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The plants of Psychotria ipecacuanha (Brot.) Stokes (Rubiaceae) are perennial subshrubs (20 40 cm), the natural habitat of which is the understory in tropical hot humid forest of Central and South America. The roots of P. ipecacuanha are reddish-brown; consist of twisted fragments of around 15 cm long, no thicker than 6 mm and annulated (fig. 1.1.-A). The best known active principles in this plant are the isoquinoline alkaloids emetine and cephaeline (fig. 1.1.-B), localized principally in the cortex of the root and rhizome, but also many others alkaloids are isolated from different organs of this and related plant species (Bruneton, 1999). The so called ipecac alkaloids are used nowadays mainly in medicine as emetics (an agent that induces vomiting), expectorants and anti-amoebicides (Yoshimatsu & Shimomura, 1991). The use of this plant as a traditional herbal medicinal resource for several illnesses began somewhere with the native Brazilians. Commercial harvesting of this species began at the 16 th Century and European traders establish an export system to their home countries, where the drug was mostly used against dysentery (Evans, 1989; Oliveira and Martins, 2002). The protein-inhibiting effects of emetine or its somewhat safer form, dihydroemetine, and other ipecac alkaloids may account for the ability of the plant to inhibit growth or kill several types of microorganisms including parasites like amoeba (Wright and Phillipson, 1990; Schmeller and Wink, 1998). Other important compounds are psychotrine and O-methylpsychotrine that appear to be selective inhibitors of human immunodeficiency virus-1 reverse transcriptase (Tan et al., 1991).