Antifungal mechanism of eudesmane sesquiterpenoid glycosides from the fruits of Pittosporum kweichowense against Sclerotinia sclerotiorum.

BACKGROUND: Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) de Bary, is among the most destructive crop diseases worldwide. This study aimed to identify novel antifungal agents from Pittosporum kweichowense and elucidate their mechanisms against this pathogen. RESULTS: Six eudesmane-type sesquiterpenoid glycoside esters (ESGEs) were isolated from the fruit of P. kweichowense, including four new compounds pitkweifrucosides A-D (1-4), and two known analogs (5-6). Their structures were established by spectroscopic analyses and comparison with authentic samples. Compound 5 (Pitsubcoside H, PS-H) showed potent antifungal activity against S. sclerotiorum with a median effective concentration of 38.61 μg mL-1. At 100 μg mL-1, PS-H inhibited mycelial growth and reduced sclerotial formation by 75.00%. It also delayed sclerotial germination at early stages and decreased oxalic acid production by 73.08%. TEM observation confirmed disruption of cellular integrity. Transcriptomic and metabolomic analyses further revealed that PS-H exerts antifungal effects primarily through perturbation of amino acid metabolism and ribosomal function. CONCLUSION: This study demonstrates that PS-H exhibits significant antifungal activity against S. sclerotiorum via disruption of key metabolic pathways. These findings provide a solid basis for developing this compound as a sustainable, low-toxicity alternative to conventional fungicides. © 2026 Society of Chemical Industry.