Five new sesquiterpenoids from Parasenecio petasitoides

From the whole plants of Parasenecio petasitoides, five new sesquiterpenoids were isolated, (E,E)-3alpha,9beta-dihydroxy-6betaH,11betaH-13-norgermacra-1(10),4-dien-11,6-carbolactone (2), (E,E)-2alpha,9beta-dihydroxy-6betaH,11betaH-13-norgermacra-1(10),4-dien-11,6-carbolactone (3), (E,E)-2alpha,9beta-dihydroxy-6betaH,11alphaH-13-norgermacra-1(10),4-dien-11,6-carbolactone (4), (E)-15-hydroxy-2-oxo-6betaH,11alphaH-13-norguaia-3-ene-11,6-carbolactone (7), and (E)-11beta,15-dihydroxy-2-oxo-6betaH-13-norguaia-3-ene-11,6-carbolactone (8), together with three known compounds, deacetyl herbolide A (1), jacquilenin (5), and (E)-15-hydroxy-2-oxo-6betaH,11betaH-13-norguaia-3-ene-11,6-carbolactone (6). The structures of these natural products were elucidated spectroscopically, especially by 1D- and 2D-NMR techniques, in combination with high-resolution mass spectroscopy.