Semi‐synthesis and characterization of some new matrine derivatives as insecticidal agents

Abstract BACKGROUND Matrine is an important traditional plant‐derived insecticide with broad‐spectrum activity. However, due to its moderate activity, matrine is mainly applied in combination with other pesticides. In order to discover new potential natural‐product‐based crop protection agents, a series of matrine derivatives characterized by cyclohexylamine group were synthesized to screen their insecticidal activity against seven typically agricultural pests. RESULTS The structural configurations of compounds were characterized by IR, 1 H NMR, 13 C NMR, MS and XRD, with the pure yields of 42%, 65% and 71%, respectively. Although all compounds showed poor insecticidal activity against five lepidoptera pests, the compounds 2 and 4 displayed remarkable insecticidal activities against Lipaphis erysimi and Mulberry Root‐Knot Nematode with a concentration‐dependent manner within 0.5~1.5 mg/ mL. Compared with matrine (60%), compounds 2 and 4 exhibited potent insecticidal activities against L. erysimi , with a corrected mortality of 83.3% and 89.7%, respectively. They also showed excellent control effects on Mulberry Root‐Knot Nematode , with corrected mortality as high as 88% and 80%, respectively. CONCLUSION All four synthesized matrine derivatives showed poor insecticidal activity against five lepidoptera pests, but the compounds 2 and 4 exhibited much stronger insecticidal activities against L. erysimi and Mulberry Root‐Knot Nematode than matrine. Combined with the structural characteristics of compounds 1~4, we conclude that 4‐methylcyclohexylamine, not the carbon disulfide group or cyclohexylamine group alone, mainly contributed to the improvement of insecticidal activities of matrine derivatives against these two agricultural pests. This work provides a direction and foundation for structural optimization of the matrine pesticides in the future. © 2020 Society of Chemical Industry