The Piper genus is distributed in both hemispheres in tropical and subtropical regions ( Jaramillo and Manos, 2001). It has been the subject of studies that have noted its insecticidal, fungicidal, and PLX4032 molecular weight trypanocidal actions ( Miranda et al., 2002, Scott et al., 2008 and Freire-de-Lima et al., 2008). The toxicity of Piper aduncum to the cattle tick Rhipicephalus (Boophilus) microplus has also been reported ( Silva et al., 2009). Native of northeastern Brazil, L. sidoides (Verbenaceae) is

popularly known as “alecrim-pimenta”, “estrepa-cavalo” and “alecrim-bravo”. Scientific studies have revealed its effects against some bacteria ( Aguiar et al., 1984 and Bara and Vanetti, 1998), Leishmania ( Oliveira et al., 2009a) and Aedes aegypti larvae ( Carvalho et al., 2003). In turn, M. piperita (Lamiaceae), which comes from the Mediterranean region and is known as peppermint, is cultivated as a hybrid of Mentha aquatica L. and Mentha spicata L. across the world. It exhibits antiseptic, antibacterial, fungicidal, antispasmodic and stimulant

actions ( Mimica-Dukić et al., 2003 and McKay and Blumberg, 2006). H. crepitans (Euphorbiaceae) is naturally distributed throughout Central and South Y-27632 chemical structure America, from Costa Rica to the Amazon. In Brazil, it is popularly known as “assacu” or “açaçu” ( Brondani, 2006). Its seeds and sap were formerly used as a purgative and also as a popular medicine to treat elephantiasis, leprosy, rheumatic fever, swelling and intestinal parasites ( Francis, 1990). The latex has been observed to have an effect on larvae of the ticks R. (Boophilus) microplus and R. sanguineus ( Brondani, 2006). Finally,

C. guianensis (Meliaceae) is a tree that is generally found both in Central and in South America, popularly known as “andiroba”. The essential oil extracted from this plant is used industrially in the production of candles, shampoos, soaps and repellents ( Pastore Junior and Borges, 1998 and Pastore Junior and Borges, 1999). Some studies have reported various effects produced by this plant, such as anti-allergic isothipendyl and analgesic effects ( Penido et al., 2006a), acaricidal action ( Farias et al., 2009), anti-inflammatory effect ( Penido et al., 2006b) and insect repellent action ( Miot et al., 2004 and Mendonça et al., 2005). Furthermore, the tea prepared with C. guianensis’s bark and flowers is used both as an anthelmintic and healing agent in humans ( Boufleuer, 2004). Considering the advances made in this research in recent years, this study aimed to evaluate the in vitro antiparasitic action of five plants (P. tuberculatum, L. sidoides, M. piperita, H. crepitans and C. guianensis) against H. contortus, and the in vivo action against Strongyloides venezuelensis in rats. The extracts from the five plant species were produced in the laboratories of several institutions. The Institute of Chemistry of Paulista State University, São Paulo state, provided the crude extract prepared from 18 kg of leaves of P.