Synthesis of novel strigolactone analogues with 2,3-dihydroquinolin-4(1H)-one scaffold and efficacy for the Phelipanche aegyptiaca

As an annual holoparasitic weed, Phelipanche aegyptiaca is widely distributed in the northwest area of China, primarily parasitizing solanaceous crops such as tomato and potato. Currently, there is no effective herbicide for controlling P. aegyptiaca. Based on the seed germination property of natural strigolactones, herein we synthesized a series of strigolactone analogues derived from 2,3-dihydroquinolin-4(1H)-one scaffold applied to P. aegyptiaca control. Compounds 5a, 5b, 5i, 5m, and 5n showed higher bioactivity than the positive control rac-GR24 (EC₅₀ = 0.04158 mg/L). Particularly, compound 5m (EC₅₀ = 0.00358 mg/L) displayed a 12-fold higher seed germination activity than rac-GR24 towards the parasitic P. aegyptiaca seeds. The greenhouse experiment revealed that compound 5m exhibited a robust potential in P. aegyptiaca control. Compared to the control group (13.60 per pot), the number of P. aegyptiaca plant infected to the tomato plant crashed to 1.62 per pot at the dosage of 10 mg/L. Finally, to better understand the structure-activity relationship on these novel quinoline-4-one derivatives, we performed molecular docking of compound 5m. The results of this study provide a promising basis for using quinoline-4-one-derived strigolactone analogues for the P. aegyptiaca control.