Discovery of Topsentin Alkaloids and Their Derivatives as Novel Antiviral and Anti-phytopathogenic Fungus Agents

Topsentin alkaloids and their derivatives were designed, synthesized, and characterized on the basis of NMR and mass spectroscopy. The antiviral activities against tobacco mosaic virus (TMV) and anti-phytopathogenic fungus activities of these alkaloids were evaluated for the first time. Alkaloids 1c, 1e, 2b, and 2d displayed significantly higher antiviral activities against TMV than Ribavirin, emerging as new lead compounds for anti-TMV research. Further fungicidal activity tests against 14 kinds of phytopathogenic fungi revealed that these alkaloids displayed broad-spectrum fungicidal activities. Topsentin derivative 2d with 4-5 mg/kg EC50 values against Sclerotinia sclerotiorum (Lib.), Rhizoctonia solani (Kuhn), and Botrytis cinerea (Pers.) emerged as a new lead compound for fungicidal research. Current studies provide support for the application of topsentin alkaloids as novel agrochemicals.