Evaluation of the Antiprotozoal Activity of Neo-clerodane Type Diterpenes from Salvia polystachya against Entamoeba histolytica and Giardia lamblia Fernando Calzada, 1 * Lilian Yepez-Mulia, 2 Amparo Tapia-Contreras, 2 Elihú Bautista, 3 Emma Maldonado 3 and Alfredo Ortega 3 1 Unidad de Investigación Médica en Farmacología de Productos Naturales, UMAE Hospital de Pediatría, 2º Piso CORCE, Centro Médico Nacional Siglo XXI, IMSS, Av. Cuauhtemoc 330, Col. Doctores, CP 06725, México D.F., México 2 Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, UMAE Hospital de Pediatría, 2º Piso, Centro Médico Nacional Siglo XXI, IMSS, Av. Cuauhtemoc 330, Col. Doctores, CP 06725, México D.F., México 3 Instituto de Química de la Universidad Nacional Autónoma de México, Circuito Exterior, Cd. Universitaria, Coyoacán CP 04510, México D.F., México Chia (Salvia polystachya Ort., Lamiaceae) is frequently used in Mexican traditional medicine to treat dysen- tery. In this study the main neo-clerodane diterpenes (polystachynes A, B and D, as well as linearolactone) were isolated from the aerial parts of chia, and their antiprotozoal activities toward Entamoeba histolytica and Giardia lamblia trophozoites were evaluated in vitro. Linearolactone was the most potent antiamoebic and antigiardial compound with IC 50 values of 22.9 mM for E. histolytica and 28.2 mM for G. lamblia. Polystachynes A, B and D, showed moderate antiprotozoal activity against both protozoans with IC 50 values ranging from 117.0 to 160.6 mM for E. histolytica and from 107.5 to 134.7 mM for G. lamblia. These data suggest that linearo- lactone may play an important role in the antidiarrhoeal activity of S. polystachya. Copyright © 2009 John Wiley & Sons, Ltd. Keywords: Salvia polystachya; neo-clerodane diterpenes; linearolactone; antiprotozoal activity; Entamoeba histolytica; Giardia lamblia. INTRODUCTION Morbidity and mortality due to enteric protozoan infec- tions are a serious health problem in the world, particu- larly in developing countries where there are poor sanitary conditions. Symptomatic patients usually present diarrhoea or dysentery together with a wide range of abdominal symptoms such as stomachache, cramps, bloating or tenderness (Otshudi et al., 2000; Amstrong and Cohen, 1999; Taylor et al., 1995). The two main causes of such symptoms are Entamoeba his- tolytica and Giardia lamblia, the protozoa that cause amoebic dysentery and giardiosis, respectively (Upcroft and Upcroft, 2001; Casburn-Jones and Farthing, 2004). Metronidazole is the drug now most widely used in the treatment anaerobic protozoan parasitic infections caused by the flagellate G. lamblia and the amoeba E. histolytica. It is effective; however, potential carcino- genic, teratogenic, embryogenic effects and clinical and laboratory-generated drug-resistant strains of both pro- tozoa have been reported. Moreover, in prolonged treatment or high doses patients experience dry mouth, metallic taste, headache, vertigo, nausea, and in some cases, neurotoxic side effects (Müller et al., 2006). In an effort to improve the therapy for giardiasis and dysen- tery, new drugs that retain therapeutic efficacy and are devoid of adverse effects, should be discovered. Medici- nal plants used to treat gastrointestinal disorders could be a source of such new drugs. Salvia polystachya Ort. (Lamiaceae), popularly known as ‘chia’ is used in Mexican traditional medicine as a purgative, antigastralgic, antipyretic, and to treat dysentery. Previous phytochemical work done with the aerial parts of S. polystachya led to isolation of nine neo-clerodane diterpenes: salvifaricin, linearolactone, dehydrokerlin and polystachynes A–F (Maldonado and Ortega, 2000; Ortega et al., 2006). To our knowledge, there are no reports in the literature on the antiamoebic and antigiardial activities of S. polystachya and its con- stituents. Thus, the present work was undertaken to evaluate a possible antiprotozoal activity of the crude extract and four neo-clerodane diterpenoids (Fig. 1) from S. polystachya using an in vitro antiprotozoal assay. MATERIAL AND METHODS General experimental procedures. IR spectra were recorded as KBr pellets on a Perkin-Elmer 599 B spec- trophotometer. 1 H-NMR (300 MHz) and 13 C-NMR * Correspondence to: Dr. Fernando Calzada Bermejo, Unidad de Inves- tigación Médica en Farmacología de Productos Naturales, UMAE Hospi- tal de Pediatría, 2º Piso CORCE, Centro Médico Nacional Siglo XXI, IMSS, Av. Cuauhtemoc 330, Col. Doctores, CP 06725, México D.F., México E-mail: fercalber1@hotmail.com Received 08 December 2008 Revised 03 May 2009 Copyright © 2009 John Wiley & Sons, Ltd. Accepted 20 May 2009 PHYTOTHERAPY RESEARCH Phytother. Res. 24: 662–665 (2010) Published online 16 July 2009 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/ptr.2938