Antiplatelet and antithrombotic activity of ethanol extract of Embelia ribes

Abstract

Embelia ribes Burm (Myrsinaceae) is a large shrub found in hilly parts of India. In Ayurveda, it is used as an an- thelmintic and antifertility agent. Pharmacologically it proved to have cardioprotective effect, decreases the hy- perhomoncysteine levels and the factors indirectly related to thrombosis but no direct study on thrombosis has been done yet. The objective of the study was to find the effect of ethanol extract of Embelia ribes fruits on in vitro as well as in vivo models of thrombosis and the mechanism responsible for its activity. Ethanol extract of Em- belia ribes (EER) was evaluated for its antiplatelet activity in in vitro models such as ADP (3 µM) and thrombin (0.1 U/ml) induced platelet aggregation and inhibition of malondialdehyde (MDA) production (0.1, 0.25, 0.5 and 1 mg/ml). Acute oral toxicity study of EER was performed in rats according to OECD 423. Antithrombotic activity of EER (200, 400 and 600 mg/kg, 7 days p.o.) was determined in various thrombosis models such as A-V shunt in- duced thrombosis and stasis induced venous thrombosis in rats.EER was studied for its effect on coagulation cas- cade through its effect on activated partial thrombopastin time and prothrombin time (600 mg/kg for 7 days p.o.). Thrombolytic activity of EER was studied by its clot dissolving activity on stainless steel filament helix at the con- centration of 0.05, 0.1, 0.5 and 2.5 mg/ml. EER at the dose of 1 mg/ml showed upto 58% inhibition on ADP in- duced platelet aggregation and 29.5% inhibition on thrombin induced platelet aggregation and was found to sig- nificantly reduce MDA production in platelets i.e. 92% reduction at the dose of 1 mg/ml. EER did not produce mor- tality, changes in behavior or any other physiological activities in rats, for any of the selected doses. EER was eval- uated in animal models such as arteriovenous shunt induced and stasis induced thrombosis in rats where it showed significant reduction in weight of thrombus in both models, (i.e. 39% inhibition in A-V shunt induced thrombosis and 36% in stasis induced venous thrombosis model at the dose of 600 mg/kg) indicating its an- tithrombotic potential. The other possible mechanisms of action of EER were evaluated by studying its effect on coagulation cascade and its thrombolytic potential. EER neither has any effect on coagulation cascade nor does it have thrombolytic activity. The results of various in vitro and in vivo models studied indicate that E. ribes has a good potential as an antithrombotic agent and the possible mode of action could be due to its antiplatelet activity supported with an antioxidant action.