Fungicidal Activity and Mechanism of Action of Glabridin from Glycyrrhiza glabra L.

Glycyrrhiza glabra (Licorice) belongs to the Fabaceae family and its extracts have exhibited significant fungicidal activity against phytopathogenic fungi, which has mainly been attributed to the presence of phenolic compounds such as flavonoids, isoflavonoids and chalcones. In this study, a series of licorice flavonoids, isoflavonoids and chalcones were evaluated for their fungicidal activity against phytopathogenic fungi. Among them, glabridin exhibited significant fungicidal activity against ten kinds of phytopathogenic fungi. Notably, glabridin displayed the most active against Sclerotinia sclerotiorum with an EC50 value of 6.78 µg/mL and was 8-fold more potent than azoxystrobin (EC50, 57.39 µg/mL). Moreover, the in vivo bioassay also demonstrated that glabridin could effectively control S. sclerotiorum. The mechanism studies revealed that glabridin could induce reactive oxygen species accumulation, the loss of mitochondrial membrane potential and cell membrane destruction through effecting the expression levels of phosphatidylserine decarboxylase that exerted its fungicidal activity. These findings indicated that glabridin exhibited pronounced fungicidal activities against S. sclerotiorum and could be served as a potential fungicidal candidate.