Tembotrione, a 4-hydroxyphenylpyruvate dioxygenase (HPPD)
inhibitor,
has been widely used in many types of plants. Tembotrione has been
reported for its likelihood of causing injury and plant death to certain
corn hybrids. Safeners are co-applied with herbicides to protect certain
crops without compromising weed control efficacy. Alternatively, herbicide
safeners may effectively improve herbicide selectivity. To address
tembotrione-induced Zea mays injury,
a series of novel ester-substituted cyclohexenone derivatives were
designed using the fragment splicing method. In total, 35 title compounds
were synthesized via acylation reactions. All the compounds were characterized
using infrared spectroscopy, 1H and 13C nuclear
magnetic resonance spectroscopy, and high-resolution mass spectrometry.
The configuration of compound II-15 was confirmed using
single-crystal X-ray diffraction. The bioactivity assay proved that
tembotrione phytotoxicity to maize could be reduced by most title
compounds. In particular, compound II-14 exhibited the
highest activity against tembotrione. The molecular structure comparisons
as well as absorption, distribution, metabolism, excretion, and toxicity
predictions demonstrated that compound II-14 exhibited
pharmacokinetic properties similar to those of the commercial safener
isoxadifen-ethyl. The molecular docking model indicated that compound II-14 could prevent tembotrione from reaching or acting with Z. mays HPPD (PDB: 1SP8). Molecular dynamics simulations showed
that compound II-14 maintained satisfactory stability
with Z. mays HPPD. This research revealed
that ester-substituted cyclohexenone derivatives can be developed
as potential candidates for discovering novel herbicide safeners in
the future.
Nicosulfuron is the leading herbicide in the global sulfonylurea
(SU) herbicide market; it was jointly developed by DuPont and Ishihara.
Recently, the widespread use of nicosulfuron has led to increasingly
prominent agricultural production hazards, such as environmental harm
and influence on subsequent crops. The use of herbicide safeners can
significantly alleviate herbicide injury to protect crop plants and
expand the application scope of existing herbicides. A series of novel
aryl-substituted formyl oxazolidine derivatives were designed using
the active group combination method. Title compounds were synthesized
using an efficient one-pot method and characterized by infrared (IR)
spectrometry, 1H and 13C nuclear magnetic resonance
(NMR), and high-resolution mass spectrometry (HRMS). The chemical
structure of compound V-25 was further identified by
X-ray single crystallography. The bioactivity assay and structure–activity
relationship proved that nicosulfuron phytotoxicity to maize could
be reduced by most title compounds. The glutathione S-transferase (GST) activity and acetolactate synthase (ALS) in vivo were determined, and compound V-12 showed
inspiring activity comparable to that of the commercial safener isoxadifen-ethyl.
The molecular docking model indicated that compound V-12 competed with nicosulfuron for the acetolactate synthase active
site and that this is the protective mechanism of safeners. Absorption,
distribution, metabolism, excretion, and toxicity (ADMET) predictions
demonstrated that compound V-12 exhibited superior pharmacokinetic
properties to the commercialized safener isoxadifen-ethyl. The target
compound V-12 shows strong herbicide safener activity
in maize; thus, it may be a potential candidate compound that can
help further protect maize from herbicide damage.
4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a pivotal enzyme in tocopherol and plastoquinone synthesis and a potential target for novel herbicides. Thirty-five pyridine derivatives were selected to establish a Topomer comparative molecular field analysis (Topomer CoMFA) model to obtain correlation information between HPPD inhibitory activity and the molecular structure. A credible and predictive Topomer CoMFA model was established by “split in two R-groups” cutting methods and fragment combinations (q2 = 0.703, r2 = 0.957, ONC = 6). The established model was used to screen out more active compounds and was optimized through the auto in silico ligand directing evolution (AILDE) platform to obtain potential HPPD inhibitors. Twenty-two new compounds with theoretically good HPPD inhibition were obtained by combining the high-activity contribution substituents in the existing molecules with the R-group search via Topomer search. Molecular docking results revealed that most of the 22 fresh compounds could form stable π-π interactions. The absorption, distribution, metabolism, excretion and toxicity (ADMET) prediction and drug-like properties made 9 compounds potential HPPD inhibitors. Molecular dynamics simulation indicated that Compounds Y12 and Y14 showed good root mean square deviation (RMSD) and root mean square fluctuation (RMSF) values and stability. According to the AILDE online verification, 5 new compounds with potential HPPD inhibition were discovered as HPPD inhibitor candidates. This study provides beneficial insights for subsequent HPPD inhibitor design.
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