Based on the structural characteristics of the cryptolepine alkaloid, a series of new quindoline derivatives bearing various substituents were prepared and evaluated for their fungicidal and antibacterial activities. Bioassay results showed that compound D7 displayed superior in vitro fungicidal activities against Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium graminearum, and Rhizoctonia solani with EC50 values of 0.780, 3.62, 1.59, and 2.85 μg/mL, respectively. Compound A7 showed apparent antibacterial activities toward Xanthomonas oryzae pv. oryzae with a minimum inhibitory concentration (MIC) value of 3.12 μg/mL. Significantly, in vivo antifungal activity suggested that the curative effect (98.3%) of compound D7 was comparable to that of the positive control azoxystrobin (96.7%) at 100 μg/mL. Preliminary mechanistic studies showed that compound D7 might cause mycelial abnormality of S. sclerotiorum, cell membrane breakage, accumulation of reactive oxygen species (ROS), and inhibition of sclerotia formation. Therefore, compound D7 could be a novel broad-spectrum fungicidal candidate against plant fungal diseases.

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The inhibitory effect of tavaborole on the invasion of Botrytis cinerea in grapes and tomatoes, as well as the potential mechanism involved, was discovered in this study. Our findings showed that tavaborole inhibited Botrytis cinerea spore germination and mycelial expansion in vitro and that the control efficiency in vivo on fruit decay was dose-dependent, which was effective in reducing disease severity and maintaining the organoleptic quality of the fruit, such as reducing weight loss and retaining fruit hardness and titratable acid contents during storage. Furthermore, the precise mechanism of action was investigated further. Propidium iodide staining revealed that Botrytis cinerea treated with tavaborole lost membrane integrity. For further validation, cytoplasmic malondialdehyde accumulation and leakage of cytoplasmic constituents were determined. Notably, the inhibitory effect was also dependent on inhibiting the activities of aminoacyl-tRNA synthetases involved in the aminoacyl-tRNA biosynthesis pathway in Botrytis cinerea. The above findings concluded that tavaborole was effective against Botrytis cinerea infection in postharvest fruit, and a related mechanism was also discussed, which may provide references for the drug repurposing of tavaborole as a postharvest fungicide.

BACKGROUND: The resistance of traditional chemical fungicides to plant pathogenic fungi and the threats to the safety of humans and the environment highlight an urgent need to find safe and efficient alternatives to chemical fungicides. Owing to the wide spectrum of antifungal activities, low persistence and nontoxicity to mammals and aquatic life, essential oils have considerable potential as low-risk pesticides. In this study, the essential oil and the main components of Angelica sinensis (Oliv.) Diels (Danggui) were extracted, analyzed by GC-MS, and evaluated for their antifungal activities against six plant pathogenic fungi.RESULTS: 3-butylidenephthalide (3-BPH) showed the best antifungal activity against Fusarium graminearum with an EC 50 value of 14.35 ∼g mL −1 . The antifungal mechanistic studies revealed that 3-BPH induced the generation of endogenous ROS to cause lipid peroxidation of the cell membrane and inhibited the biosynthesis of ergosterol, thereby causing the cell membrane damaged to exert its fungicidal activity. Significantly, 3-BPH could reduce deoxynivalenol production compared to the control.CONCLUSION: This study demonstrated the potent fungicidal activity of natural phthalide compound 3-BPH and highlighted its potential as an alternative agent to control F. graminearum.