Discovery of Natural Rosin-Based Herbicide Agent to Control Echinochloa crusgalli for Sustainable Weed Management

Natural rosin derivatives offer a promising scaffold for developing low-toxicity herbicides to address environmental concerns triggered by synthetic agrochemicals. In this research, a series of dehydroabietyl-hydrazide-based derivatives (3a-l) were synthesized using dehydroabietic acid as a lead compound. The herbicidal activities of these derivatives were evaluated against Echinochloa crusgalli, Sorghum halepense, Portulaca oleracea, and Amaranthus caudatus L. weeds. The result indicated that 3e exhibited broad-spectrum activity, particularly against barnyard grass root growth, with 91.0% inhibition at 100 μg/mL, outperforming the commercial herbicides naptalam (NPA) and glyphosate. Subsequently, the physiological indicators were employed to reveal the mode of action of 3e, and the result suggested that 3e significantly inhibited peroxidase enzyme activity, reduced the level of growth-promoting hormones, and increased the inhibitory hormone content, ultimately disrupting endogenous hormone homeostasis. Molecular docking demonstrated that 3e stably bound to the POD (-7.73 kcal/mol) via synergistic hydrogen bonding and hydrophobic actions. Crop safety assessments showed that 3e presented lower toxicity to wheat, corn, rice, and cotton seedlings at a high concentration of 200 g a.i./ha. The biosafety assessment evaluation also suggested that 3e showed lower toxicity to zebrafish, with 96 h median lethal concentration values of 33.9 μg/mL. Overall, these findings suggested that 3e could serve as a natural herbicide agent for controlling E. crusgalli, offering a sustainable weed management strategy.