[en] A study was conducted to characterize the anthelmintic activity and to isolate the main nematocidal agent of B. aegyptiaca plant. The anthelmintic activity was evaluated in vitro by means of an original anthelmintic assay using Caenorhabditis elegans as a biological model. Fluorescence microscopy was used for the determination of the percentage of worm death. The structure elucidation was based on NMR, mass spectroscopic analysis and chemical methods. A bioassay-directed fractionation of the aqueous extract of B. aegyptiaca led to the isolation of balanitin-7 (also named diosgenin 3beta-O-beta-D-xylopyranosyl-(1->3)-beta-D-glucopyranosyl-(1->4)-[alpha- L-rhamnopyranosyl-(1->2)]-beta-D-glucopyranoside), as being the principal nematicidal agent. These data indicate that balanitin-7 has an appreciable nematocidal activity, which is not mediated by inducing an anti-acetylcholinesterase activity.