ASSESMENT OF PLATELET ANTIAGGREGANT ACTIVITY OF A FRACTION FROM AN ETHANOLIC EXTRACT OF THE BARK OF Nectandra amazonum Nees

This study shows the antiplatelet effect of the ethanolic fraction obtained from the bark of Nectandra amazonum Nees. [N.V. “laurel amarillo”, Lauraceae] applying the Born turbidimetric method. The screening test compared the fraction of N. amazonum (0.1 mg/mL), acetylsalicylic acid (ASA 0.5 mM, as reference standard) and the DMSO (0.1%, as control) in human platelets stimulated with adenosine diphosphate (ADP 2 µM), epinephrine (EPI 2 µM), collagen (COL 1 µg/mL) and arachidonic acid (AA 0.2 mg/mL). Subsequently, the study focused to determine the antiaggregant potency of the fraction throw concentration - response curves (from 1 µg/mL to 0.4 mg/mL), obtaining the pIC50 (-log IC50) values against these platelet agonists. The results showed that whereas the control platelets attained higher percentage values of aggregation (96% AA, 89% EPI, 85% COLL, 77% ADP). N. amazonum fraction significantly reduced these effects (6% AA, 45% EPI, 10% COLL, 21% ADP), near to that obtained with ASA (17% AA, 21% EPI, 10% COLL, 20% ADP). According to concentration - response curves, the pIC50 values of the fraction gave the following order of potency: AA, 4.90 > ADP, 4.51 > COLL, 4.33 > EPI, 3.85. These results suggest that N. amazonum Nees. ethanolic fraction elicit antiplatelet effects specially related to the inhibition of arachidonic acid pathway.