Concerned about weed infestation, a major threat to food
production
and herbicide resistance that interferes in the mechanism of action
of the main herbicides, we have synthesized eight isatin derivatives
using the “Click Chemistry” approach through copper-catalyzed
azide–alkyne cycloadditions (CuAAC). Sixteen isatin derivatives
were evaluated for their phytotoxic activity against the seed culture
of the model plants, Lactuca sativa and Allium cepa. Six of them showed
phytotoxic activity similar to the positive control, trifluralin.
Hypocotyl length measurement analysis in L. sativa revealed that triazole derivative 8 is more active
than trifluralin. For A. cepa, root
length measurement analyses revealed that 3, 10, 14, 16, and 17 were similar
to the positive control trifluralin. Three-dimensional quantitative
structure–activity relationship (3D-QSAR) comparative molecular
field analysis (CoMFA) model construction using the acetolactate synthase
(ALS) crystallographic structure displayed pk
i values of predicted inhibitory activity and contour maps
revealing sterically bulky groups for 11, the CF3 group in ortho, and for 17, Br in ortho, favoring
the inhibitory ALS activity.