Journal of Medicinal Plants Research Vol. 5(16), pp. 3781-3790, 18 August, 2011 Available online at http://www.academicjournals.org/JMPR ISSN 1996-0875 ©2011 Academic Journals Full Length Research Paper In vitro anti-Leishmania amazonensis activity of the polymeric procyanidin-rich aqueous extract from Syagrus coronata Igor A. Rodrigues 1,2 *, Daniela S Alviano 1 , Marta T. Gomes 1 , Davi O. Silva 3 , Rosemar Antoniassi 4 , Antonio Jorge R. Silva 5 , Humberto R. Bizzo 3 , Celuta S. Alviano 1 , Alane B. Vermelho 1 and Maria do Socorro S. Rosa 1 1 Departamento de Microbiologia Geral, Instituto de Microbiologia Prof. Paulo de Góes (IMPPG), Centro de Ciências da Saúde (CCS), Universidade Federal do Rio de Janeiro (UFRJ), Bloco I, Ilha do Fundão, 21941-590, Rio de Janeiro, RJ, Brazil. 2 Programa de Pós Graduação PNPD CAPES/FAPERJ, Instituto de Microbiologia Prof. Paulo de Góes, Centro de Ciências da Saúde (CCS), Bloco I, Universidade Federal do Rio de Janeiro (UFRJ), Ilha do Fundão, 21941-590, Rio de Janeiro, RJ, Brazil. 3 Programa de Pós-graduação em Biotecnologia Vegetal, Decania, Universidade Federal do Rio de Janeiro, RJ, Brazil. 4 Embrapa Agroindústria de Alimentos, RJ, Brazil. 5 Núcleo de Pesquisas de Produtos Naturais (NPPN), Universidade Federal do Rio de Janeiro, RJ, Brazil. Accepted 23 May, 2011 Leishmania amazonensis is one of the major etiological agents of diffuse cutaneous leishmaniasis, which is frequently unresponsive to all known treatments. Syagrus coronata (Arecaceae) is a palm tree with industrial applications used in local medicine by the Brazilian “caatinga” communities. This work evaluates the in vitro leishmanicidal activity of S. coronata on L. amazonensis. Promastigote forms of L. amazonensis were treated with different concentrations of the aqueous extract from S. coronata. In addition, we evaluated the effect of the aqueous extract on infection of mouse peritoneal macrophages and nitric oxide production. The minimal inhibitory concentration (MIC) of the aqueous extract of S. coronata was 8.3 μg/ml. Morphological changes in L. amazonensis promastigotes treated with 50 μg/ml of the aqueous extract were observed by light microscopy. Pretreatment of mouse peritoneal macrophages with 33 μg/ml of S. coronata aqueous extract reduced the association index between macrophages and L. amazonensis by 70.4%, with a concomitant increase of 158.3% in nitric oxide production by the infected macrophages. In addition, the aqueous extract exhibited no cytotoxic effect on mammalian cells and elicited no allergic reactions in vivo, indicating good prospects for the development of new drugs of herbal origins to treat leishmaniasis. Key words: Antileishmanial activity, crude extracts, nitric oxide, polyphenols, semi-arid vegetation. INTRODUCTION Leishmaniasis is a tropical disease caused by species of the Leishmania genus that are spread throughout Africa, Asia, Europe, North America and South America, with an estimated 12 million people infected worldwide and a global incidence of 2 million new cases annually (CDC, 2011). Clinically, leishmaniasis occurs in visceral, *Corresponding author. E-mail: iar_rodrigues@yahoo.com.br. cutaneous and mucocutaneous forms, with 90% of the latter present in Afghanistan, Saudi Arabia, Algeria, Brazil, Iran, Iraq, Syria and Sudan (WHO, 2010). The New World form of the disease is mainly transmitted by flies of the genus Lutzomyia (Ashford, 2000). Upon inoculation of the host, promastigotes are phagocytized by skin macrophages, where they transform into ovoid bodies known as amastigotes. In mammals, Leishmania are dimorphic obligate intracellular parasites that infect and multiply primarily within the phagolysosomal