Synthesis and herbicidal potential of substituted aurones

Background: With the objective of exploring the herbicidal activity of substituted aurones, a series of 4,6-disubstituted and 4,5,6-trisubstituted aurones were synthesised, and their herbicidal activities against Brassica campestris L. and Echinochloa crusgalli (L.) Beauv. were evaluated in laboratory bioassays. Effects of some of the compounds were evaluated on seed germination. The most active compounds in the laboratory were evaluated in the greenhouse.

Results: The compounds were characterised by (1)H NMR, (13)C NMR and HRMS; some of them were further identified by IR. A (Z)-configuration was assigned to the aurones, based on spectroscopic and crystallographic data. Bioassay results of root growth showed that the aurones had a moderate herbicidal activity against the dicotyledonous plant Brassica campestris. (Z)-2-Phenylmethylene-4,6-dimethoxy-3(2H)-benzofuranone(6o) was the most active compound, with 81.3 and 88.5% inhibition at 10 and 100 µg ml(-1) respectively, equal to the activity of mesotrione. Some of the aurones possessed some inhibition of germination on several plant species. For glasshouse tests, the substituted aurones had lower herbicidal activity than metolachlor and mesotrione.

Conclusion: It is possible that aurone derivatives, which possess structures different from those of the commercial herbicides, may become novel lead compounds for the development of herbicides against dicotyledonous weeds with further structure modification.