Isolation and insecticidal activity of sesquiterpenes alkaloids from Tripterygium wilfordii Hook f.

• Seven sesquiterpenes alkaloids from Tripterygium wilfordii root bark were isolated and identified.
• Most of the seven alkaloids showed insecticidal activity to four species of insect pests.
• Wilforine was the main insecticidal constituent among the seven alkaloids.
• This is the first report of insecticidal activity of 1-desacetylwilforgine and 1-desacetylwilforine.

The isolation of compounds produced by secondary metabolism of plants can lead to the discovery of new insecticidal agents. In light of this possibility, we isolated seven sesquiterpenes alkaloids from an ethanolic extract of Tripterygium wilfordii (Celastraceae) root bark, an important Chinese medicinal species. These were identified as wilforjine, 1-desacetylwilforgine, wilforgine, 1-desacetylwilforine, wilforine, wilfortrine and peritassines A. To characterize their biological activities, bioassays were conducted using different insect pest species of medical and agricultural importance. Wilforgine, 1-desacetylwilforine, and wilforine showed strong antifeedant effects to 3rd instar larvae of both Mythimna separata Walker (Lepidoptera: Noctuidae) (DC50 = 17.68, 33.52 and 4.10 μg/ml, respectively) and Plutella xylostella L. (Lepidoptera: Plutellidae) (DC50 = 54.62, 55.19 and 36.65 μg/ml, respectively) as well as knockdown activity in 3rd instar larvae of both M. separata (EC50 = 630.30, 212.17 and 100.89 μg/ml, respectively) and P. xylostella (EC50 = 177.51, 336.59 and 97.77 μg/ml, respectively). Moreover, 1-desacetylwilforgine, wilforgine, 1-desacetylwilforine, and wilforine showed insecticidal activity to 3rd instar larvae of Culex pipiens pallens Coquillett (Diptera: Culicidae) (LC50 = 25.70, 25.40, 22.58 and 14.57 μg/ml, respectively) and adults of Musca domestica L. (Diptera: Muscidae) (LC50 = 87.29, 70.19, 47.80 and 21.00 μg/ml, respectively). In general, wilforine was the most active sesquiterpene alkaloid isolated from T. wilfordii root bark. This is also the first report of insecticidal activity of 1-desacetylwilforgine and 1-desacetylwilforine. The potential use of T. wilfordii derivatives in botanical insecticides is discussed.