BACKGROUND: This study evaluated in vitro antigiardial activity in four Indonesian plants (Archidendron fagifolium, Diospyros sumatrana, Piper betle and Shorea sumatrana) extracted in methanol, methanol-tetrahydrofuran, and water. These plants exhibiting promising anti-parasitic activity were selected on the basis of collected behavioral data and their ability to decrease parasite load in Sumatran orangutans. Extracts of Arabidopsis thaliana, a plant routinely used as a laboratory model in research, were used as a negative control. METHODS: Plant extracts of different concentrations (400, 100, 25 and 6.25 μg/ml) and metronidazole (100 μg/ml), a standard giardicidal drug, were incubated with 25,000 trophozoites per milliliter of growth medium in 12-well tissue culture plates under anaerobic conditions for 72 h. Cultures were counted in a hemocytometer using a light microscope and then statistically evaluated. The cytotoxicity of the extracts was determined by the MTT Cell Viability Assay. RESULTS: We recorded a statistically-significant decrease in giardia trophozoites in two extracts: the methanolic extract of A. fagifolium (Kruskal-Wallis: p = 0.013) and the aqueous extract of P. betle (Kruskal-Wallis: p = 0.002). Effective concentrations of 400 μg/ml and 100 μg/ml, respectively, were revealed. Cytotoxicity was not demonstrated. CONCLUSIONS: The results of our study show that extracts of A. fagifolium and P. betle have potential as an alternative treatment of G. intestinalis infection. This is the first scientific proof of the biological activity of A. fagifolium, confirming the assumption that orangutans use this plant (as well as P. betle) for self-medication.

Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 Brno 611 37 Czech Republic

Department of Chemical Biology and Genetics and Laboratory of Growth Regulators Faculty of Science Palacký University and Institute of Experimental Botany The Czech Academy of Sciences Šlechtitelů 27 Olomouc 77900 Czech Republic

Department of Parasitology Faculty of Veterinary Medicine Gadjah Mada University Yogyakarta Indonesia

Faculty of Agriculture and Technology South Bohemia University České Budějovice Czech Republic

Institute of Parasitology Biology Centre of the Czech Academy of Sciences v v i Branišovská 31 České Budějovice 37005 Czech Republic

Laboratory of Growth Regulators Faculty of Science Palacký University and Institute of Experimental Botany The Czech Academy of Sciences Olomouc Czech Republic Šlechtitelů 27 77900

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