Thirty extracts of plants traditionally used by the Chacobos, a native community living in the Amazonian part of Bolivia, were screened in vitro and/or in vivo for antimalarial activity. Two of the four species designated as antimalarial, Geissospermum laeve and Maquira coriacea, displayed rather good activity, corroborating their traditional uses. However, they did show a rather high toxicity in vivo. Among twelve species used to cure symptoms relevant to malaria, five showed good activity: Apuleia leiocarpa, Bauhinia guianensis, Nectandra cuspidata, Sparattanthelium amazonum, Tanaecium jaroba. Two species, Qualea paraensis and Sclerolobium aff. guianense, used to treat scabies, showed interesting antimalarial activity in vivo; three other species (Iryanthera laevis, Prunus amplifolia, Pterocarpus aff. amazonum) used for various medicinal purposes, apparently not related with a Plasmodium infection, also showed antimalarial activity. Finally, one species (Derris amazonica) used as a piscicide displayed good in vitro activity, in the same way as one Annonaceae, Guatteria aff. schomburgkiana, used for construction purposes.

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The present study examines the effects of the extracts [petroleum ether, CHCl3, CHCl3/MeOH (9:1) and MeOH], partially purified fractions and pure compounds from Guettarda acreana on the electrically induced contractions (E.C.I.) of the isolated guinea-pig ileum. The results of the experiments indicate that CHCl3/MeOH (9:1), MeOH extract, and the MeOH soluble part from CHCl3/MeOH extract tested at concentrations of 1.2, 2.5, and 5 micrograms/ml, dose-dependently reduced the guinea-pig ileum contractions. Furthermore, some partially purified fractions I-IV from the MeOH extract, each tested at the same concentrations of the extracts, and some pure compounds (6 x 10(-6), 3 x 10(-6), 1 x 10(-6) M) isolated from the above fractions significantly reduced, in a dose-dependent manner, the electrical contractions of the ileum. The active compounds were identified as the known indole alkaloids strictosidic acid, lyalosidic acid, 5 alpha-carboxystrictosidine, strictosidine, and sickingine, as well as the known quinic acid derivatives 5-caffeoylquinic acid, 4,5-dicaffeoylquinic acid, and shikimic acid by spectral data. Two known quinovic acid glycosides and a new triterpenic glycoside, quinovic acid 3 beta-O-alpha-rhamnopyranosyl-(1-->3)-(beta-glucopyranosyl-(1-->6)-beta- glucopyranoside, were also isolated and their structures established by NMR and M5 data.

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