Novel flavonoid derivatives containing 1,2,4-triazole Schiff bases as potential antifungal agents: design, synthesis, and biological evaluation.

A series of flavonol derivatives containing 1,2,4-triazole Schiff base was designed, synthesized and tested for their biological activities. The results of the biological activity test showed that compounds exhibited the obvious antifungal activities against Sclerotinia sclerotiorum (S.s), Rhizoctonia solani (R.s), Botrytis cinerea (B.c) and Phomopsis sp (P.s). Among them, K14 showed excellent antimicrobial activity against B.c with the half maximal effective concentration (EC) of 7.6 µg/mL as compared to azoxystrobin (18.0 µg/mL). Additionally, the in vivo protective and therapeutic activities of K14 on blueberry leaves were 94.1 and 88.7 % respectively, surpassing than that of the control drug azoxystrobin (91.6 and 74.4 %) at 200 µg/mL. The results of SEM showed that the mycelium appeared wrinkled, folded and changed in morphology after being treated with K14. In addition, fluorescence microscopy (FM) and cytoplasmic leakage assays showed that the cell membrane of B.c was disrupted. Further study of malondialdehyde (MDA) and relative conductivity measurements indicated that the normal function of cells is affected by K14 by increasing cell membrane permeability and promoting membrane lipid peroxidation. These results indicate that flavonol derivatives containing 1,2,4-triazole Schiff bases are expected to provide a new prospect for the development of novel fungicides.