Pharmacological Research 55 (2007) 23–30 Antiplatelet and antithrombotic activities of essential oil from wild Ocotea quixos (Lam.) Kosterm. (Lauraceae) calices from Amazonian Ecuador Vigilio Ballabeni a , Massimiliano Tognolini a , Simona Bertoni a , Renato Bruni b , Alessandra Guerrini b , Gabriela Moreno Rueda c , Elisabetta Barocelli a,∗ a Dip. di Scienze Farmacologiche, Biologiche e Chimiche Applicate, Universit` a di Parma, Viale G.P.Usberti 27/A, 43100 Parma, Italy b Dip. di Biologia Evolutiva e Funzionale, Sez. Biologia Vegetale e Orto Botanico, Universit` a degli Studi di Parma, Viale G.P.Usberti 11/A, 43100 Parma, Italy c Fundacion Chankuap’, Soasty y Domingo Comin, Macas, Ecuador Accepted 25 September 2006 Abstract Ocotea quixos essential oil was shown to possess significant inhibitory activity of platelet aggregation and clot retraction in rodent plasma. This study is aimed at fully characterizing the antiplatelet activity of the whole essential oil and its main components trans-cinnamaldehyde and methyl cinnamate also in human plasma, at investigating the mechanism underlying such activity and at evaluating the potential antithrombotic activity of subacute treatment of mice with Ocotea essential oil. In vitro Ocotea essential oil and trans-cinnamaldehyde inhibited arachidonic acid-, U46619-, ADP-, phorbol12-myristate13-alcetate-, collagen-induced platelet aggregation and thrombin-induced clot retraction in human and rodent plasma; Ocotea oil and trans-cinnamaldehyde competitively antagonized contractions induced by thromboxane A 2 receptor agonist U46619 in rat isolated aortic ring (K B = 18 and 3.2 g ml -1 , respectively). In vivo Ocotea oil, orally administered in a subacute treatment (30–100 mg kg -1 day -1 for 5 days) to mice, prevented acute thrombosis induced by collagen-epinephrine intravenous injection. This antithrombotic activity was not accompanied by pro-haemorragic side effect, as detected by the inactivity in bleeding test, thus showing a favourable safety profile compared to the conventional antiplatelet agent, acetylsalicylic acid. Present findings indicate that Ocotea essential oil possesses potent and safe antithrombotic activity attributable to its antiplatelet and vasorelaxant effects. The main constituent trans-cinnamaldehyde seems to be the primary responsible for this activity through a putative mechanism involving the inhibition of thromboxane A 2 receptors. © 2006 Elsevier Ltd. All rights reserved. Keywords: Ocotea quixos; Antiplatelet activity; Experimental thrombosis; Bleeding; Thromboxane A 2 antagonism 1. Introduction The genus Ocotea includes more than 350 tropical and sub- tropical aromatic shrubs or trees distributed within the Americas and in Southern Africa. Most of them are important timber trees subjected to be felled off because of the deforestation process of the rainforest habitat. They constitute a large source of essential oils with a predominant phenylpropanoid pathway and some of them, i.e. those from O. pretiosa, O. sassafras, O. caudata and O. cymbarum, have a renewed market position mainly in the perfume industry [1]. Ocotea quixos (Lam.) Kosterm. (Lauraceae) (=Nectandra cinnamomoides Nees., = Laurus quixos Lam.) is a small tree ∗ Corresponding author. Tel.: +39 0521 905093; fax: +39 0521 905091. E-mail address: barocell@unipr.it (E. Barocelli). (5–20 m) with greenish floral buds, white flowers, dimorphic fruits and coriaceous leaves with reddish venations, bright glossy green on adaxial surface and yellowish on the abaxial. Once con- sidered endemic of the rainforests of Ecuador, it has recently been collected also in southern Colombia and Peru [2,3]. It has been traditionally esteemed for its aromatic properties since the Incaic times and appreciated as appetizer, eupeptic, dis- infectant and as local anaesthetic [4,5]. Its leaves are also used to make an anti-diarrheic infusion. Every two years the tree produces big, woody flower calices, locally called Ish- pink (Quechua, Shuar, Cofan), Ocatuhue viqui (Huaorani) or Flor de Canela. Due to their cinnamon-like smell, Ishpingo calices are traditionally used by indigenous people of the Ama- zon as a cinnamon-substitute spice and to aromatize sweets and cakes: the essential oil obtained from the floral calices is, in fact, mainly composed of odoriferous phenylpropanoids like trans-cinnamaldehyde and methyl cinnamate [6]. Recent 1043-6618/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.phrs.2006.09.009