The anti-platelet aggregation activity of Rapanea melanophloeos -A Zulu medicinal plant
Date
2011
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Abstract
Rapanea melanophloeos (L.) Mez is a medicinal plant that is used by Zulu traditional
healers to manage blood-clot related diseases.Various extracts (methanol, nhexane,
chloroform, ethyl acetate and water) prepared from the bark of R.
melanophloeos were screened for phytochemicals, antioxidant, and anti-platelet
aggregation activity.
Phytochemical screening of the plant showed the presence of tannins, terpenoids,
alkaloids, saponins, cardiac glycosides, flavonoids and phlobatannins. Steroids and
anthraquinone were however not detected. The extracts strongly (>70%) scavenged
1, 1 -diphenyl-2-picryhydrazyl and 2, 2-azinobis 3-ethyl-benzothiazoline-6-sulfonic
acid free radicals. The extracts had 91% chelating effect on Fe2+ ions and exhibited
concentration dependent reducing power.
The extracts showed varying degrees of inhibition (21% to 97%) of rat platelet
aggregation induced separately by thrombin, adenosine diphosphate (ADP) and
epinephrine. The extracts further exhibited antiplatelets aggregation activity on
enzymes (trypsin, papain and bromelain) treated platelets.
The lethality of the extracts was tested on brine shrimps larvae. Hexane and
chloroform extracts had LC50 values of 1068.731 mg/ml and 3648, 349mg/ml
respectively. A triterpene (3β-Hydroxylanosta-9, 24-dien-21-oic acid) wasisolated and
characterized (through various chromatographic techniques, extensive 1D and 2D
NMR spectroscopy) from the ethyl acetate extract.
The triterpene exhibited antiplatelet aggregation, and inhibition of
acetylcholinesterase activity. The cytotoxicity of the triterpene on two cell lines
(HEK293 and HEPG2) gave LC50 values of 851.5 μg/ ml and 796.0 μg/ ml
respectively.
The results suggested that the extracts of Rapanea melanophloeos could be
considered as herbal treatment for disease associated with blood clotting.
Description
Submitted to the Faculty of Science and Agriculture, in partial fulfilment of the requirements for the degree of Master of Science in the Department of Biochemistry and Microbioogy
at the University of Zululand, 2011.
Keywords
Rapanea melanophloeos (L.) Mez, Blood-clot related diseases, Phytochemical screening