Natural products as allelochemicals. 11. Sesquiterpene lactones with potential use as natural herbicide models (I): trans,trans-germacranolides

A structure-activity study to evaluate the effect of the trans,trans-germac ranolide sesquiterpene lactones costunolide, parthenolide, and their 1,10-e poxy and 11,13-dihydro derivatives (in a range of 100-0.001 mu M) on the gr owth and germination of several mono and dicotyledon target species is acco mplished. Results are compared with those obtained in the same bioassay wit h an internal standard, the commercial herbicide Logran, to validate the re sults with a known active formulation and to compare the results with a com mercial product to test their potential use as natural herbicide models. Th ese compounds appear to have a more selective effects on the radicle growth of monocotyledons. Certain factors such as the presence of nucleophile-acc eptor groups and their accessibility enhance the inhibitory activity. The l evels of radicle inhibition obtained with some compounds on wheat are total ly comparable to those of Logran and allow to propose them as lead compound s.