Bioactive isopimarane diterpenoids from the stems of Euonymus oblongifolius

Seven isopimarane diterpenes and one abietane diterpene, together with six known sesquiterpene derivatives, were isolated from the stems of Euonymus oblongifolius. Their structures were elucidated on the basis of spectroscopic analyses, and the absolute configuration of euonymusisopimaric acid A was confirmed by single-crystal X-ray crystallographic analysis using anomalous scattering of Cu Kα radiation. All of the isolated compounds were evaluated for their ability to inhibit LPS-induced nitric oxide production in the murine microglia BV2 cell line, and for their cytotoxic activity against five human cancer cell lines. Euonymusisopimaric acids A, E and F inhibited LPS-induced nitric oxide production in the murine microglia BV2 cell line, with IC₅₀ values of 2.4, 4.8, and 1.6 μM, respectively. Euonymusisopimaric acid B exhibited moderate cytotoxicity against A549 cell line growth, with an IC₅₀ value of 2.6 μM.