Antifungal Activity and Mechanistic Insights of 1-O-Alkylglycerols against Monilinia fructigena

Peach brown rot, caused by Monilinia fructigena (M. fructigena), is a destructive disease that affects peaches during pre- and postharvest stages. In this study, two 1-O-alkylglycerols (AKGs), namely, AKG-2 (1-O-dodecylglycerol) and AKG-4 (3-(2-ethylhexyloxy)propane-1,2-diol), demonstrated significant in vitro antifungal activity against M. fructigena, with EC50 values of 102 and 103 μg/mL, respectively. At a concentration of 200 μg/mL, both compounds effectively suppressed brown rot symptoms in inoculated peaches, achieving a protective efficacy of 93.2%. Mechanistic investigations revealed that AKG-2 and AKG-4 disrupted the surface morphology and internal ultrastructure of fungal hyphae, compromised the integrity of the cell membrane and nucleus, and reduced mitochondrial membrane potential. Moreover, treatment with these compounds induced the accumulation of reactive oxygen species, leading to elevated malondialdehyde levels and decreased activities of key antioxidant enzymes including superoxide dismutase and catalase. These results suggest that AKG-2 and AKG-4 exhibit antifungal effects through multiple synergistic mechanisms including membrane and nuclear damage, mitochondrial dysfunction, and oxidative stress induction. This study, for the first time, provides valuable mechanistic insights into the antifungal effects of AKGs and supports their potential as naturally derived fungicidal agents for the protection of peach fruits.