Insecticidal activity of sesquiterpene lactones and monoterpenoid from the fruits of Carpesium abrotanoides

• Two new sesquiterpene lactones 1 and 2 were isolated from Carpesium abrotanoides.
• Insecticidal activities of compounds 1–7 were studied for the first time.
• Compound 1 showed the strongest activity against the two pests.
• C. abrotanoides is a promising source of botanical insecticides.

The isolation of secondary metabolites produced by plants can lead to the discovery of new insecticidal agents. The aim of this study was to identify secondary metabolites from the fruits of Carpesium abrotanoides, a well-known medicinal and poisonous plant belonging to the family Asteraceae, with the potential to act as natural insecticides. Two new sesquiterpene lactones 9β-hydroxy-1βH, 11αH-guaia-4,10(14)-dien-12,8α-olide (1) and 9β-hydroxy-1βH, 11βH-guaia-4,10(14)-dien-12,8α-olide (2) along with four known sesquiterpene lactones (3-6) and one monoterpenoid (7) have been isolated. The structures of these compounds were established on the basis of 1D and 2D NMR data and HRESIMS data interpretation. To characterize their insecticidal activities, bioassays were conducted using two insect pest species of agricultural importance. Compounds 1–7 showed antifeedant effects to 3rd instar larvae of Plutella xylostella (Lepidoptera: Plutellidae) in a concentration-dependant manner with EC50 of 19.84, 42.82, 97.94, 96.90, 39.94, 37.35 and 43.99 mg/L, respectively. Moreover, all of these compounds display stomach-contact combination toxicity toward 4rd instar larvae of Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae) (LD50 = 18.71, 80.29, 230.65, 319.67, 31.18, 40.87 and 68.47 mg/L, respectively). In general, this is the first report of insecticidal activities of secondary metabolites isolated from C. abrotanoides. Moreover, compound 1 showed the best insecticidal activity in the test, demonstrating its potential to be used as a natural insecticides.