Evolution from Natural <i>β</i>-Carboline Alkaloids to Obtain 1,2,4,9-tetrahydro-3-thia-9-aza-fluorene Derivatives as Potent Fungicidal Agents against <i>Rhizoctonia solani</i>

• Main Authors: Junmin Xi, Zhijun Zhang, Qi Zhu, Guohua Zhong
• Format: Article
• Language: English
• Published: MDPI AG 2018-12-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>β</i>-carboline; 1,2,4,9-tetrahydro-3-thia-9-azafluorene; fungicidal activity; <i>Rhizoctonia solani</i>
• Online Access: https://www.mdpi.com/1422-0067/19/12/4044

Rice sheath blight, caused by <i>Rhizoctonia solani</i>, is a globally important rice disease and the increasing resistance of this pathogen highlights the need for new active compounds against rice sheath blight. In this study, natural <i>&#946;</i>-carboline alkaloids were optimized to obtain a series of 1,2,4,9-tetrahydro-3-thia-9-aza-fluorene derivatives and evaluated for their fungicidal activity and mode of action against <i>R. solani</i>. Of these compounds, <b>18</b> exhibited significant in vitro fungicidal activity against <i>R. solani</i>, with an EC₅₀ value of 2.35 &#956;g/mL, and was more active than validamycin A. In vivo bioassay also demonstrated that <b>18</b> displayed superior protective and curative activities as compared to validamycin A. Mechanistically, <b>18</b> not only induced the loss of mitochondrial membrane potential and accumulation of reactive oxygen species, but also interfered with DNA synthesis. Therefore, compound <b>18</b> displayed pronounced in vitro and in vivo fungicidal activity against <i>R. solani</i> and could be used as a potential candidate for the control of rice sheath blight.