Discovery and Structural Optimization of 1,2,3,4-Tetrahydro-beta-carbolines as Novel Reactive Oxygen Species Inducers for Controlling Intractable Plant Bacterial Diseases

Nowadays, reactive oxygen species (ROS) have been acknowledged as promising bactericidal targets against pesticide-resistant bacteria. Herein, to further excavate more excellent ROS inducers, simple 1,2,3,4-tetrahydro-beta-carboline derivatives containing a 3-aminopropanamide moiety were prepared and assessed for their antibacterial potency. Notably, three promising compounds displayed significant antibacterial potency. Compound I-29 exhibits excellent in vitro bioactivity, with an EC50 value of 5.73 mu g/mL, and admirable in vivo activities (protective activity of 55.74% and curative activity of 65.50%) toward Xanthomonas oryzae pv. oryzae. Compound I-16 has good activity in vitro, with an EC50 of 3.43 mu g/mL, and outstanding bioactivities in vivo (protective activity of 92.50% and curative activity of 59.68%) against Xanthomonas axonopodis pv. citri. Compound I-6 shows excellent in vitro bioactivity (EC50 = 2.86 mu g/mL) and significant protective activity (94.02%) for preventing Pseudomonas syringae pv. actinidiae. Antibacterial mechanism investigations indicate that these compounds disrupt the balance of the redox system to kill bacteria. These simple 1,2,3,4-tetrahydro-beta-carboline derivatives are promising leads to the discovery of bactericidal agents.