Evaluation of the anti-inflammatory potential of medicinal plants through an ethnopharmacological approach

Rachel Wei Li

This thesis is an account of a systematic investigation of medicinal plants with a history of traditional use in the treatment of inflammatory conditions. The ethnopharmacological investigation of 58 Australian and 41 Chinese plants was undertaken. Anti-inflammatory activity, cytotoxicity and phytochemistry of 13 Australian and 15 Chinese plants were studied. Through this systematic investigation, the traditional use of these plants for inflammatory conditions has been explored in a laboratory setting. Evidence for the effectiveness of a number of these plants has been demonstrated in vitro. A novel compound with anti-inflammatory activity and a favourable toxicological profile is identified. Medicinal plants have been used in all cultures for centuries and a wealth of information on their traditional use in the treatment of various diseases, including inflammation, has been documented or passed from one generation to the next. This valuable information about ethnobotany and ethnomedicine, its contribution to the development of ethnopharmacology and western medicine, and its utilisation for the current research and drug development of anti-inflammatory agents are reviewed in Chapter 1. Traditional Chinese herbal medicine and Australian indigenous medicine are also discussed. From this literature review, a series of hypotheses were generated to test the anti-inflammatory activity, safety and active ingredients of plants selected through an ethnopharmacological approach. The subsequent laboratory experiments were designed to test these hypotheses. Chapter 2 describes the model of a cross cultural dataset comparisons used in the plant selection for this study. General laboratory methods of in vitro enzyme assays, cytotoxicity study and phytochemical investigation are overviewed. The validation of the methods of enzyme assays and toxicological assays, and the statistical methods used are discussed. Chapter 3 describes the screening of plant extracts prepared from the 28 plant species for their inhibition of cyclooxygenase-1. Eight plant extracts exhibiting 70-100% inhibition of cyclooxygenase-1 were further investigated for their inhibitory activities on cyclooxygenase- 2, phospholipase A2 and 5-lipoxygenase. Chapter 4 describes the cytotoxicity of eight plant extracts selected in Chapter 3. The cytotoxicity of these extracts was evaluated using an adenosine triphosphate (ATP)-based luminescence assay on three cell lines. The cell lines were human skin fibroblast (1BR3), human Caucasian hepatocyte carcinoma (Hep G2) and human Caucasian promyelocytic leukaemia (HL-60). No major cytotoxicity was observed. Chapter 5 describes a bioactivity guided phytochemical investigation of three extracts of Tinospora smilacina Benth. (Menispermaceae), Ficus racemosa L. (Moraceae) and Clematis pickeringii A Gray. (Ranunculaceae). Three known compounds were isolated and identified as the major active compounds responsible for the anti-inflammatory activity of the plant extracts. A novel compound isolated from the inner bark of Ficus racemosa was elucidated using mass spectroscopy (MS) and nuclear magnetic resonance (NMR). This novel compound demonstrated a potent dual inhibitory activity on cyclooxygenase-1 and 5-lipoxygenase. Chapter 6 provides a discussion of the research strategy and the results of laboratory investigation in light of the hypotheses generated. The direction of future research is also discussed.

Evaluation of the anti-inflammatory potential of medicinal plants through an ethnopharmacological approach

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Evaluation of the anti-inflammatory potential of medicinal plants through an ethnopharmacological approach

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