New Eremophilane Sesquiterpenes from the Roots of Ligularia fischeri

New eremophilane sesquiterpenes, (3 beta,6 beta,8 alpha,10 beta)-3-acetyl-6,8,10-trihydroxyeremophil-7(11)-eno-12,8-lactone (1), (3 beta,6 beta,8 beta,10 beta)-3-acetyl-8,10-dihydroxy-6-(2-methyl-1-oxobutoxy) eremophil-7(11)-eno-12,8-lactone (2), (3 beta,6 beta,10 beta)- and (3 beta,6 beta,10 alpha)-3-acetyl-6,10-dihydroxyeremophila-7(11),8-dieno-12,8-lactone (3 and 4, resp.), and a dinoreremophilane derivative, (3aR,4R,5S,7aS)-2-acetyl-3a,4,5,6,7,7a-hexahydro-7a-hydroxy-1H-inden-5-yl acetate (5), were isolated from the roots of Ligularia fischeri. Their structures were elucidated by spectroscopic methods including 1D and 2D NMR spectra, and the structure of 1 was further confirmed by a single-crystal X-ray diffraction experiment. Among the isolated compounds, lactone 1 exhibited inhibitory activity towards PTP1B with an IC50 value of 1.34 mu M in vivo. The other compounds were inactive.