Evaluation of the Phytotoxicity of Roots by Bioassays and Microscopic Analysis. Characterization of New Compounds.

Herbicides are a key element in agriculture but they do cause environmental problems and natural alternatives are being sought. In this context, invasive plants could provide an as yet unexplored source for the development of future herbicides. has great invasive potential in Brazilian environments as it hampers the establishment of other plants. The phytotoxicity of root extracts has been evaluated, and the major components have been identified. The phytotoxicity of the extract was assessed in the wheat coleoptile assay on seeds of troublesome weeds and on , a tree species used in ecological restoration programs. The ethyl acetate extract showed the highest activity, and the most affected weeds were , , and with the latter weed more affected by the extract than by the herbicide Logran. Microscopic ultrastructural analysis of roots indicated possible signals of cell death. Seven compounds were identified in the ethyl acetate extract of which one diterpene and four saponins are new. Six of these compounds were tested in the wheat coleoptile bioassay. The most active were diterpene and saponins , , and . The phytotoxic activity of explains the issues observed in ecological restoration with in the presence of species, and its effect on weeds reinforces its potential use in agriculture.