Antiphytopathogenic Effects and the Preliminary Mechanisms of 5-nitro-8-hydroxyquinoline Derivatives

Introduction: 8-Hydroxyquinoline derivatives are compounds isolated from plants that possess a wide range of pharmacological activities. In our previous work, a series of novel 8- hydroxyquinoline derivatives was synthesized. Among them, the compound 5c, 7-((4-(o-tolyl) piperazine- 1-yl) methyl)-5-nitroquinolin-8-ol, demonstrated broad-spectrum antifungal activity against five plant pathogenic fungi with EC50 values ranging from 4.69 to 12.61 μg/mL. Methods: This investigation principally focused on determining the potential mechanisms of compound 5c using Botrytis cinerea (B. cinerea) as a model. Results: The electron microscope observations revealed that after being treated with compound 5c at 5 μg/mL, the mycelia became obviously curved, collapsed, and its integrity of the cell membrane was eventually destroyed. Discussion: The compound 5c influenced the production of reactive oxygen species, loss of mitochondrial membrane potential, and nuclear morphology. In addition, compound 5c inhibited the enzyme activities related to mitochondrial function. Conclusion: These findings will deepen our insights into the mechanisms of action of 8- hydroxyquinoline against B. cinerea and open new directions for the future development of effective antifungal agents to control phytopathogenic fungi.