A new eremophilanolide from Senecio sinuatus Gilib.

From the hexane extracts of Senecio sinuatus roots, the new 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-en-8beta,12-olide (3), along with the known compounds 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-ene (1), 3beta-senecioyloxy-6beta-hydroxyeremophil-1(10)-ene (2), and 3beta-angeloyloxy-6beta,8alpha-dihydroxyeremophil-1(10)-en-8beta,12-olide (4), were isolated. Complete 1H and 13C NMR chemical shift assignments of 1-4 were achieved using one- and two-dimensional NMR techniques, including gHMQC and gHMBC experiments. A Monte Carlo search, followed by B3LYP/6-31G*DFT calculation, provided the theoretical conformations of the eremophilane rings, which were in agreement with results derived from 1H-1H NMR coupling constant analysis, and confirmed by NOESY experiments.