Abstract
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.