Antifungal activity and mechanistic insights of Panax notoginseng leaf saponins against plant pathogenic fungi

Plants produce secondary metabolites that function as natural defense compounds against pathogens, making them promising sources for environmentally friendly fungicides. We recently identified a sophisticated two-component chemical defense system in Panax notoginseng leaves (PNL), in which the total saponins obtained after enzymatic hydrolysis (TS-a) exhibit more potent antifungal activity compared to non-hydrolyzed counterparts (TS-b). However, the antifungal spectrum of TS-a and its underlying mechanisms have not been systematically characterized. Here, we evaluated the antifungal activity of TS-a against a panel of plant pathogenic fungi. TS-a exhibited broad-spectrum activity and consistently greater potency than TS-b in both in vitro and in vivo assays. Mechanistic investigations showed that TS-a disrupts plasma membrane integrity, promotes reactive oxygen species accumulation, and impairs mitochondrial energy metabolism. These interconnected effects result in membrane damage, metabolic imbalance, and ultimately fungal growth inhibition. Overall, this study demonstrates that TS-a exerts antifungal activity through a multi-target mechanism and displays pathogen-dependent efficacy. These findings highlight the potential of TS-a as a promising candidate for botanical fungicide development and support its application in sustainable crop protection strategies. • TS-a from P. notoginseng leaves exhibits broad-spectrum antifungal activity. • TS-a disrupts fungal membranes and induces severe oxidative stress. • Its multi-target action impairs mitochondrial energy metabolism. • Foliar pathogens are more sensitivity to TS-a than soilborne pathogens. • TS-a shows strong potential as an eco-friendly botanical fungicide.