Design, Synthesis, and Antimicrobial Activity of Quindoline Derivatives Inspired by the Cryptolepine Alkaloid.

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 displayed superior fungicidal activities against , , , and with EC values of 0.780, 3.62, 1.59, and 2.85 μg/mL, respectively. Compound showed apparent antibacterial activities toward with a minimum inhibitory concentration (MIC) value of 3.12 μg/mL. Significantly, antifungal activity suggested that the curative effect (98.3%) of compound was comparable to that of the positive control azoxystrobin (96.7%) at 100 μg/mL. Preliminary mechanistic studies showed that compound might cause mycelial abnormality of , cell membrane breakage, accumulation of reactive oxygen species (ROS), and inhibition of sclerotia formation. Therefore, compound could be a novel broad-spectrum fungicidal candidate against plant fungal diseases.