Casbane diterpenoids from the roots of Euphorbia pekinensis.

Four casbane diterpenoids, together with three known related compounds were isolated from the roots of Euphorbia pekinensis. Their structures were elucidated on the basis of spectroscopic studies and comparison with the known related compounds. In addition, the absolute configuration of three compounds was determined by the modified Mosher's method. The isolated compounds were evaluated for their cytotoxic activity against seven human cancer cell lines by a WST-8 assay.