Antifungal Application of Rosin Derivatives from Renewable Pine Resin in Crop Protection

In the current work, we synthesized two series of dehydroabietyl amide derivatives from natural product rosin and evaluated their antifungal effects on Valsa mali, Phytophthora capsici, Botrytis cinerea, Sclerotinia sclerotiorum, and Fusarium oxysporum. In vitroand in vivoantifungal activities results indicated that rosin-based amide compounds containing thiophene heterocycles had better inhibitory effects on B. cinerea. In particular, compound 5b(5-fluoro-2-thiophene dehydroabietyl amide) exhibited the excellent antifungal properties against B. cinereawith an EC50of 0.490 mg/L, which was lower compared to the positive control penthiopyrad (0.562 mg/L). Physiological and biochemical studies showed that the primary action mechanism of compound 5bon B. cinereachanges mycelial morphology, increases cell membrane permeability, and inhibits the TCA pathway in respiratory metabolism. Furthermore, QSAR and SAR studies revealed that charge distribution of rosin-based amides derivatives have a key role in the antifungal activity through the hydrogen bonding, conjugation, and electrostatic interaction between the compounds and the receptors of the target. To sum up, this study contributes to the development of rosin-based antifungal agents with a novel structure and preferable biological activity.