Synthesis, Antiviral Activity, and Induction of Plant Resistance of Indole Analogues Bearing Dithioacetal Moiety

Abstract

A series of compounds with potential activity to induce plant resistance was synthesized from indole and thiol compounds and methodically evaluated for antiviral activity. The results indicated that some of the synthesized compounds had high antipotato virus Y (PVY), anticucumber mosaic virus, and antitobacco mosaic virus activities. Notably, compound <b>D21</b> exhibited the best activity against PVY among these compounds in vivo, and the 50% effective concentrations (EC₅₀) of protection activity is 122 μg/mL, which was distinctively better than the corresponding values for ribavirin (653 μg/mL), Ningnanmycin (464 μg/mL), and Xiangcaoliusuobingmi (279 μg/mL). Interestingly, we found that the protection activity of <b>D21</b> was associated with improvement of chlorophyll content and defense-related enzyme activities. Moreover, <b>D21</b> could trigger the malate dehydrogenase (MDH) signaling pathway, as further confirmed by the MDH activity evaluation. Hence, <b>D21</b> can protect plants against viral activity and has potential as a novel activator for plant resistance induction.