This work reports studies at the
molecular level of a series of
modified sulfonylureas to determine the chemophoric sites responsible
for their antifungal and herbicidal activities. For forage conservation,
high antifungal potency and low phytotoxicity are required. A molecular
modeling study based on multivariate image analysis applied to quantitative
structure–activity relationship (MIA-QSAR) was performed to
model these properties, as well as to guide the design of new agrochemical
candidates. As a result, the MIA-QSAR models were reliable, robust,
and predictive; for antifungal activity, the averages of the main
validation parameters were r
2 = 0.936, q
2 = 0.741, and r
2
pred = 0.720, and for herbicidal activity, the model was
very predictive (r
2
pred = 0.981
and r
2
m = 0.944). From the
interpretation of the MIA-plots, 46 novel sulfonylureas with likely
improved performance were proposed, from which 9 presented promising
calculated selectivity indexes. Docking studies were performed to
validate the QSAR predictions and to understand the interaction mode
of the proposed ligands with the acetohydroxyacid synthase enzyme.
Summary
Tylenchulus semipenetrans nematodes affect citrus crops and may develop resistance to commercially available nematicides. In this sense, two series of 1,3,4-oxa- and thiadiazole compounds have been recently synthesised and tested as nematicides against T. semipenetrans, demonstrating promising results. We report herein a molecular modelling study that combines these two series of congeneric compounds to form a single and enhanced data set. The chemical structures of these compounds were correlated with the respective nematicidal activities (pLC50) using multivariate image analysis (MIA) descriptors in quantitative structure-activity relationship (QSAR) analysis. The partial least squares (PLS) regression yielded reliable and predictive models (, , and ). Therefore, novel 1,3,4-oxa- and thiadiazole derivatives were proposed and a few of them exhibited predicted nematicidal performance better than those of the parent compounds.
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