Preparation and Biological Evaluation of Novel Osthole-Derived -Benzoylthioureas as Insecticide Candidates.

To discover novel natural-product-based insecticide candidates, herein, a variety of osthole-derived -benzoylthioureas were synthesized and assessed for their insecticidal activities against three insect pests. An insecticidal assay showed that most of the target osthole-derived -benzoylthioureas displayed a more potent and broad-spectrum insecticidal effect than the parent osthole after the introduction of -benzoylthioureas on the C-3' position of osthole. Compound displayed the most potent growth inhibitory (GI) effect on Walker, with a final corrected mortality rate of 82.1% when treated with a concentration of 1 mg/mL, which was 1.64- and 1.53-fold higher in comparison to osthole and the botanical insecticide toosendanin, respectively. Compounds , , and displayed a more promising aphicidal effect on Sulzer, and their LD values were 0.015, 0.017, and 0.019 μg/larvae, respectively, superior to the commercially available insecticide rotenone (0.024 μg/larvae). Derivatives , , , and displayed more potent larvicidal activity against Linnaeus, with LC values of 0.22, 0.26, 0.15, and 0.30 mg/mL, respectively, exceeding that of rotenone (0.37 mg/mL). Furthermore, both compounds and against were found to be more effective than rotenone in a control efficacy assay under greenhouse conditions. The structure-activity relationship (SAR) suggested that osthole-derived -benzoylthioureas are more active in most cases when the R group is an electron-withdrawing group than when it is an electron-donating group, especially for halogenated groups. Additionally, the potent compounds and possessed good selectivity and were less toxic to non-target organisms. This study suggests that these osthole-derived -benzoylthioureas could be further studied in depth as eco-friendly natural product pesticides in crop protection.