Rodriguez,J.;Theoduloz,C. Laboratorio de Cultivo Celular, Facultad de Ciencias de la Salud, Universidad de Talca, Casilla 747, Talca, Chile Schmeda-Hirschmann, G. Natural Products Chemistry Laboratory, Institute of Chemistry of Natural Resources, University of Talca, Talca, Chile.The benzoquinone embelin and four alkyl phenols were isolated from an Argentinean collection of Oxalis erythrorhiza. 3-Heptadecyl-5-methoxy-phenol is reported for the first time. The structures were determined by spectroscopic methods. Embelin presented inhibitory effect on methicillin-resistant Staphylococcus aureus, Escherichia coli and the dermatophytic fungi Epidermophyton floccosum, Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes and Trichophyton rubrum with MICs ranging between 50 and 100 μg/ml. Furthermore, embelin was active against Trypanosoma cruzi trypomastigotes with 100% lysis at 100 μg/ml and cytotoxicity below the trypanocidal concentration. The new alkyl phenol 3-heptadecyl-5-methoxy-phenol was active towards Leishmania amazonensis and Leishmania donovani promastigotes with 100% lysis at 100 μg/ml. The cytotoxicity (IC50) of embelin and the new alkyl phenol on human lung fibroblasts were 739 and 366 μM, respectively. The plant is used to treat heart complains, a symptomatology related to Chagas’ disease which is endemic in the San Juan Province, Argentine.