Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 1999
Publication Date: N/A
Interpretive Summary: This review describes natural product-based strategies for the discovery of herbicides. Successful examples of natural products derived herbicides include phosphinothricin, bialaphos, cinmethylin, and the triketone derivatives. We report that phytotoxic natural products act on a large number of unexploited herbicide target sites that may be useful to the pesticide industry.
Technical Abstract: Although natural product-based discovery strategies have not been as successful for herbicides as for other pesticides or pharmaceuticals, there have been some notable successes. Phosphinothricin, the biosynthetic version of glufosinate, and bialaphos are phytotoxic microbial products that have yielded commercial herbicides. Cinmethylin, a herbicidal analogue of cineole, has been sold in Europe and the Asia. The triketone herbicides are derivatives of the plant-produced phytotoxin leptospermone. These products represent only a small fraction of commercialized herbicides, but they have each introduced a novel molecular target site for herbicides. Analysis of the literature reveals that phytotoxic natural products act on a large number of unexploited herbicide target sites. The pesticide industrys natural product discovery efforts have so far concentrated on microbially-derived phytotoxins, primarily from non-pathogenic soil microbes, involving screening large numbers of exotic isolates. Plant pathogens usually produce potent phytotoxins, yet they have received relatively little attention. Even less effort has been made to discover plant-derived phytotoxins. Bioassay-redirected isolation has been the preferred method of discovery after a producing organism is selected. This laborious approach often leads to rediscovery of known compounds. Modern tandem separation/chemical characterization instrumentation can eliminate much of this problem by identification of compounds before they are bioassayed.