Synthesis and Antifungal/Oomycetes Activity of Cuminic Acid Derivatives Containing Thiourea Group for Crop Protection.

In search of novel natural product-based fungicides, 24 cuminic acid derivatives containing the thiourea group were synthesized and characterized by 1H, 13C NMR, and HRMS spectra. The antifungal/oomycete activity bioassay showed that some of the title compounds displayed moderate to good antifungal activity against Botryosphaeria dothidea, Sclerotinia sclerotiorum, and Valsa mali. Compound 4k exhibited the best in vitro antifungal activity toward V. mali. The in vivo experiment identified that 4k possessed considerable anti-V. mali protective and curative effect at 200 mg/L. Antifungal mechanism study showed that 4k could destroy the morphology of V. mali mycelia, increase the cell membrane permeability, inhibit the dry weight of V. mali mycelia and lead to the increase of reactive oxygen species (ROS) level. The phytotoxicity experiment revealed that compound 4k showed good safety on mung beans. These cuminic acid derivatives would be potential fungicides for controlling apple canker disease.