Abstract: The perennial herbaceous plant Euphorbia jolkinii(Euphorbiaceae) is a noxious weed widely distributed in the grasslands of northwestern Yunnan and has greatly threatened the local biodiversity. Phytochemical investigation on the fresh roots of E. jolkinii afforded six new diterpenoids 1, 2, 4-6, and 8, together with fifteen known diterpenoids. Their structures were elucidated on the basis of 1D and 2D NMR and other spectroscopic methods. Casbane, lathyrane, abietane, and ent-kaurane diterpenoids were reported from this plant for the first time. Selected compounds were evaluated for their antifeedant and anti-RSV(respiratory syncytial virus) activities. Compound 2 and ingenol(3) exhibited moderate antifeedant activity against a generalist insect herbivore, Spodoptera exigua, with EC₅₀ values of 17.88 and 17.71 lg/cm² respectively. Compound 19 showed significant anti-RSV activity, with 50% inhibition(IC₅₀) value of 10.0 μM and selective index of 8.0. Compounds 1 and 2 were less active against RSV virus, both with IC₅₀ value of 25 μM, and with selective indices of 1.0 and 3.2 respectively. These findings provided new evidence for the biological functions and utilization of the diversified diterpenoid metabolites in the roots of this rich but harmful plant.

Key words: Euphorbia jolkinii, Diterpenoids, Antifeedant activity, Antiviral activity

摘要： The perennial herbaceous plant Euphorbia jolkinii(Euphorbiaceae) is a noxious weed widely distributed in the grasslands of northwestern Yunnan and has greatly threatened the local biodiversity. Phytochemical investigation on the fresh roots of E. jolkinii afforded six new diterpenoids 1, 2, 4-6, and 8, together with fifteen known diterpenoids. Their structures were elucidated on the basis of 1D and 2D NMR and other spectroscopic methods. Casbane, lathyrane, abietane, and ent-kaurane diterpenoids were reported from this plant for the first time. Selected compounds were evaluated for their antifeedant and anti-RSV(respiratory syncytial virus) activities. Compound 2 and ingenol(3) exhibited moderate antifeedant activity against a generalist insect herbivore, Spodoptera exigua, with EC₅₀ values of 17.88 and 17.71 lg/cm² respectively. Compound 19 showed significant anti-RSV activity, with 50% inhibition(IC₅₀) value of 10.0 μM and selective index of 8.0. Compounds 1 and 2 were less active against RSV virus, both with IC₅₀ value of 25 μM, and with selective indices of 1.0 and 3.2 respectively. These findings provided new evidence for the biological functions and utilization of the diversified diterpenoid metabolites in the roots of this rich but harmful plant.

关键词: Euphorbia jolkinii, Diterpenoids, Antifeedant activity, Antiviral activity