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

Abstract

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.

Modern Approaches for the Development of New Herbicides Based on Natural Compounds

“…Alston. In the study [ 230 ], related methyl ketones carrying electron-donor and acceptor groups or heterocyclic substituents were investigated as the inhibitors of seed germination and growth of seedlings of Amaranthus tricolor L. and E. crus-galli . On the SAR basis, the types and positions of substituents that are crucial for the activity of methyl ketone herbicides were established.…”

“…It was found that indole derivatives, namely 3-acetylindole and 3-acetyl-7-azaindole, are the most active methyl ketones that strongly inhibit plant growth at low concentrations. The molecular docking results indicated the carbonyl, aromatic, and azaindole groups to be important for the interaction of the selected methyl ketones with plant HPPD [ 230 ].…”

Traveling across Life Sciences with Acetophenone—A Simple Ketone That Has Special Multipurpose Missions

“…Furthermore, xanthoxyline showed a significant inhibitory effect on seed germination (15%) and inhibited the root growth (63%) of this annual grassy weed. However, acetophenone ( 1 ) and most of its para -monosubstituted derivatives 12 and 18 – 24 showed weak activity at a concentration of 400 μM on barnyard grass and Chinese amaranth ( Amaranthus tricolor L.) [ 102 ]. Regarding the ortho -monosubstituted acetophenone series, there is little information on its biological properties; however, the remarkable and specific seed germination inhibition effect (~75%, Chinese amaranth) of o -nitroacetophenone ( 25 ) allows us to consider it for the molecular design of new acetophenones that are active against weeds.…”

“…Regarding the ortho -monosubstituted acetophenone series, there is little information on its biological properties; however, the remarkable and specific seed germination inhibition effect (~75%, Chinese amaranth) of o -nitroacetophenone ( 25 ) allows us to consider it for the molecular design of new acetophenones that are active against weeds. Notably, molecular docking on the 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme indicated that these acetophenone derivatives may be involved in key interactions of HPPD inhibitors [ 102 ]. This finding is useful for developing small ketone herbicides.…”

The role of indole derivative in the growth of plants: A review

“…The introduction of the methyl ketone structure at the indole 3-position of compound 24 ( Figure 5 ) produced a considerable inhibition of germination and shoot growth of the seeds of Amaranthus tricolor ( Chotpatiwetchkul et al., 2022 ). At a concentration of 400-800 μM, the germination of seeds was completely inhibited.…”