[en] Matadine, a new alkaloid, has been isolated from the root bark of Strychnos gossweileri. Elucidation of its structure is mainly based on 1H and 1D NMR studies. Its cytotoxic activity has been tested on cancer cells and normal cells. Matadine is an anhydronium base as serpentine, that exerts also a selective inhibiting activity on B16 melanoma cells while it is less toxic in human 2002 non-cancer cells. This selective activity might be well due , as it seems to be the case for serpentine and alstonine, to a higher affinity of matadine for destabilized single-stranded DNA as mainly present in cancer cells.