Design, Synthesis, and Antimicrobial Activity Evaluation of Novel Isocryptolepine Derivatives against Phytopathogenic Fungi and Bacteria.

This research adopted the Fischer indole synthesis method to continue constructing a novel drug-like chemical entity based on the guidance of isocryptolepine and obtained four series of derivatives: , , , and . The antimicrobial activity of these derivatives against plant pathogens was further evaluated. The results showed that had the best antifungal effect against , and its EC value was up to μg/mL. In addition, an in vivo activity test showed that the protective effect of on apples was 82.2% at 200 μg/mL, which was better than that of Pyrimethanil (45.4%). Meanwhile, it was found by scanning electron microscopy and transmission electron microscopy that the compound affected the morphology of mycelia. The compound was found to damage the cell membrane by PI and ROS staining. Through experiments such as leakage of cell contents, it was found that the compound changed the permeability of the cell membrane and caused the leakage of substances in the cell. According to the above studies, compound can be used as a candidate lead compound for further structural optimization and development.