A new triterpene acid was isolated, together with the known lupeol, bu
tyrospermol, 11 alpha,12 alpha-oxidotaraxerol and 3 beta-hydroxy-30-no
r-lupan-20-one, from the whole herb of Euphorbia chamaesyce. The struc
ture of the new compound was established as 3,4-seco-oleana-4(23),18-d
ien-3-oic acid on the basis of chemical and spectral evidence.