Feruloyl-amides as natural antimicrobials for crop and food protection

Pyricularia oryzae is a major biotic threat constraining rice production worldwide. The increasing concern over the environmental impact of fungicide resistance spread in pathogens, and growing demand for sustainable crop protection and food safety solutions is driving interest in plant-derived bioactive compounds. Such natural and naturally derived compounds represent promising tools for integrated fungal disease management in crops. Phenylamides (PAs), naturally occurring in many plants including rice, are known for their involvement in plant defense. A set of ferulic acid-derived PAs was synthesized via chemical and chemoenzymatic approaches to evaluate their antifungal potential against Pyricularia oryzae, other key phytopathogens: Botrytis cinerea , Fusarium culmorum. Antifungal activity was assessed through inhibition of mycelial growth, spore germination, and, in the case of P. oryzae, appressorium formation—a critical structure for host penetration and disease establishment. A striking inhibitory effect on P. oryzae appressorium formation was observed for specific PAs; some significantly reduced appressorium development by up to 94% without affecting spore germination, suggesting a targeted disruption of virulence mechanisms rather than general antifungal toxicity. Structure-activity relationships indicated that the presence of hydroxyl- and guanidine- groups enhanced efficacy. Overall, the synthesized compounds showed modest effects on mycelial growth, with inhibition rates up to 25% in F. culmorum. Spore germination in B. cinerea and mycelial growth in P. oryzae was largely unaffected, indicating that these compounds do not interfere with early fungal development. These findings suggest that phenylamides may act by impairing fungal infection processes than inhibiting vegetative growth, offering a novel mechanism for disease control.