Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

M.Sc. / To successfully intervene in the HIV/AIDS pandemic, knowledge of the pathogenesis of the disease and factors that stimulate or inhibit viral replication are crucial. Plants are expected to produce antiviral compounds since viruses form one of the major groups of plant pathogens. The objective in this project was to investigate the effects of 6 plant extracts on immune responses as well as evaluate their potential anti-HIV activity. Plant species tested were: Hypoxis hemerocal/idea, Elephantorrhiza elephantina, Spirulina platensis, Echinacea purpurea, Echinacea pal/ida and Cannabis sativa. Extracts were prepared via 24 hour extraction or 12 hour reflux in H20, methanol and ethanol in a 1:5 ratio. The crude extracts were analysed by TLC and HPLC and shown to consist of complex related mixtures of compounds. Using LC-MS, partial identification of methanol extracts revealed the following expected compounds: 9- octadecenoic acid (E)- in Hypoxis hemerocallidea, 4H-1-benzopyran-4-one,2-(3,4- dihydroxyphenyl)-7 -(13-D-glucopyranosyloxy)-5-hydroxy- in E/ephantorrhiza e/ephantina, ethanol,2-butoxy-,phosphate in Spirulina platensis, 2-propenoic acid,3-(3,4-dihydroxyphenyl)- in Echinacea purpurea, 2-propenoic acid,3-(3,4-dihydroxyphenyl)- in Echinacea pal/ida and ~-9- tetrahydrocannabivarin in Cannabis sativa tincture. Viability assays using tetrazolium salts (XTT) gave a qualitative picture of events allowing us to assess host cell responses and extract toxicity. Extracts exhibited intrinsic absorbances at some visible wavelengths but did not interfere at the wavelengths used in this viability assay. Having analysed cell viability it was thought prudent to report on the type of cell death induced by either HIV or the extracts, so Annexin-V (indicator of apoptosis) and PI (indicator of necrosis) detected by flow cytometry was employed. Results obtained revealed that cells were driven towards necrosis rather than apoptosis. None of the extracts showed significant in vitro toxicity in CEMss, CEMNKR. U937, Jurkat and PM1 cells or ex vivo in PBMC at a concentration range of 1000f..lg/ml-4f.!g/ml. Viability assays were also an indirect indication of HIV's effect on the cells. As for the effect of extracts on the immune system, IL-2 secretion was stimulated by most of the extracts. The effect of plant extracts on HIV activity was also investigated by looking at core protein levels (p24 was generally decreased by methanol extracts), reverse transcriptase activity (no detectable influence) and envelope glycoprotein levels (gp120 levels were only marginally reduced). It appears that Echinacea purpurea, Echinacea pal/ida and Spirulina platensis have immune enhancing abilities, while Hypoxis hemerocallidea, Elephantorrhiza e/ephantina and Cannabis sativa have dual purposes by enhancing both immunity and inhibiting HIV activity.

The acquired immunodeficiency syndrome (AIDS) in humans, which is caused by the human immunodeficiency virus type 1 (HIV-1) remains among the leading causes of death worldwide. Although HAART has reduced HIV mortality significantly, adhering to the recommended drug schemes, significant toxicities experienced by treated patients, and the high mutation rate of the virus that seem to easily circumvent the action of these drugs emphasize the need for alternative treatment strategies. Medicinal plants are a good source for the discovery of novel antimicrobial chemotherapeutic agents. Reverse transcription is the most essential step for viral replication to succeed successfully. This makes reverse transcriptase the prime target for antiviral therapy against HIV. Emphasis was placed on the discovery of plants with inhibitory activity against HIV-1 reverse transcriptase. Crude extracts from the active plant(s) was screened in vitro for their ability to suppress HIV replication in suitable cell systems. The potential of isolating and identifying the active principle(s) was also investigated. Crude extracts from different parts of Gunnera perpensa showed similar amounts of inhibition: aqueous extracts (97% „b 0.110%SD), methanol/chloroform extracts (94% „b 2.374%SD), rhizome extracts (96% „b 0.475%SD), stem extracts (94% „b 3.723%SD), leaf extracts (96% „b 1.097% SD). Crude extracts were found to be significantly (P„T0.027) non-toxic to CEM.NKR.CCR5 cells and PBMCs at 5 ƒÝg/ml. In acutely infected CEM.NKR.CCR5 cells, acutely infected PBMCs, and chronically infected PBMCs Gunnera perpensa extracts did not significantly (P>0.05) increase cell viability or reduced HIV core protein content, over 4 days. The in vitro test did therefore not reflect the findings with the reverse transcriptase assay. Activity-guided fractionations of Gunnera perpensa rhizome extract lead to the collection of a significantly active fraction. NMR studies revealed the presence of an epimeric mixture of glucose ¡§contaminants¡¨ in this active fraction. The presence of these ¡§contaminants¡¨ concealed the true structure of the active principle. Gunnera perpensa was identified as containing a potential active principle that significantly inhibits recombinant HIV reverse transcriptase. Unfortunately, in vitro experiments could not confirm this finding. The identity and structure of the active principle remains unidentified. Future studies will be concerned with in vitro antiviral studies of the pure active principle. Furthermore, preliminary tests indicated that some of the original collection of crude extracts had anti-bacterial and anti-malarial activities. These findings can be investigated in future. / Dr. D. Meyer

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