Fabrication of Dimeric Prodrug Self-Assembly for Efficient Utilization of Aldehyde-Containing Plant Essential Oils in Management of Plant Disease

The dimeric prodrug self-assembly (DPSA) technology, with a simple preparation process, high drug-loading capacity, and excellent safety, could provide an innovative solution to address issues, including the poor stability and low bioavailability of aldehyde-containing plant essential oils (APOs) in agricultural applications. Herein, dimeric prodrugs based on APOs salicylaldehyde (Sal) and citral (Cit) were fabricated by individually conjugating Sal and Cit with oxalyl dihydrazide (Oxa) through a simple Schiff base reaction and subsequently self-assembled into nanoparticles (Sal-Oxa NPs and Cit-Oxa NPs) in aqueous solution for improving the stability and biological activity of APOs. The results showed that a pH of 7 and a temperature of 25 °C were the optimal conditions for the formation of DPSA with superior colloidal stability. The obtained DPSA exhibited excellent physicochemical properties, including low volatility and surface tension, and high photostability, thermal stability, and maximum retention, significantly improving the wettability, adhesion, and deposition of Sal and Cit on different plant leaves. Importantly, DPSA could be decomposed in acidic environments caused by pathogenic fungi to controllably release Sal, Cit, and Oxa to exert multitarget synergistic effects on plant disease. Moreover, DPSA demonstrated better biosafety to tomato and Vicia faba, comparable to that of APOs. Therefore, this study would provide a promising strategy for efficient utilization of APOs in the effective control of plant diseases.