New weakly cytotoxic eremophilane sesquiterpenes from the roots of Ligularia virgaurea.

Six new eremophilane sesquiterpenes, including a novel nortrieremophilane carbon skeleton, were isolated from the roots of Ligularia virgaurea. Their structures were elucidated as 3 alpha,4 alpha-epoxy-6 alpha-(2'-methylacryloyl)oxy-8 alpha-methoxyeremophil-7(11)-en-8 beta,12-olide (1), 3 alpha,4 alpha-epoxy-6 alpha-(2'-methylacryloyl)oxy-8 alpha-ethoxyeremophil-7(11)-en-8 beta,12-olide (2), 1 beta,10 beta-epoxy-6 beta-(2'-methylacryloyl)oxy-8 beta-methoxyeremophil-7(11)-en-8 alpha,12-olide (3), 1 beta,10 beta-epoxy-6 beta-angeloyloxy-8 beta-methoxyeremophil-7(11)-en-8 alpha,12-olide (4), 6 beta-methoxyeremophil-7(11)-en-8 beta,12-olide (5), and 5 beta-angeloyloxy-3a,4,5,6,7,7a-hexahydro-3a beta-methyl-1 H-indene-2,4 beta-dioic acid methyl ester (6) by spectral methods, including IR, HR-ESI-MS, 1D and 2D NMR techniques. All of compounds were evaluated for their in vitro cytotoxic activities against human hepatoma (SMMC-7721), human promyelocytic leukemia (HL-60), and human hepatocyte (L-02) cells.