In vitro anti-platelet aggregation activity of the extracts of protorhus longifolia
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Date
2011
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Abstract
Platelet aggregation beyond purpose of haemostasis is the underlying cause of
blood-clotting related diseases. Concoctions of P. longifolia are used by Zulu
traditional healers to manage such diseases. This work aimed at investigating the
anti-platelet aggregation activity of the extracts of this plant and to identify and
characterise the active components present and responsible for the anti-platelet
aggregation activity. Phytochemical screening of the plant material revealed the
presence of various secondary metabolites (tannins, flavonoids, alkaloids and
terpenoids). Crude extracts (obtained by sequential extraction of plant material with
hexane, chloroform, ethyl acetate, methanol and water) and two triterpenes (3-oxo-
5á-lanosta-8,24-dien-21-oic acid, and 3â-hydroxylanosta-9,24-dien-24-oic acid)
isolated and characterized (using various chromatographic and spectrometric
techniques-IR, MS, 1H-NMR, and 13C-NMR) from the crude chloroform extract were
screened for antioxidant, anti-platelet aggregation, anti-inflammatory activities, and
cytotoxicity. The antioxidant activity of the plant components was determined on
DPPH and ABTS+ radicals. Their reduction potential and chelating activity on Fe2+
were also determined. Except the methanol extract (IC50 of 0.07 and 0.16 mg/ml),
the crude extracts and the isolated compounds showed poor (< 50%) antioxidant
activities as they weakly scavenged DPPH and ABTS+ radicals, exhibited low
reduction potentials and poor Fe2+ chelating activities.
The anti-platelet aggregation activity of both the crude extracts and isolated
compounds was separately investigated on thrombin, ADP and epinephrine induced
rat platelet aggregation. The extracts and the isolated triterpenes exhibited a
concentration dependent anti-platelet aggregation activity induced by the three
agonists. The highest activity by the hexane extract (IC50 of 0.59 mg/ml) was
observed on the thrombin-induced platelet aggregation. In addition, the isolated
compound also exhibited in vitro anticoagulant activity on the whole rats blood.
The acute anti-inflammatory activity of the isolated triterpene was determined using
the carrageenan- induced rat paw oedema model. The compound (500 mg/kg body
weight) significantly (p<0.05) inhibited the acute inflammation of rat paw. The hexane
and chloroform extracts showed weak cytotoxic effects on brine shrimps with LC50
39.6 and 54.7mg/ml respectively. Also the pure compound- 3â-hydroxylanosta-9,24-dien-24-oic acid exhibited weak cytotoxic effects on HEK293 and HEPG2 cell lines
(IC50 8520 and 7960 ìg/ml respectively).
These results support the use of P. longifolia in folk medicine in the management of
blood-clotting related diseases.
Description
A dissertation submitted in fulfilment of the requirement for the Degree of
Masters of Science in the Department of Biochemistry and Microbiology,
Faculty of Science and Agriculture, University of Zululand, 2011.
Keywords
Platelet aggregation, Protorhus longifolia