Bioherbicidal activity of a germacranolide sesquiterpene dilactone from Ambrosia artemisiifolia L

Concerns about environmental involvement and insurgence of resistant weeds are moving the attention from synthetic herbicides to new solutions. In such context, allelopathic plants could provide natural molecules useful in weed management. Ambrosia artemisiifolia L. (common ragweed) is an invasive plant which allelopathic properties have been suggested by its field behaviour and demonstrated through phytotoxicity bioassays. However, the herbicide potential of the single molecules produced by the plant has not been explored. The phytotoxicity of crude extracts of A. artemisiifolia was confirmed by germination tests conducted on cress and radish. Semi-preparative fractionation of the methanol extract allowed separating a main inhibitory fraction which contained a single compound. The structure of the molecule was elucidated by LC-MS/MS, HRMS, NMR and FTIR as the sesquiterpene lactone isabelin (C15H16O4). The phytotoxicity of isabelin has been tested on four different weed species, confirming the inhibitory activity of the molecule. The results indicate directions for future studies about herbicidal specific activity of isabelin, as pure molecule or in the crude extract, as potential candidate for biological weed control.