activity. The compound structures were confirmed through spectral nuclear magnetic resonance (NMR), mass (MS) and infrared (IR) spectroscopy data analysis. The antiplatelet aggregation activities of the compounds were evaluated against four agonists (thrombin, collagen, adenosine diphosphate and epinephrine) used separately to induce platelet aggregation. The ability of the compounds to separately inhibit the hydrolysis of chromogenic substrate was used for antithrombin activity of the triterpenoids. The release of ATP and calcium mobilization from the cytosol, as platelets aggregate, was investigated using a commercial kit and Fura 2/AM respectively. The anti-acetylcholinesterase activity of the triterpenes was also investigated using a commercial kit. The compounds were fed to rats and the tail bleeding time was used to determine the ex vivo anticoagulation activity of the triterpenoids. The anti-inflammatory activity of the triterpenes was investigated using the cotton pellet-induced granuloma model in rats. The homogenates from the granuloma tissues were used to determine the effect of the test compounds on catalase (CAT) and superoxide dismutase (SOD) activities. The in vitro effect of the triterpenes on cyclooxygenase COX-1 and COX-2 activity was investigated. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay was used to investigate the cytotoxic effect of the triterpenoids against carcinoma (HEPG2) and human embryonic (HEK293) cell lines. All the test compounds exhibited significant anti-platelet aggregation activity, albeit to different degrees of efficacy. BAA showed the highest antiplatelet aggregation activity regardless of the agonists. Coupled with its anti-platelet aggregation activity, BAA also exhibited significant anti-inflammatory, antithrombin, acetylcholinesterase inhibition, phosphodiesterase inhibition, calcium mobilization inhibition, inhibition of the release of ATP from dense granules, anticoagulant, cyclooxgensase (COX-2) activity inhibition, and iron chelating activities. BAA also significiantly stimulates SOD and CAT activity. In addition to the efficacy, the weak cytotoxicity of triterpenoids indicated their safety as an antiplatelet agent. It was concluded that BAA could be served as a template for the synthesis of safer anti-platelet agent.en_US
dc.identifier.urihttps://hdl.handle.net/10530/1468
dc.publisherUniversity of Zululanden_US
dc.subjectmelaleuca bracteata --cardiovascular diseases --betulinic acid --oleanolic acid --en_US
dc.titleAnti-platelet aggregation activity of melaleuca bracteata var.revolution gold derived betulinic acid and its derivativesen_US
dc.typeThesisen_US
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