RESUMEN
Four new 19-nor-clerodane diterpenoids (1-4), one new 15,16-dinor-ent-pimarane diterpenoid (5) together with four known diterpenoids (6-9) were isolated from whole plants of Croton yunnanensis. The structures of these compounds were determined by extensive spectroscopic methods including 1D, 2D NMR, HR-ESI-MS, and by comparing their NMR data with those of previously reported compounds. The experimental and calculated electronic circular dichroism data were used to define their absolute configurations. The 1H and 13C NMR spectra of 6 were completely assigned for the first time. All isolated compounds (1-9) were evaluated for their cytotoxic activities against five human cancer cell lines (including SMMC-7721, HL-60, A-549, MCF-7, and SW-480), and anti-inflammatory activities in LPS-induced RAW264.7 macrophages. Crotonyunnan E (5) exhibited selective cytotoxicities against three tumor cell lines, SMMC-7721 (human hepatoma cells, IC50 4.47 ± 0.39 µM), HL-60 (human premyelocytic leukemia, IC50 14.38 ± 1.19 µM), and A-549 (human lung cancer cells, IC50 27.42 ± 0.48 µM), while none of the compounds showed obviously anti-inflammatory activities at 50 µM level.