A phytochemical investigation of two South African plants with the screening of extractives for biological activity.
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Date
2006
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Abstract
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.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.
Keywords
Traditional medicine., Pharmacology., Anti-inflammatory agents., Plants--Medicinal--South Africa., Theses--Chemistry.