Abstract:The aerial parts of Siegesbeckia have been used as the traditional Chinese medicine in the treatment of rheumatic arthritis, hypertension, malaria, neurasthenia, and snakebite. In order to find new and bioactive compounds, the chemical constituents of the aerial parts of S. orientalis L. were investigated and two new compounds, namely β-D-glucopyranosyl-ent-2-oxo-15,16-dihydroxy-pimar-8(14)-en-19-oic-late (compound 1) and [1(10)E,4Z]-8β-angeloyloxy-9α-methoxy-6α,15-dihydroxy-14-oxogermacra-1(10),4,11(13)-trien-12-oic acid 12,6-lactone (compound 2), as well as five known ent-pimarane diterpenes (compounds 3–7) were isolated. The structures of the two new compounds were identified by their physicochemical properties and spectral analysis, particularly one- and two-dimensional nuclear magnetic resonance spectral methods.(Author for correspondence.Tel: 021-50272221; Fax: 021-50272221; E –mail:simmhulh@mail.shcnc.ac.cn)