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A phytochemical investigation of two South African plants with the screening of extractives for biological activity.

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Two South African medicinal plants, Strophanthus speciosus and Eucomis montana, were investigated phytochemically. From Strophanthus speciosus a cardenolide, neritaloside, was isolated, whilst Eucomis montana yielded three homoisoflavanones, 3,9- dihydroeucomin, 4'-demethyl-3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9- dihydroeucomin. The structures were elucidated on the basis of spectroscopic data. The homoisoflavanones were screened for anti-inflammatory activity using a chemiluminescent luminol assay, modified for microplate usage. All of the homoisoflavanones exhibited good inhibition of chemiluminescence, with IC50 values for 3,9-dihydroeucomin, 4'-demethyl-3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9- dihydroeucomin being 14mg/mL, 7mg/mL, and 13mg/mL respectively. The IC50 value of 4'-demethyl-3,9-dihydroeucomin compared favourably with the NSAID control (meloxicam), which had an IC50 of 6mg/mL. Neritaloside was not screened for biological activity as the yield of 14.4mg was insufficient for the muscle-relaxant screen for which it was intended. An assay for antioxidant/free radical scavenging activity was also performed. All the compounds had excellent antioxidant/free radical scavenging activity, with percentage inhibition of the reaction being 92%, 96%, and 94% for 3,9-dihydroeucomin, 4'-demethyl- 3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9-dihydroeucomin respectively at a concentration of 10mg/mL. However, the control compounds, diclofenac and meloxicam, also exhibited strong activity, with the result that the precise mode of anti-inflammatory activity could not be unequivocally determined. The results from the biological screenings thus provided a rational scientific basis for the indigenous ethnomedicinal use of Eucomis species in the treatment of rheumatism, inflammation and pain.


Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.


Traditional medicine., Pharmacology., Anti-inflammatory agents., Plants--Medicinal--South Africa., Theses--Chemistry.