High Value-Added Application of Natural Products in Crop Protection: Discovery and Exploration of Caffeoyl and Flavonoid Derivatives from DC. as Novel Insecticide Candidates.

Nine caffeoyl derivatives (), including two new dicaffeoyl glycosides, brevicaudatosides A and B ( and ), and six flavonoids (), were identified from overground DC. Compounds and exhibited significant oral toxicities against Harris with LC (half-lethal concentration) values of 0.12 and 0.28 mM, respectively. Meanwhile, compounds , , , , and showed remarkable repellent effects against with the repellent indexes valued at 1.00 under 50-200 μg/mL at 24 h. Compounds and also displayed moderate antifeedant activities against L. The shrunken bodies, especially for wizened cauda, and the ultrastructural damages of microvilli, mitochondrion, nucleus, and endoplasmic reticulum in midgut were toxic symptoms of caused by and . The inhibition of Chitinase was the main reason for their potent insecticidal activities. This study provided valuable pieces of evidence for the high value-added application of caffeoyl and flavonoid derivatives from as novel plant-origin biopesticides for crop protection.