Design, synthesis and biological activity of chalcone derivatives containing pyridazine

Inspired by the application of fungicide from natural products, a series of chalcone derivatives containing pyridazine were designed, synthesized, and evaluated for their antifungal activities against nine plant fungi and antibacterial activity against three plant bacteria. The antibacterial results revealed that B8 showed the best activity against Xanthomonas campestris pv. citri (Xac) with an EC50 value of 78.89 μg/mL, superior to Bismerthiazol (EC50 = 86.72 μg/mL). The antifungal bioactivity results showed that some of the compounds had good bioactivity against fungi, such as B4 showed the best bioactivity against Botrytis cinerea (BC) with an EC50 value of 8.91 μg/mL, which was better than the azoxystrobin (EC50 = 20.28 μg/mL). Compounds B4, D2 and D3 showed good biological activity against Rhizoctonia solani (RS), with an EC50 value of 18.10, 20.18 and 20.60 μg/mL, comparable to the azoxystrobin. Antifungal mechanism studies of BC by B4 suggest that B4 disrupts the cell membrane of the mycelium and thus inhibits the growth of the fungus. The above indicates that chalcone derivatives containing pyridazine have the potential to become fungicides.