Novel Galactosyl Moiety-Conjugated Furylchalcones Synthesized Facilely Display Significant Regulatory Effect on Plant Growth

Synthesis and Evaluation of New Phytotoxic Fluorinated Chalcones as Photosystem II and Seedling Growth Inhibitors

The development of novel phytotoxic compounds has been an important aim of weed control research. In this study, we synthesized fluorinated chalcone derivatives featuring both electron-donating and electron-withdrawing groups. These compounds were evaluated both as inhibitors of the photosystem II (PSII) electron chain as well as inhibitors of the germination and seedling growth of Amaranthus plants. Chlorophyll a (Chl a) fluorescence assay was employed to evaluate their effects on PSII, while germination experiments were conducted to assess their impact on germination and seedling development. The results revealed promising herbicidal activity for (E)-3-(4-bromophenyl)-1-(4-fluorophenyl)prop-2-en-1-one (7 a) and (E)-1-(4-fluorophenyl)-3-phenylprop-2-en-1-one (7 e). Compounds 7 a and 7 e exhibited a reduction in Chl a parameters associated with performance indexes and electron transport per reaction center. This reduction suggests a decrease in PSII activity, attributed to the blockage of electron flow at the quinone pool. Molecular docking analyses of chalcone derivatives with the D1 protein of PSII revealed a stable binding conformation, wherein the carbonyl and fluorine groups interacted with Phe265 and His215 residues, respectively. Additionally, at a concentration of 100 μM, compound 7 e demonstrated pre- and post-emergent herbicidal activity, resulting in a reduction of the seed germination index, radicle and hypocotyl lengths of Amaranthus weeds.

Fungicidal activity of novel quinazolin-6-ylcarboxylates and mode of action on Botrytis cinerea

BACKGROUND

Fungal diseases remain important causes of crop failure and economic losses. As the resistance toward current selective fungicides becomes increasingly problematic, it is necessary to develop efficient fungicides with novel chemotypes.

RESULTS

A series of novel quinazolin-6-ylcarboxylates which combined the structures of pyridine or heterocyclic motif and the N-(3-chloro-4-fluorophenyl)quinazolin-4-amine moiety, a binding group of ATP-binding site of gefitinib, were evaluated for their fungicidal activity on different phytopathogenic fungi. Most of these compounds showed excellent fungicidal activities against Botrytis cinerea and Exserohilum rostratum, especially compound F17 displayed the highest activity with EC50 values as 3.79 μg mL-1 against B. cinerea and 2.90 μg mL-1 against E. rostratum, which was similar to or even better than those of the commercial fungicides, such as pyraclostrobin (EC50 , 3.68, 17.38 μg mL-1 ) and hymexazol (EC50 , 4.56, 2.13 μg mL-1 ). Moreover, compound F17 significantly arrested the lesion expansion of B. cinerea infection on tomato detached leaves and strongly suppressed grey mold disease on tomato seedlings in greenhouse. The abilities of compound F17 to induce cell apoptosis of the non-germinated spores, to limit oxalic acid production, to reduce malate dehydrogenase (MDH) expression, and to block the active pocket of MDH protein were demonstrated in B. cinerea.

CONCLUSION

The novel quinazolin-6-ylcarboxylates containing ATP-binding site-directed moiety, especially compound F17, could be developed as a potential fungicidal candidate for further study. © 2023 Society of Chemical Industry.

The importance of selecting crystal form for triazole fungicide tebuconazole to enhance its botryticidal activity

The growing evidences of resistant fungi stimulate fully understanding tebuconazole regarding its crystal structure on fungicidal activity. In this study, the crystal structures of six technical tebuconazoles (BX, HH, JP, QZ, SJ, and YT) were characterized by using high-resolution X-ray powder diffraction and three-dimensional crystal structure modeling. A structure-activity relationship of the tebuconazoles on the susceptible (HLS and YJS) or resistant (XHR) Botrytis cinerea isolates was analyzed, the differential tricarboxylic acid (TCA) cycle metabolism was determined, and molecular docking with sterol 14α-demethylase (CYP51) was performed. The results showed that tebuconazole existed in three types of crystal forms: an overlapping-pair conformation, a side-by-side-pair conformation, and a parallel-pair conformation. QZ with the parallel-pair conformation and the minimum crystal cell volume exhibited a higher activity and a lower resistant level. XHR possessed a higher content of TCA cycle metabolites and phosphate than YJS, but the exposure to QZ significantly reduced the contents of citrate, isocitrate, α-ketoglutarate and oxaloacetate in XHR, as did the exposure to other technical tebuconazoles. Moreover, the point mutations F487L, G464S, and G443S altered the binding properties of chiral stereoscopic R-QZ with CYP51 protein. Especially the G443S mutation promoted a weak linking of R-QZ with LEU380 and TYR126, and greatly slashed the binding action at lower docking score. In conclusion, our results evidenced an efficient crystal conformation of tebuconazole to improve botryticidal activity and a potential adaptability of B. cinerea to tebuconazole inhibition in TCA cycle metabolism and CYP51 protein mutation.

Structure-Activity Relationship Study of Xanthoxyline and Related Small Methyl Ketone Herbicides

Xanthoxyline (1), a small natural methyl ketone, was previously reported as a plant growth inhibitor. In this research, related methyl ketones bearing electron-donating and electron-withdrawing groups, together with heteroaromatics, were investigated against seed germination and seedling growth of Chinese amaranth (Amaranthus tricolor L.) and barnyard grass [Echinochloa crus-galli (L.) Beauv]. The structure-activity relationships (SARs) of methyl ketone herbicides were clarified, and which types and positions of substituents were crucially important for activity were also clarified. Indole derivatives, namely, 3-acetylindole (43) and 3-acetyl-7-azaindole (44) were found to be the most active methyl ketones that highly suppressed plant growth at low concentrations. The molecular docking on the 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme indicated that carbonyl, aromatic, and azaindole were key interactions of HPPD inhibitors. This finding would be useful for the development of small ketone herbicides.