INHIBITORY ACTIVITY OF TRITERPENOIDS, EUGENOL AND EUGENOL ACETATE IN THROMBIN, ADENOSINE DIPHOSPHATE AND EPINEPHRINE-INDUCED PLATELET AGGREGATION

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Date
2012-11
Authors
HABILA, AMAYA JOBIN
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Abstract
Platelet hyper-aggregation is the underlying cause of cardiovascular diseases. The clinical limitation and adverse side effect associated with currently used anti-platelet aggregation agents have fuelled the search for more effective agents of natural origin. Oleanolic acid, maslinic acid and eugenol from Syzigium aromaticum and betulinic acid from Melaleuca bracteata were isolated. The isolated compounds were modified to their acetates to mimic the functionality of aspirin. The isolated and modified compounds were characterized using nuclear magnetic resonance (NMR) spectroscopic techniques to ascertain the structure of the compounds. The isolated and modified compounds were evaluated for platelet aggregation inhibition induced by Thrombin, Adenosine diphosphate (ADP) or epinephrine. The result of the platelet aggregation inhibition using thrombin, ADP and epinephrine as agonist on the test compounds showed that the highest inhibition exhibited by betulinic acetate on the thrombin-induced platelet aggregation (54.5±0.01 at 1mg/ml, 63.5±0.17 at 3mg/ml and 73.5±0.15 at 10mg/ml, IC50 0.81mg/ml) which was similar (P<0.05) to the values of Aspirin (65.4±0.07 at 1mg/ml, 72.1±0.03 at 3mg/ml and 76.5±1.22 at 10mg/ml, IC50 0.33mg/ml) and Heparin (65.9±0.59 at 1mg/ml, 66.9±0.03 at 3mg/ml and 70.6±0.16 at 10mg/ml, IC50 0.26) used as standards. Antioxidant activity was investigated using 1,1′-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS+ )) assay to suggest a mechanism of action of the test compounds. The anti-oxidant activities of the compounds showed that eugenol possessed significant (P<0.05) free radical scavenging activity with highest activity in the ABTS+ assay (57.7±0.002, at 0.0625mg/100ml, 75.3±0.003, at 0.125mg/100ml, 89±0.002, at 0.25mg/100ml, 89.7±0.001, at 0.5mg/100ml, 90.7±0.001, at 1mg/100ml and an IC50 0.05mg/100ml) which is more than those of the standards Ascobic acid (9.7±0.001, at 0.0625mg/100ml, 19.5±0.003, at 0.125mg/100ml, 26.0±0.001, at 0.25mg/100ml, 47.7±0.001, at 0.5mg/100ml, 60.9±0.002, at 1mg/100ml and an IC50 0.66mg/100ml) and Butylated hydroxyanisole (9.7±0.005, at 0.0625mg/100ml, 15.4±0.001, at 0.125mg/100ml, 21.9±0.002, at 0.25mg/100ml, 52.0±0.001, at 0.5mg/100ml, 65.8±0.001, at 1mg/100ml and an IC50 0.48mg/100ml)) used. The study suggests that the isolated and modified compounds be used as antiplatelet aggregation agents in the management of blood-clotting related diseases.
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A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, IN PARTIAL FULFILMENT FOR THE AWARD OF MASTER OF SCIENCE (M.Sc) IN BIOCHEMISTRY,
Keywords
INHIBITORY, ACTIVITY, TRITERPENOIDS,, EUGENOL, ACETATE, THROMBIN,, ADENOSINE, DIPHOSPHATE, EPINEPHRINE-INDUCED, PLATELET, AGGREGATION
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