Antiplatelet therapy constitutes a mainstay therapy for patients with acute coronary syndromes and generally high-risk patients with thrombosis. However, the occurrence of drug-resistance or tolerance observed in some patients for antithrombotic agentes limits the efficacy and applicability of the therapy. Hypericum perforatum (HP) or St John´s wort is presently one of the most consumed medicinal plants in world because of its biological activities. In contrast to the significant number of reports on the antidepressive effects of HP, little is known about its antiplatelet or anti-inflammatory actions. Thus, the effects of Hypericum perforatum on haemostasis and inflammation need to be elucidated in order to contribute to assess its therapeutic potential. Thus, the main objective of the project is to investigate the possible functional relevance of Hypericum perforatum on platelet reactivity. To achieve this aim, this work will be focus on two aspects: 1) Characterize the profile of platelet activation in the presence of HP extracts and 2) Study the interactions involving platelets and leukocytes, reactions underlying to inflammation.